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Types of Routing Protocols – Explained 

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types of routing
types of routing

Routing is a process of selecting the best possible paths for data packets to travel from a source to a destination in a network. Routing is performed by layer 3 devices like routers and multi-layer switches. 

What are the different types of Routing?

Routing protocols can be broadly categorized into three types:-  

  1. Static Routing  
  2. Default Routing  
  3. Dynamic Routing  

Let us try to understand each type in brief. 

What is Static Routing Protocol?

Static Routing is a process in which the network administrator will determine the path to reach unknown networks. So, in the case of static routing, the network administrator will configure the router’s routing table manually.  

In case any change occurs in a network, the administrator has to reconfigure the route, and changes do not take place automatically. Static routing is simple to configure and suitable for small-scale enterprises. 

How to configure Static Routing?

Static Routing can be configured in two ways, namely- 

  • Static Routing with the Next Hop 

In this type of static routing, the network administrator will tell the router about the next hop address, i.e., the neighboring router interface IP to reach a particular network. 

Syntax for static routing with the next hop: 

Enter Global configuration mode. 

Device# configure terminal

Device (config)# ip route <Destination N/W IP> <Destination subnet mask> <Next hop IP address> 

  • Static Routing with an Exit Interface 

In this case, the network administrator will configure the router about the interface from which a packet will exit for an unknown network. Most commonly, this protocol is used when routers are connected with a serial cable. The serial cable does not use the Mac address. 

NOTE: If Mac addresses are not used, then proxy ARP will not be generated.   

Syntax for static routing with an exit interface: 

Enter Global configuration mode. 

Device# configure terminal

Device(config)# ip route <Destination N/W IP> <Destination Subnet Mask> <Exit interface> 

Configuration:- Let us take an example of a small topology given in the figure. 

R1 

 

Shape 

R1#config t 

R1(config)#ip route 172.17.0.0 255.255.0.0 1.1.1.2 

 

R2 

 

R2#config t 

R2(config)#ip route 172.16.0.0 255.255.0.0 1.1.1.1 

 

 

Verification: – 

 

R1#show ip route  

Codes:

L – local, C – connected, S – static, R – RIP, M – mobile, B – BGP

D – EIGRP, EX – EIGRP external, O – OSPF, IA – OSPF inter area

N1 – OSPF NSSA external type 1, N2 – OSPF NSSA external type 2

E1 – OSPF external type 1, E2 – OSPF external type 2, E – EGP

i – IS-IS, L1 – IS-IS level-1, L2 – IS-IS level-2, ia – IS-IS inter area

* – candidate default, U – per-user static route, o – ODR

P – periodic downloaded static route 

 

The Gateway of last resort is not set.

1.0.0.0/8 is variably subnetted, 2 subnets, 2 masks 

C 1.0.0.0/8 is directly connected, GigabitEthernet0/0/0 

L 1.1.1.1/32 is directly connected, GigabitEthernet0/0/0 172.16.0.0/16 is variably subnetted, 2 subnets, 2 masks 

C 172.16.0.0/16 is directly connected, GigabitEthernet0/0/1 

L   172.16.1.1/32 is directly connected, GigabitEthernet0/0/1 

S 172.17.0.0/16 [1/0] via 1.1.1.2 

 

R2#show ip route  

Codes:

L – local, C – connected, S – static, R – RIP, M – mobile, B – BGP 

D – EIGRP, EX – EIGRP external, O – OSPF, IA – OSPF inter area 

N1 – OSPF NSSA external type 1, N2 – OSPF NSSA external type 2 

E1 – OSPF external type 1, E2 – OSPF external type 2, E – EGP 

i – IS-IS, L1 – IS-IS level-1, L2 – IS-IS level-2, ia – IS-IS inter area 

* – candidate default, U – per-user static route, o – ODR 

P – periodic downloaded static route 

 

The Gateway of last resort is not set. 

1.0.0.0/8 is variably subnetted, 2 subnets, 2 masks 

C 1.0.0.0/8 is directly connected, GigabitEthernet0/0/0 

L 1.1.1.2/32 is directly connected, GigabitEthernet0/0/0 

S 172.16.0.0/16 [1/0] via 1.1.1.1  

172.17.0.0/16 is variably subnetted, 2 subnets, 2 masks 

C 172.17.0.0/16 is directly connected, GigabitEthernet0/0/1 

L 172.17.1.1/32 is directly connected, GigabitEthernet0/0/1 

What are the advantages of Static Routing Protocol?

The advantages of the Static Routing Protocol are as follows:-  

  1. Easy to implement as compared to dynamic routing  
  2. Less overhead on the router means minimizing the utilization of the device.

What are the disadvantages of Static Routing Protocol?

The disadvantages of the Static Routing Protocol are as follows:-  

  1. It is not suitable to configure on a large network because the administration has to configure it manually.  
  2. If there are changes in the network, like a new router being added or a network being removed, then the static entry must be added or removed accordingly.  
  3. Recursive Lookup: When a routing table is checked more than once for a packet, this is known as a recursive lookup. This is a disadvantage with static routing with the next hop. 

What is Default Routing Protocol?

When a router does not have the specific route entry for the destination network, default routing is used to forward packets to a default gateway or next-hop router. In other words, a router will send a packet to a preconfigured default gateway if the packet’s destination IP address doesn’t match any of the routes it has configured.  

NOTE: Default routing is the type of static routing in which all the packets will be forwarded by matching the default entry in the routing table.  

This routing protocol is mainly used at the edge router of the enterprise  

There is a high chance of creating a loop in the network by default routing so we have to use default routing carefully. 

Syntax:  

 

Enter Global configuration mode. 

Shape 

Device# configure terminal 

Device(config)# ip route 0.0.0.0 0.0.0.0 <Next Hop IP Address> 

 

Configuration: – Let us configure the default route on the same topology   

R1#config t 

R1(config)#ip route 0.0.0.0 0.0.0.0 1.1.1.2 

 

Verification: 

 

 

R1#show ip route 

Codes: L – local, C – connected, S – static, R – RIP, M – mobile, B – BGP 

D – EIGRP, EX – EIGRP external, O – OSPF, IA – OSPF inter area 

N1 – OSPF NSSA external type 1, N2 – OSPF NSSA external type 2 

E1 – OSPF external type 1, E2 – OSPF external type 2, E – EGP 

i – IS-IS, L1 – IS-IS level-1, L2 – IS-IS level-2, ia – IS-IS inter area 

* – candidate default, U – per-user static route, o – ODR 

P – periodic downloaded static route 

 

Gateway of last resort is 1.1.1.2 to network 0.0.0.0 

 

 1.0.0.0/8 is variably subnetted, 2 subnets, 2 masks 

ShapeC 1.0.0.0/8 is directly connected, GigabitEthernet0/0/0 

L 1.1.1.1/32 is directly connected, GigabitEthernet0/0/0 

 172.16.0.0/16 is variably subnetted, 2 subnets, 2 masks 

C 172.16.0.0/16 is directly connected, GigabitEthernet0/0/1 

L 172.16.1.1/32 is directly connected, GigabitEthernet0/0/1 

S* 0.0.0.0/0 [1/0] via 1.1.1.2 

 

Similarly, for R2: 

 

 

R2(config)#ip route 0.0.0.0 0.0.0.0 1.1.1.1 

 

Verification: –  

 

R2#show ip route 

S* 0.0.0.0/0 [1/0] via 1.1.1.1 

What are the advantages of Default Routing Protocol?

The advantages of Default Routing Protocol are as follows:-   

  1. Default routing simplifies the routing configuration by providing a single route for the network.  
  2. Reduction in routing table size  
  3. Easy to configure 

What are the disadvantages of Default Routing Protocol?

The disadvantages of the Default Routing Protocol are as follows:-  

  1. If an unauthorized device or attacker gains control of the default route, they could potentially divert traffic inappropriately.  
  2. If a default route is misconfigured or points to an incorrect next hop, it can lead to traffic being misrouted or dropped.  
  3. In complex networks with diverse destinations and traffic patterns, default routing might not effectively accommodate all routing requirements. 

What is Dynamic Routing Protocol?

Configuring Static Routing and Default Routing is hectic, and when it comes to a large number of routes, it is not easy to configure each route manually. Dynamic Routing can automate this process. 

Dynamic Routing protocols allow routers to dynamically learn and adapt to changes in the network topology. These protocols use algorithms to calculate the best path for packet forwarding based on various factors such as network congestion, link availability, and cost metrics. 

Examples of dynamic routing protocols include RIP, OSPF, EIGRP, and BGP.

What are the kinds of Dynamic Routing Protocols?

Dynamic Routing can be divided into two types, namely- 

  • Interior Gateway Protocol (IGP) 

IGP is designed and intended for use inside a single autonomous system.  

IGP is further divided into multiple types- 

  1. Distance vector routing protocol (DVRP): – Routing Internet protocol (RIP), Interior gateway routing protocol (IGRP)  
  2. Advanced distance vector routing protocol (ADVRP): – Enhance interior gateway routing protocol (EIGRP)  
  3. Link state routing protocol (LSRP): – Open shortest path first (OSPF), IS-IS (Intermediate system-intermediate system). 

  • Exterior Gateway Protocol (EGP) 

EGP is designed to be used between the same as well as different autonomous systems over the internet.  

NOTE: Path vector routing protocol (PVRP) i.e. Border gateway protocol comes under this category. 

What are the advantages of Dynamic Routing Protocol?

The advantages of Dynamic Routing Protocol are as follows:-   

  1. Dynamic routing protocol can automatically update the routing table in response to changes in the network. Hence, manual work is reduced.  
  2. This protocol can easily adapt to network changes by recalculating routes which makes it suitable for networks with dynamic traffic patterns.  
  3. It provides fast convergence. 

What are the disadvantages of Dynamic Routing Protocol?

The disadvantages of the Dynamic Routing Protocol are as follows:-  

  1. Configuring dynamic routing protocol is very complex. 
  2. Dynamic protocol generates routing updates which leads to the utilization of bandwidth, processing power, etc.  
  3. Security risk is high. 

What is NTP? Explained in Detail 

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what is ntp
what is ntp

On routers and switches, we can even configure time and date locally but in a network with a large amount of network devices, it becomes difficult to configure time and date and even to manage it individually. If time is wrongly configured it can lead to inaccuracies in failure logs etc.  

To configure it accurately over a large network, we need some dynamic protocol and here Network Time Protocol (NTP) comes to the rescue.  

NTP- Network Time Protocol is a networking protocol used for synchronizing the clocks of computer systems over a packet-switched network. It works on the client-server model. NTP helps in coordinating and maintaining accurate time among a set of distributed time servers and clients in a network.

What are the functions of NTP?

Some important functions of the Network Time Protocol are as follows: –

  • Time Synchronization: – NTP ensures that all devices on a network agree on the current time. It achieves this by synchronizing the clocks of various devices with reference time sources known as an NTP server.  
  • Hierarchical Structure: – NTP operates hierarchically with the level of time servers. These levels are also known as strata. Stratum 0 devices are exact reference clocks. Some examples are atomic clocks or GPS clocks. Stratum 1 devices are directly synchronized to Stratum 0 devices. Stratum 2 devices synchronize to stratum 1 devices and the hierarchy goes on.  
  • Timestamps and Round-Trip Delay: – NTP uses timestamps to measure the propagation delay between devices accurately. By exchanging timestamps, NTP calculates the offset between device clocks and compensates for network delays.  
  • Clock Discipline algorithm: – NTP implements a sophisticated clock discipline algorithm to adjust the system clock rate gradually, ensuring smooth and accurate time synchronization. it takes into account factors such as clock drift, jitter, and network latency.  
  • NTP modes of operations: – NTP operates in various modes, including client/server and peer-to-peer modes. In client/server mode, client devices synchronize their clocks with a designated NTP server. In peer-to-peer mode, devices can act as clients and servers, exchanging time information with peers.  

How NTP works?

  • Time synchronization request: – A client sends a request to an NTP server, requesting the current time.  
  • Timestamp exchange: – The NTP server responds with its current time and includes its timestamp in the response packet.  
  • Clock Synchronization: – The client uses the information received from the server, including the server’s timestamp and round-trip delay, to adjust its local clock, minimizing the time discrepancy.  
  • Periodic Updates: – NTP continuously exchanges time information between servers and clients to maintain synchronization and compensate for clock drift.

What are the benefits of NTP?

  • Accurate Timekeeping: – NTP helps in accurately synchronizing time across the devices that are critical for various applications including financial transactions, network security, and distributed computing.  
  • Reduced errors and inconsistencies: – Ensure that logs, timestamps, and distributed systems operate with synchronized time, minimizing errors and inconsistencies.  
  • Security enhancement: – Helps in securing systems by providing accurate time for cryptographic operations, certified validity checks, and authentication protocols.  

What is NTPv4 and what are its advantages?

Network Time Protocol version 4 is the current and most widely used version of network time protocol. It is an updated and enhanced version compared to its predecessors, with more improved accuracy, security, and functionality. Some advantages of NTPv4 are: –

  • Improved Accuracy: – NTPv4 offers enhanced accuracy in time synchronization by utilizing sophisticated algorithms and mechanisms to reduce clock drift and maintain precise time across the network.  
  • Security Enhancements:- NTPv4 includes improvements in security features offering better protections against various attacks and vulnerabilities compared to earlier versions. It introduces authentication mechanisms such as symmetric key cryptography (MD5 and SHA-1) and auto-key for cryptographic key management, enhancing the integrity and authenticity of time synchronization messages.  
  • Extension fields: – NTPv4 supports extension fields in its protocol structure, allowing for flexibility and future scalability to accommodate additional; functionalities or information without compromising compatibility with older versions.  
  • Compatibility: – While introducing new features and improvements, NTPv4 maintains backward compatibility with earlier versions of NTP, ensuring a smooth transition and interoperability across diverse systems and devices.  
  • IPV6 support: – NTPv4 is designed to work seamlessly with IPv6 networks, supporting both IPv4 and IPv6 addressing which makes it adaptable even for modern network infrastructure.  
  • Algorithm for clock selection: – NTPv4 introduces algorithms for clock selection and combining time sources, enhancing the ability to choose the most accurate and reliable time sources among multiple available options.  
  • Improved monitoring and diagnostics: – NTPv4 provides enhanced monitoring and diagnostic capabilities, allowing administrators to better analyze time synchronization performance and diagnose issues within the network. 

What is the Difference Between SNTP and NTP?

Simple Network Time Protocol and Network Time Protocol are related protocols used for time synchronization with some differences in functionality and features which are discussed below. 

Simple Network Time Protocol 

Network Time Protocol 

SNTP is a simplified version of NTP. It is designed to provide basic time synchronization capabilities without the full complexity and overhead of the complete NTP implementation. 

NTP is a more comprehensive and advanced protocol designed to provide accurate time synchronization across a network. It offers more precious timekeeping than SNTP. 

SNTP lacks some advanced features present in NTP. it typically does not include features like stratum and sophisticated clock synchronization algorithms. 

NTP includes advanced functionalities like stratum levels, symmetric and asymmetric key authentication, cryptographic security mechanism, precision timekeeping algorithms and clock disciplining to minimize clock drift. 

SNTP is less precise and does not provide the same level of accuracy as NTP. 
 

NTP achieves accuracy with the help of complex algorithms to account for network delays and select the best time sources available. 
 

Since SNTP does not employ extensive algorithms for time synchronization, it is less resource-intensive compared to NTP 

NTP with advanced features is CPU intensive and requires higher processing units as compared to SNTP 

SNTP does not authenticate traffic hence SNTP client is prone to attacks and should only be used where no strong authentication or security is required. 

NTP clients authenticate traffic from NTP servers and hence it is more secure. 

SNTP uses a method known as stepping. SNTP adjusts time at some fixed interval and not continuously as in the case of NTP. Servers are configured to send out time at some fixed interval. Also, time can be out of sync by 100 milliseconds. 

NTP servers continuously send out timestamps to NTP clients. NTP even calculates and adjusts the time error caused by latency using the algorithms. This process which helps NTP clients to syn exact time is known as time skewing. 

It is suitable for scenarios where full-featured time synchronization is not critical such as embedded systems, IoT devices, or applications that do not require highly accurate time logs. 

NTP is used where precise and highly accurate time synchronization is essential such as in financial networks, telecommunications, scientific research, and other applications requiring strict time accuracy. 

SNTP is an old protocol that was released for low-processing unit devices back then. Today devices are equipped with high-end processors that can easily adapt NTP. SNTP cannot be used at places where accurate time is required, for example, UPI transactions, financial services, etc. Hence NTP becomes a better choice over SNTP. 

What is Quality of Service: A Comprehensive Guide

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what is quality of service
what is quality of service

Quality of service refers to a set of techniques and mechanisms used to manage and prioritize network traffic to ensure the performance, reliability, and availability of the packets in the network. QOS helps to set priority for the type of data packets. Key aspects of QoS include traffic prioritization, bandwidth management, latency control, packet loss mitigation, traffic shaping, and congestion management. QOS mechanism enables allocating resources such as bandwidth to critical applications or services ensuring they receive adequate network resources for optimal performance.

By implementing QoS, network administrators can ensure that essential applications (e.g. voice and video communication) receive higher priority and better treatment, with less sensitive traffic operating efficiently without causing congestion or impacting critical services. QoS helps achieve better network efficiency, reliability, and user satisfaction by providing a consistent and optimized user experience across the network.  

Below are the parameters that can be controlled and managed by QoS- 

  • Packet loss: – Packet loss refers to the failure of data packets to reach their destination in a network. It occurs when packets are dropped or discarded during transmission often due to network congestion, hardware issues, or errors. Excessive packet loss can degrade network performance and affect the quality of real-time applications like VoIP or video streaming.  
  • Jitter: – Jitter is the variation in the delay of received packets in a network, It represents the deviation in packet arrival times caused by network congestion, varying routes, or different queuing delays. In real-time communication applications, high jitter can cause disruptions delays, or inconsistent quality in audio or video streams.  
  • Latency: – Latency refers to the time it takes for data packets to travel from a source to a destination across a network. It includes various components such as transmission, delay propagation delay, queuing delay, and processing delay. High latency can result in delays and sluggishness in network communications and can impact the responsiveness of the application.  
  • Bandwidth: – Bandwidth refers to the maximum data transfer rate of a network connection or channel. It measures the capacity of the network to transmit data over a specified period, typically expressed in bits per second. Higher bandwidth allows more data to be transferred within a given time frame, facilitating faster communication and higher throughput.  
  • Mean Opinion Score (MOS): – MOS is a measure used to assess the perceived quality of audio or video in communication systems. It represents the average opinions of multiple listeners or viewers regarding the quality of media content. MOS values range from 1 to 5 with higher scores indicating better quality. MOS is commonly used in evaluating the quality of voice calls, video calls, video conferences, and multimedia streaming. 

How does QOS work?

QoS works by implementing various techniques within a network to manage and prioritize different types of traffic. Below are some the points explaining how Quality of service works: –

  • Traffic Classification: – QoS starts by identifying and classifying different types of network traffic based on their characteristics such as source/destination addresses, port numbers, protocols, or specific application requirements. This classification helps in distinguishing between various types of traffic.  
  • Traffic prioritization: – Once traffic is classified, QoS assigns priorities or levels of importance to different classes of traffic, Critical applications like voice or video conferencing might be assigned a higher priority than less time-sensitive traffic like file downloads.
  • Traffic shaping and policing: – The QoS mechanism includes traffic shaping and policing to control the flow of data and manage bandwidth utilization. Traffic shaping smooths out a burst of traffic to prevent congestion while traffic policing enforces traffic limits based on predefined rules.
  • Queuing and Scheduling: – QoS employs queuing and scheduling algorithms to manage the order in which packets are transmitted when network congestion occurs. These algorithms prioritize and schedule packets according to their assigned priorities or classes.
  • Bandwidth Allocation and Reservation: – The Quality-of-service mechanism allocates and reserves specific amounts of bandwidth for high-priority traffic ensuring that critical applications receive the necessary resources for optimal performance. Bandwidth allocation can be dynamic or static depending on the requirements.
  • Congestion Management: – QoS helps in managing and mitigating network congestion by using techniques like traffic prioritization, congestion avoidance mechanisms, and buggering to prevent or minimize congestion-related issues.
  • Quality parameters:- QoS typically involves defining and monitoring quality parameters such as latency, jitter, and packet loss, These parameters are continuously monitored and QOS mechanisms work to ensure that they stay within acceptable limits for different types of traffic.
  • Enforcement and control:- QoS policies are enforced across network devices such as routers switches and firewalls using configuration settings, Network administrators configure QoS policies based on the specific requirements of the network and the applications running on it. 

Why Quality of service is important?

QOS is important and is widely used for the following reasons- 

  • Prioritization: – QoS helps in prioritization of important services and applications over less sensitive traffic. It ensures that essential services like VoIP, video conferencing, and other sensitive traffic receive the necessary network resources minimizing delays and ensuring reliable performance.
  • Improved user experience: – By prioritizing and managing network traffic, QoS helps maintain a consistent and optimized user experience. It reduces latency and packet loss ensuring smoother and more reliable communication for real-time applications
  • Bandwidth Management: – QoS enables efficient allocation and management of available network bandwidth. It ensures that network resources are used effectively preventing network congestion and optimizing data transfer for different types of traffic.
  • Optimized Network Performance: – Implementing a QoS mechanism helps in optimizing overall network performance by preventing bottlenecks reducing latency and ensuring that critical services have the necessary resources to function smoothly.
  • Maintaining Service level agreements (SLAs): – In an enterprise or service provider environment QoS is essential for meeting SLAs. It allows organizations to guarantee specific levels of performance and reliability for their services meeting the expectations of the customers.
  • Supporting Diverse applications: – Today’s network handles diverse types of traffic including voice, video, data, and IoT applications. QoS ensures that these various applications coexist simultaneously by providing each with the required performance parameters. 

What are the types of delays?

  • Propagation delay: – The time taken for a signal or data packet to travel from the sender to the receiver. It’s primarily determined by the distance between the two points and the speed of propagation into the transmission medium (fiber optic cable, copper wire, etc).
  • Serialization delay: – Serialization delay refers to the time it takes to transmit an entire packet’s bits onto the network medium or link. It is determined by the size of the packet and the transmission rate (bandwidth) of the link. Larger packets take longer to transmit than smaller ones and higher transmission rates reduce serialization delay. The following equation is used to calculate serialization delay

Serialization delay (in seconds) = Packet size (in bits)/ transmission rate (in bits per second)

  • Shaping delay: – Shaping delay is a delay introduced deliberately by the traffic shaping mechanisms in network devices such as routers and switches. Traffic shaping is used to control the rates of data transmission, smoothing outbursts of traffic to prevent congestion and ensure that network traffic conforms to predefined traffic profiles or limits. Shaping delay is introduced to regulate and shape the flow of traffic, often by buffering packets temporarily before transmitting them. By controlling the rate of transmission, it ensures that network traffic remains within specified bandwidth limits, preventing congestion and optimizing network performance.
  • Processing delay: – The time taken by routers, switches, or other network devices to process and examine the packet headers make forwarding decisions, and perform necessary operations like error checking routing lookups, or security checks.
  • Queuing Delay: – The time a packet spends waiting in a queue at a network device, router, or switch before it can be transmitted. This delay occurs when there’s congestion or high traffic and packets have to wait for their turn to be forwarded.

What are VLAN and QinQ?: Explained 

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What are VLAN QinQ?
What are VLAN QinQ?

What is an Ethernet Frame? 

An Ethernet frame is a fundamental unit of data transmitted over an Ethernet network. It contains the necessary information for data to be transmitted from one device to another within a local area network. Ethernet frames consist of various fields each serving a specific purpose in facilitating communication across the network. 

What is an Ethernet Frame?

Key components of an Ethernet frame include: -

Preamble: – It is a sequence of alternating 1s and 0s used to synchronize the receiver’s clock with the sender’s clock. It prepares the receiver to expect incoming data. 

Start Frame delimiter (SFD): – Marks the end of the preamble and signals the start of the frame. It helps the receiver identify the beginning of the frame’s data section. 

Destination MAC Address: – A 6-byte field identifying the intended recipient device’s Media Access Control (MAC) address. 

Source MAC Address: – A 6-byte field identifying the MAC Address of the sending device. 

EtherType or Length Field: – EtherType indicates the type of protocol carried in the Ethernet frame, such as IPv4 or IPv6 or others. In cases where EtherType is used, the field indicates the data length in the frames. 

Payload: – The actual data being transmitted can vary in length and content. It typically includes the higher-layer protocol data (such as IP Packets, TCP segments, or UDP datagram) encapsulated within the Ethernet frame. 

Frame check sequence (FCS): – A field containing error-checking information, usually a cyclic redundancy check (CRC) to detect any errors that might have occurred during transmission. 

What is VLAN and how does VLAN tagging work?

VLAN, also known as Virtual Local Area Network, is a networking technology that helps to segment a single physical network into multiple separate logical networks. We have already discussed VLAN and its configuration earlier. Here let’s focus on VLAN tagging and its effect on the Ethernet header. 

Let us take the example of the below topology to understand how VLAN tagging changes the Ethernet Header and why it is used. 

What is VLAN and how does VLAN tagging work?

We have 4 host H1, H2, H3 and H4 and two switches S1 and S2 connecting these host 

H1 and H3 are in VLAN 1 while H2 and H4 are in VLAN 2 and Host H1 needs to communicate with Host H3.  

H1 generates a packet that needs to be destined to H3. When this packet arrives S2, S2 needs to know whether this packet belongs to H3 or H4 i.e. VLAN 1 or VLAN 2. 

When the host generates a packet, the data frame looks like given below; – 

Key components of an Ethernet frame include

Notice that the ethernet frame does not have any information regarding the VLAN tagged. 
When a switch receives the ethernet frame, and since that port is already configured with a particular VLAN, the switch adds additional VLAN information known as VLAN tagging. 

data frame

S2 now receives a packet with VLAN tagged to the ethernet frame and now knows that the packet belongs to VLAN 1. Switch then removes the additional header from the ethernet frame and forwards the frame to the Host 3. 

The VLAN tagging is done with the help of a standard known as IEEE802.1Q. 

What are IEEE standards?

IEEE stands for Institute of Electrical and Electronics Engineers. It is a global professional organization composed of engineers, scientists, and professionals dedicated to advancing technology in various fields including electrical engineering, electronics engineering, telecommunication, etc. 

IEEE has various networking and telecommunication standards such as IEEE 802.11 which is used for WIFI, IEEE 802.3 which is standard for ethernet, IEEE 802.15 which is standard for Wireless Personal Area Networks.  

What is 802.1Q?

IEEE 802.1Q also known as VLAN tagging is a standard defining a method for inserting VLAN membership information into the Ethernet Frame. It is a part of the 802.1 group of standards that focus on network bridging and management. 

802.1Q provides a mechanism for identifying VLAN membership of Ethernet frames. It adds a 4-byte tag, called a VLAN tag or VLAN header to the Ethernet Frame’s header. This VLAN tag includes information such as VLAN ID, priority, quality of service, etc.

 VLAN tagging is crucial for carrying VLAN information across network devices like switches, routers, and other networking equipment. It allows the transmission of multiple VLANs over a single network link known as trunk effectively extending VLANs across the network infrastructure. 

802.1Q is an open-source standard and supported by multiple vendors and it is a popular standard used for VLAN tagging. 

The most important use of this standard is the qinq tunneling also called double tagging. 
It is used to encapsulate multiple VLANs within other VLANs. it enables the service provider to transport customer VLAN transparently across their networks by adding a VLAN tag. 

What is ISL?

ISL stands for InterSwitch link. I was a proprietary VLAN trunking protocol developed by Cisco before the IEEE802.1Q standards for VLAN tagging and can only be used on Cisco devices. 
 
ISL serves the same purpose that the 802.1Q serves but it cannot be used on other vendor devices hence with the introduction of the IEEE802.1Q standard for VLAN tagging, ISL become less popular.  
ISL also does not support the feature of QinQ tunneling which was introduced by 802.1Q 

What is QinQ tunneling?

The QinQ supports feature adds another layer of IEEE 802.1Q tag also known as metro tag or PE-VLAN to the 802.1Q tagged packets that enter the network.  
QinQ tunneling involves the insertion of an additional VLAN tag (outer tag) into an Ethernet frame, allowing the transmission of multiple VLANs across a provider’s network infrastructure. This technique is primarily used in service provider networks, especially in metro Ethernet and carrier-grade Ethernet networks. 

QinQ tunneling is commonly used by service providers to transport multiple customer’s VLAN traffic over a single physical link or network. It enables segmentation and isolation of customer traffic while using a shared provider network infrastructure.

 Frames encapsulated using QinQ tunneling have two sets of 802.1Q tags, the outer tag (service provider’s VLAN) and inner tag (Customer’s VLAN) allowing the provider to maintain VLAN separation and manage traffic accordingly. 

Hence, QinQ tunneling is helpful when there are multiple overlapping VLAN IDs between customers and it is used in large enterprise or service provider networks. QinQ is used to facilitate the encapsulation of multiple VLANs within another VLAN. It extends the capabilities of IEEE802.1Q VLAN tagging by allowing the stacking or nesting of VLAN tags. 

VLAN tags

We have already understood the Ethernet Frame and the tagged Ethernet frame and how it looks like the tagged frame is known as the 802.1Q frame. With the help of the 802.1Q standard, we can add one more tag to the already tagged ethernet frame.  
Let us take an example to further understand the use of QinQ tunneling In the service provider network 

service provider network

We have offices of Customer A and Customer B at Sites 1 and Site 2 and Customer A wants to share traffic between Site 1 and Site 2. Similarly, Customer B wants to communicate between Site 1 and Site 2. 

Switch at Site 1 tagged the packet with VLAN ID 10 and Switch of customer B also tagged the packet with VLAN ID 10. As we can see the case of VLAN overlapping. 

Now to differentiate between the customers, the service provider edge switch adds another tag to the already tagged packet. Tags assigned by the service provider will be different for every customer which helps to differentiate the traffic of each customer and in this case, QinQ tunneling is used since VLAN is tagged on an already tagged Ethernet Frame. 

What are the Firewall Functions: Explained

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firewall functions
firewall functions

A firewall is a device or software application that is used for network security. It helps to monitor and control the incoming and outgoing network traffic based on some pre-defined security policies Its purpose is to establish a barrier between a trusted internal network and an untrusted external network such as the internet and to prevent unauthorized access while allowing the authorized communication to pass through. So it functions by creating a trusted and untrusted zone. Most firewalls allow traffic from the trusted zone (authorized zone) to the untrusted zone but traffic from the untrusted zone to the trusted zone is denied. 
Firewalls also have a less trusted zone which is called a Demilitarized zone. 

Demilitarized zone.

Some value is assigned to the interface of these zones and the traffic from lower security value is not allowed to the higher security value by default and requires some permission. But the traffic from a higher security zone is allowed to the lower security zone. The flow of traffic can be manipulated as per the need. 

firewall
firewall

What are the key functions of a firewall?

Network Security: A firewall acts as the first line of defense against cyber threats, malicious attacks, and unauthorized access attempts from the internet or untrusted zone/network. A firewall helps in monitoring incoming and outgoing traffic, filtering and blocking potentially harmful or suspicious data packets based on predefined security rules. 

Access Control:- Firewalls implement access control policies allowing administrators to define and manage rules that determine which network traffic is permitted or denied. This control helps in regulating who and what can access the network, safeguarding against unauthorized users and potential threats.  

Protection of sensitive data: A firewall helps in protecting the sensitive data and resources within a network by preventing unauthorized access to confidential information, proprietary data, personal details, or financial records. By controlling access to resources, firewalls help maintain data confidentiality and integrity. 

Prevention of malware and cyber attacks:- Firewalls help prevent malware viruses worms, ransomware, and other malicious software from infiltrating the network by blocking known malicious traffic patterns or infected files from entering the system. 

Network Segmentation:- They Facilitate network segmentation by dividing the network into separate zones or segments each with its security policies. This isolation helps contain potential threats and limit the impact of security breaches. 

Compliance and regulatory requirements:- Many industries have specific security standards and compliance regulations that require the implementation of firewalls as part of their security measures. Compliance with these standards ensures adherence to security best practices. 

Protection of Endpoint:- In addition to network-level protection firewalls on individual devices or endpoint firewalls offer an additional layer of security by monitoring traffic specific to that device and preventing unauthorized access or attacks targeting the endpoint. 

What are the types of firewalls?

  • Packet filtering firewall: – This type of firewall operates at the OSI model’s network layer (Layer 3). As the name suggests, it uses the packet filtering technique to provide network security, and some predefined rule is configured on the firewall. When a packet arrives at the firewall, it examines the packet header including information on the source and destination IP Address, source port, destination port, protocol type, etc. Firewalls then look at the predefined policy, compare the information, and make the decision whether to allow or deny the packet.  
    Also, packet filtering firewalls operate in a stateless manner which means that they evaluate each packet individually without considering the packet’s relationship to previous or subsequent packets. They do not maintain a state table or keep track of the state of connections like in the case of stateful inspection firewalls do. 
    Based on the rules, the firewall decides to permit the packet to pass through (allow) drop the packet (deny), or possibly log information about the packet for auditing purposes. 
    One thing to remember is the order of the rule list. The list is always viewed from top to bottom. Thus, more important rules must always be placed at the top.  
    For example: – 

Rule 1:- Allow Destination Address 172.16.1.5  

Rule 2:- Deny Destination Address 172.16.1.5  

since the rule list is viewed from top to bottom, the packet with destination address 172.16.1.5 will be allowed even though you have denied it in rule 2. 

Hence the order of rule is of utmost importance. 

  • Stateful inspection firewall: – These firewalls operate at the network layer (Layer 3) and the transport layer (layer 4) of the OSI model. It is an advanced form of firewall that keeps track of the state and context of an active connection. This allows firewalls to make more informed decisions about network traffic enhancing security and providing better protection against threats. When a packet arrives at the firewall it examines the packet headers like a packet filtering firewall (checks for destination and source IP Address) ports and protocol types but unlike traditional packet filtering firewalls, stateful inspection firewalls maintain a state table or stateful connection table. When a packet matches the predefined rules and is permitted the firewalls add an entry to its state table to keep track of the connection, This entry includes detailed information about the connection’s state such as source IP Address, destination IP Address, port numbers, and the current state of the connection (e.g. established, initiated or closed)  
    As more packets were, the firewall compared them with the context provided by the state table and not only to the predefined set of rules. Firewall performs stateful analysis which ensures that incoming packets are part of an established connection. It verifies that it belongs to an active session initiated by an internal host and maintains the state of the connection.  
  • Proxy Firewall: – It operates at the application layer (Layer 7) of the OSI model. They act as intermediaries between the client and the server and handle communication requests on behalf of the originating user. These firewalls provide deep packet inspection by examining the contents of packets and filtering based on application content. They offer a higher level of security. Due to their method of working, they can introduce additional latency.  
     
    Next-Generation Firewalls:- NGFW integrates traditional firewall features with advanced capabilities such as intrusion prevention systems, application awareness, deep packet inspection user and application level controls SSL inspection, and integration with threat intelligence to provide more comprehensive security

Redistribution between OSPF and EIGRP  

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route redistribution between ospf and eigrp
route redistribution between ospf and eigrp

In a network, there is a possibility that it is running on both OSPF and EIGRP and the route of OSPF cannot be advertised to EIGRP by itself. Similarly, routes of EIGRP cannot be advertised to OSPF by itself.   

We can make use of Redistribution to advertise routes between each other. 

Route Redistribution is a process that helps to exchange routing information from one routing protocol to another. It allows routes from one routing protocol to be advertised into another. 

Let us see how we can redistribute routes between OSPF and EIGRP with the help of this basic topology. 

Redistribution between OSPF and EIGRP

Redistribution between OSPF and EIGRP

R1: –  

R1(config)#interface GigabitEthernet0/0/0  

R1(config-if)#ip address 192.168.12.1 255.255.255.0  

R1(config-if)#no shutdown   

R1(config)#interface loopback 1  

R1(config-if)#ip address 1.1.1.1 255.255.255.0  

R1(config-if)#exit   

R1(config)#router ospf 1  

R1(config-router)#network 192.168.12.0 0.0.0.255 area 0  

R1(config-router)#network 1.1.1.0 0.0.0.255 area 0   

R2: –   

R2(config)#interface GigabitEthernet0/0/1  

R2(config-if)#exit  

R2(config)#interface GigabitEthernet0/0/0  

R2(config-if)#ip address 192.168.23.2 255.255.255.0  

R2(config-if)#no shutdown   

R2(config)#interface loopback 1  

R2(config-if)#ip address 2.2.2.1 255.255.255.0   

R2(config)#router eigrp 1  

R2(config-router)#no auto-summary   

R2(config-router)#network 192.168.23.0  

R2(config-router)#network 2.2.2.0  

R2(config-router)#exit  

R2(config)#exit   

R3:-    

R3(config)#interface GigabitEthernet0/0/0  

R3(config-if)#ip address 192.168.12.2 255.255.255.0  

R3(config-if)#no shutdown   

R3(config-if)#exit  

R3(config)#interface GigabitEthernet0/0/1  

R3(config-if)#ip address 192.168.23.3 255.255.255.0  

R3(config-if)#no shutdown    

R3(config)#router ospf 1  

R3(config-router)#network 192.168.12.0 0.0.0.255 area 0  

R3(config-router)#exit   

R3(config)#router eigrp 1  

R3(config-router)#no auto-summary   

R3(config-router)#network 192.168.23.0   

R3(config-router)#exit    

Let us see the table before redistribution.   

R1#show ip route   

Codes:  

L – local, C – connected, S – static, R – RIP, M – mobile, B – BGP  

D – EIGRP, EX – EIGRP external, O – OSPF, IA – OSPF inter area  

N1 – OSPF NSSA external type 1, N2 – OSPF NSSA external type 2  

E1 – OSPF external type 1, E2 – OSPF external type 2, E – EGP  

i – IS-IS, L1 – IS-IS level-1, L2 – IS-IS level-2, ia – IS-IS inter area  

* – candidate default, U – per-user static route, o – ODR  

P – periodic downloaded static route   

Gateway of last resort is not set   

1.0.0.0/8 is variably subnetted, 2 subnets, 2 masks  

C 1.1.1.0/24 is directly connected, Loopback1  

L 1.1.1.1/32 is directly connected, Loopback1  

192.168.12.0/24 is variably subnetted, 2 subnets, 2 masks  

C 192.168.12.0/24 is directly connected, GigabitEthernet0/0/0  

L 192.168.12.1/32 is directly connected, GigabitEthernet0/0/0   

R2#show ip route   

Codes:   

L – local, C – connected, S – static, R – RIP, M – mobile, B – BGP  

 D – EIGRP, EX – EIGRP external, O – OSPF, IA – OSPF inter area  

 N1 – OSPF NSSA external type 1, N2 – OSPF NSSA external type 2  

 E1 – OSPF external type 1, E2 – OSPF external type 2, E – EGP  

 i – IS-IS, L1 – IS-IS level-1, L2 – IS-IS level-2, ia – IS-IS inter area  

 * – candidate default, U – per-user static route, o – ODR  

 P – periodic downloaded static route   

Gateway of last resort is not set   

2.0.0.0/8 is variably subnetted, 2 subnets, 2 masks  

C 2.2.2.0/24 is directly connected, Loopback1  

L 2.2.2.1/32 is directly connected, Loopback1  

192.168.23.0/24 is variably subnetted, 2 subnets, 2 masks  

C 192.168.23.0/24 is directly connected, GigabitEthernet0/0/0  

L 192.168.23.2/32 is directly connected, GigabitEthernet0/0/0   

R3#show ip route   

Codes:  

L – local, C – connected, S – static, R – RIP, M – mobile, B – BGP  

D – EIGRP, EX – EIGRP external, O – OSPF, IA – OSPF inter area  

N1 – OSPF NSSA external type 1, N2 – OSPF NSSA external type 2  

E1 – OSPF external type 1, E2 – OSPF external type 2, E – EGP  

i – IS-IS, L1 – IS-IS level-1, L2 – IS-IS level-2, ia – IS-IS inter area  

* – candidate default, U – per-user static route, o – ODR  

P – periodic downloaded static route   

Gateway of last resort is not set    

1.0.0.0/32 is subnetted, 1 subnets  

O 1.1.1.1/32 [110/2] via 192.168.12.1, 00:02:27, GigabitEthernet0/0/0  

2.0.0.0/24 is subnetted, 1 subnets  

D 2.2.2.0/24 [90/130816] via 192.168.23.2, 00:00:37, GigabitEthernet0/0/1  

192.168.12.0/24 is variably subnetted, 2 subnets, 2 masks  

C 192.168.12.0/24 is directly connected, GigabitEthernet0/0/0  

L 192.168.12.2/32 is directly connected, GigabitEthernet0/0/0  

192.168.23.0/24 is variably subnetted, 2 subnets, 2 masks  

C 192.168.23.0/24 is directly connected, GigabitEthernet0/0/1  

L 192.168.23.3/32 is directly connected, GigabitEthernet0/0/1  

Redistribution: -

R3#configure t  

R3(config)#router eigrp 1  

R3(config-router)#redistribute ospf ?  

<1-65535> Process ID   

R3(config-router)#redistribute ospf 1 ?   

match Redistribution of OSPF routes  

metric Metric for redistributed routes  

<cr>   

R3(config-router)#redistribute ospf 1 metric ?   

<1-4294967295> Bandwidth metric in Kbits per second   

R3(config-router)#redistribute ospf 1 metric 1000 ?   

<0-4294967295> EIGRP delay metric, in 10 microsecond units   

R3(config-router)#redistribute ospf 1 metric 1000 100 ?   

<0-255> EIGRP reliability metric where 255 is 100% reliable   

R3(config-router)#redistribute ospf 1 metric 1000 100 255 ?   

<1-255> EIGRP Effective bandwidth metric (Loading) where 255 is 100% loaded   

R3(config-router)#redistribute ospf 1 metric 1000 100 255 ?   

<1-255> EIGRP Effective bandwidth metric (Loading) where 255 is 100% loaded   

R3(config-router)#redistribute ospf 1 metric 1000 100 255 1 ?   

<1-65535> EIGRP MTU of the path   

R3(config-router)#redistribute ospf 1 metric 1000 100 255 1 1500  

R3(config-router)#exit   

R3(config)#router ospf 1   

R3(config-router)#redistribute eigrp ?   

<1-65535> Autonomous system number   

R3(config-router)#redistribute eigrp 1   

% Only classful networks will be redistributed   

R3(config-router)#redistribute eigrp 1 ?   

metric Metric for redistributed routes  

metric-type OSPF/IS-IS exterior metric type for redistributed routes  

subnets Consider subnets for redistribution into OSPF  

tag Set tag for routes redistributed into OSPF  

<cr>   

R3(config-router)#redistribute eigrp 1 subnets ?   

tag Set tag for routes redistributed into OSPF  

<cr>   

R3(config-router)#redistribute eigrp 1 subnets 

Verification: -

R1>show ip route   

Codes:  

L – local, C – connected, S – static, R – RIP, M – mobile, B – BGP  

D – EIGRP, EX – EIGRP external, O – OSPF, IA – OSPF inter area  

N1 – OSPF NSSA external type 1, N2 – OSPF NSSA external type 2  

E1 – OSPF external type 1, E2 – OSPF external type 2, E – EGP  

i – IS-IS, L1 – IS-IS level-1, L2 – IS-IS level-2, ia – IS-IS inter area  

* – candidate default, U – per-user static route, o – ODR  

P – periodic downloaded static route  

Gateway of last resort is not set

 1.0.0.0/8 is variably subnetted, 2 subnets, 2 masks  

C 1.1.1.0/24 is directly connected, Loopback1  

L 1.1.1.1/32 is directly connected, Loopback1  

 2.0.0.0/24 is subnetted, 1 subnets  

O E2 2.2.2.0/24 [110/20] via 192.168.12.2, 00:00:27, GigabitEthernet0/0/0  

192.168.12.0/24 is variably subnetted, 2 subnets, 2 masks  

C 192.168.12.0/24 is directly connected, GigabitEthernet0/0/0  

L 192.168.12.1/32 is directly connected, GigabitEthernet0/0/0  

O E2 192.168.23.0/24 [110/20] via 192.168.12.2, 00:00:46, GigabitEthernet0/0/0  

R2#show ip route   

Codes:  

L – local, C – connected, S – static, R – RIP, M – mobile, B – BGP  

D – EIGRP, EX – EIGRP external, O – OSPF, IA – OSPF inter area  

N1 – OSPF NSSA external type 1, N2 – OSPF NSSA external type 2  

E1 – OSPF external type 1, E2 – OSPF external type 2, E – EGP  

i – IS-IS, L1 – IS-IS level-1, L2 – IS-IS level-2, ia – IS-IS inter area  

* – candidate default, U – per-user static route, o – ODR  

P – periodic downloaded static route  

Gateway of last resort is not set  

 1.0.0.0/32 is subnetted, 1 subnets  

D EX 1.1.1.1/32 [170/2585856] via 192.168.23.3, 00:01:40, GigabitEthernet0/0/0  

 2.0.0.0/8 is variably subnetted, 2 subnets, 2 masks  

C 2.2.2.0/24 is directly connected, Loopback1  

L 2.2.2.1/32 is directly connected, Loopback1  

D EX 192.168.12.0/24 [170/2585856] via 192.168.23.3, 00:01:40, GigabitEthernet0/0/0  

192.168.23.0/24 is variably subnetted, 2 subnets, 2 masks  

C 192.168.23.0/24 is directly connected, GigabitEthernet0/0/0  

L 192.168.23.2/32 is directly connected, GigabitEthernet0/0/0  

R3#show ip route   

Codes:  

L – local, C – connected, S – static, R – RIP, M – mobile, B BGP  

D – EIGRP, EX – EIGRP external, O – OSPF, IA – OSPF inter area  

N1 – OSPF NSSA external type 1, N2 – OSPF NSSA external type 2  

E1 – OSPF external type 1, E2 – OSPF external type 2, E – EGP  

i – IS-IS, L1 – IS-IS level-1, L2 – IS-IS level-2, ia – IS-IS inter area  

* – candidate default, U – per-user static route, o – ODR  

P – periodic downloaded static route  

Gateway of last resort is not set  

1.0.0.0/32 is subnetted, 1 subnets  

O 1.1.1.1/32 [110/2] via 192.168.12.1, 00:12:55, GigabitEthernet0/0/0  

2.0.0.0/24 is subnetted, 1 subnets  

D 2.2.2.0/24 [90/130816] via 192.168.23.2, 00:11:05, GigabitEthernet0/0/1  

192.168.12.0/24 is variably subnetted, 2 subnets, 2 masks  

C 192.168.12.0/24 is directly connected, GigabitEthernet0/0/0  

L 192.168.12.2/32 is directly connected, GigabitEthernet0/0/0  

192.168.23.0/24 is variably subnetted, 2 subnets, 2 masks  

C 192.168.23.0/24 is directly connected, GigabitEthernet0/0/1  

L 192.168.23.3/32 is directly connected, GigabitEthernet0/0/1 

Redistribution Between RIP and OSPF 

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Redistribution Between RIP and OSPF
Redistribution Between RIP and OSPF

In a network, there is a possibility that it is running on both OSPF and RIP and the route of OSPF cannot be advertised to RIP by itself. Similarly, routes of RIP cannot be advertised to OSPF by itself.  

Now the question arises how can R2 reach the routes advertised on R1?  

We can also consider this as how can routes of OSPF and RIP reach each other.  

Guessed right, we can make use of Redistribution to advertise routes between each other.  

Route Redistribution is a process that helps to exchange routing information from one routing protocol to another. It allows routes from one routing protocol to be advertised into another.    

Let us now see the configuration to redistribute routes between RIP and OSPF. 

configuration to redistribute routes between RIP and OSPF

R1: –  

R1(config)#interface GigabitEthernet0/0/0  

R1(config-if)#ip address 192.168.12.1 255.255.255.0  

R1(config-if)#no shutdown   

R1(config-if)#exit  

R1(config)#interface loopback 1  

R1(config-if)#ip address 1.1.1.1 255.255.255.0  

R1(config-if)#exit  

R1(config)#router ospf 1  

R1(config-router)#network 1.1.1.0 0.0.0.255 area 0  

R1(config-router)#network 192.168.12.0 0.0.0.255 area 0  

R2: –  

R2(config)#interface GigabitEthernet0/0/0  

R2(config-if)#ip address 192.168.23.1 255.255.255.0  

R2(config-if)#no shutdown   

R2(config)#interface loopback 1  

R2(config-if)#ip address 2.2.2.1 255.255.255.0  

R2(config-if)#exit  

R2(config)#router rip   

R2(config-router)#version 2  

R2(config-router)#no auto-summary   

R2(config-router)#network 192.168.23.0  

R2(config-router)#network 2.2.2.0  

R2(config-router)#exit  

R3: –  

R3(config)#interface GigabitEthernet0/0/0  

R3(config-if)#ip address 192.168.12.2 255.255.255.0  

R3(config-if)#no shutdown   

R3(config-if)#exit  

R3(config)#interface GigabitEthernet0/0/1  

R3(config-if)#ip address 192.168.23.2 255.255.255.0  

R3(config-if)#no shutdown   

R3(config)#router ospf 1  

R3(config-router)#network 192.168.12.0 0.0.0.255 area 0  

R3(config-router)#exit  

R3(config)#router rip  

R3(config-router)#version 2  

R3(config-router)#no auto-summary   

R3(config-router)#network 192.168.23.0  

R3(config-router)#exit  

Let us check the routes before redistribution.  

R1#show ip route   

Codes:   

L – local, C – connected, S – static, R – RIP, M – mobile, B – BGP  

D – EIGRP, EX – EIGRP external, O – OSPF, IA – OSPF inter area  

N1 – OSPF NSSA external type 1, N2 – OSPF NSSA external type 2  

E1 – OSPF external type 1, E2 – OSPF external type 2, E – EGP  

i – IS-IS, L1 – IS-IS level-1, L2 – IS-IS level-2, ia – IS-IS inter area  

* – candidate default, U – per-user static route, o – ODR  

P – periodic downloaded static route  

Gateway of last resort is not set  

1.0.0.0/8 is variably subnetted, 2 subnets, 2 masks  

C 1.1.1.0/24 is directly connected, Loopback1  

L 1.1.1.1/32 is directly connected, Loopback1  

192.168.12.0/24 is variably subnetted, 2 subnets, 2 masks  

C 192.168.12.0/24 is directly connected, GigabitEthernet0/0/0  

L 192.168.12.1/32 is directly connected, GigabitEthernet0/0/0  

R2>show ip route   

Codes:   

L – local, C – connected, S – static, R – RIP, M – mobile, B – BGP  

D – EIGRP, EX – EIGRP external, O – OSPF, IA – OSPF inter area  

N1 – OSPF NSSA external type 1, N2 – OSPF NSSA external type 2  

E1 – OSPF external type 1, E2 – OSPF external type 2, E – EGP  

i – IS-IS, L1 – IS-IS level-1, L2 – IS-IS level-2, ia – IS-IS inter area  

* – candidate default, U – per-user static route, o – ODR  

P – periodic downloaded static route  

Gateway of last resort is not set  

2.0.0.0/8 is variably subnetted, 2 subnets, 2 masks  

C 2.2.2.0/24 is directly connected, Loopback1  

L 2.2.2.1/32 is directly connected, Loopback1  

 192.168.23.0/24 is variably subnetted, 2 subnets, 2 masks  

C 192.168.23.0/24 is directly connected, GigabitEthernet0/0/0  

L 192.168.23.1/32 is directly connected, GigabitEthernet0/0/0  

R3#show ip route   

Codes:  

L – local, C – connected, S – static, R – RIP, M – mobile, B – BGP  

D – EIGRP, EX – EIGRP external, O – OSPF, IA – OSPF inter area  

N1 – OSPF NSSA external type 1, N2 – OSPF NSSA external type 2  

E1 – OSPF external type 1, E2 – OSPF external type 2, E – EGP  

i – IS-IS, L1 – IS-IS level-1, L2 – IS-IS level-2, ia – IS-IS inter area  

* – candidate default, U – per-user static route, o – ODR  

P – periodic downloaded static route  

Gateway of last resort is not set  

1.0.0.0/32 is subnetted, 1 subnets  

O 1.1.1.1/32 [110/2] via 192.168.12.1, 00:04:56, GigabitEthernet0/0/0  

 2.0.0.0/24 is subnetted, 1 subnets  

R 2.2.2.0/24 [120/1] via 192.168.23.1, 00:00:07, GigabitEthernet0/0/1  

 192.168.12.0/24 is variably subnetted, 2 subnets, 2 masks  

C 192.168.12.0/24 is directly connected, GigabitEthernet0/0/0  

L 192.168.12.2/32 is directly connected, GigabitEthernet0/0/0  

 192.168.23.0/24 is variably subnetted, 2 subnets, 2 masks  

C 192.168.23.0/24 is directly connected, GigabitEthernet0/0/1  

L 192.168.23.2/32 is directly connected, GigabitEthernet0/0/1  

REDISTRIBUTION:-

R3(config)#router rip  

R3(config-router)#redistribute ospf ?   

<1-65535> Process ID   

R3(config-router)#redistribute ospf 1 ?   

match Redistribution of OSPF routes   

metric Metric for redistributed routes  

<cr>  

R3(config-router)#redistribute ospf 1 metric ?   

<0-16> Default metric  

transparent Transparently redistribute metric  

R3(config-router)#redistribute ospf 1 metric 5 ?   

match Redistribution of OSPF routes  

<cr>  

R3(config-router)#redistribute ospf 1 metric 5   

R3(config-router)#exit  

R3(config)#router ospf 1  

R3(config-router)#redistribute rip  

R3(config-router)#redistribute rip subnets ?  

tag Set tag for routes redistributed into OSPF  

<cr>  

R3(config-router)#redistribute rip subnets   

R3(config-router)#exit  

R3#show ip route   

Codes:   

L – local, C – connected, S – static, R – RIP, M – mobile, B – BGP  

 D – EIGRP, EX – EIGRP external, O – OSPF, IA – OSPF inter area  

 N1 – OSPF NSSA external type 1, N2 – OSPF NSSA external type 2  

 E1 – OSPF external type 1, E2 – OSPF external type 2, E – EGP  

 i – IS-IS, L1 – IS-IS level-1, L2 – IS-IS level-2, ia – IS-IS inter area  

 * – candidate default, U – per-user static route, o – ODR  

 P – periodic downloaded static route   

Gateway of last resort is not set   

 1.0.0.0/32 is subnetted, 1 subnets  

O 1.1.1.1/32 [110/2] via 192.168.12.1, 00:08:51, GigabitEthernet0/0/0  

 2.0.0.0/24 is subnetted, 1 subnets  

R 2.2.2.0/24 [120/1] via 192.168.23.1, 00:00:21, GigabitEthernet0/0/1  

 192.168.12.0/24 is variably subnetted, 2 subnets, 2 masks  

C 192.168.12.0/24 is directly connected, GigabitEthernet0/0/0  

L 192.168.12.2/32 is directly connected, GigabitEthernet0/0/0  

 192.168.23.0/24 is variably subnetted, 2 subnets, 2 masks  

C 192.168.23.0/24 is directly connected, GigabitEthernet0/0/1  

L 192.168.23.2/32 is directly connected, GigabitEthernet0/0/1  

VERIFICATION:-

R1#show ip route   

Codes:   

L – local, C – connected, S – static, R – RIP, M – mobile, B – BGP  

 D – EIGRP, EX – EIGRP external, O – OSPF, IA – OSPF inter area  

 N1 – OSPF NSSA external type 1, N2 – OSPF NSSA external type 2  

 E1 – OSPF external type 1, E2 – OSPF external type 2, E – EGP  

 i – IS-IS, L1 – IS-IS level-1, L2 – IS-IS level-2, ia – IS-IS inter area  

 * – candidate default, U – per-user static route, o – ODR  

 P – periodic downloaded static route  

Gateway of last resort is not set  

 1.0.0.0/8 is variably subnetted, 2 subnets, 2 masks  

C 1.1.1.0/24 is directly connected, Loopback1  

L 1.1.1.1/32 is directly connected, Loopback1  

 2.0.0.0/24 is subnetted, 1 subnets  

O E2 2.2.2.0/24 [110/20] via 192.168.12.2, 00:00:29, GigabitEthernet0/0/0  

 192.168.12.0/24 is variably subnetted, 2 subnets, 2 masks  

C 192.168.12.0/24 is directly connected, GigabitEthernet0/0/0  

L 192.168.12.1/32 is directly connected, GigabitEthernet0/0/0  

O E2 192.168.23.0/24 [110/20] via 192.168.12.2, 00:00:29, GigabitEthernet0/0/0  

R2>show ip route   

Codes:   

L – local, C – connected, S – static, R – RIP, M – mobile, B – BGP  

D – EIGRP, EX – EIGRP external, O – OSPF, IA – OSPF inter area  

N1 – OSPF NSSA external type 1, N2 – OSPF NSSA external type 2  

E1 – OSPF external type 1, E2 – OSPF external type 2, E – EGP  

i – IS-IS, L1 – IS-IS level-1, L2 – IS-IS level-2, ia – IS-IS inter area  

* – candidate default, U – per-user static route, o – ODR  

P – periodic downloaded static route  

Gateway of last resort is not set  

1.0.0.0/32 is subnetted, 1 subnets  

R 1.1.1.1/32 [120/5] via 192.168.23.2, 00:00:07, GigabitEthernet0/0/0  

2.0.0.0/8 is variably subnetted, 2 subnets, 2 masks  

C 2.2.2.0/24 is directly connected, Loopback1  

L 2.2.2.1/32 is directly connected, Loopback1  

R 192.168.12.0/24 [120/5] via 192.168.23.2, 00:00:07, GigabitEthernet0/0/0  

192.168.23.0/24 is variably subnetted, 2 subnets, 2 masks  

C 192.168.23.0/24 is directly connected, GigabitEthernet0/0/0  

L 192.168.23.1/32 is directly connected, GigabitEthernet0/0/0  

R3#show ip route   

Codes:  

L – local, C – connected, S – static, R – RIP, M – mobile, B – BGP  

D – EIGRP, EX – EIGRP external, O – OSPF, IA – OSPF inter area  

N1 – OSPF NSSA external type 1, N2 – OSPF NSSA external type 2  

E1 – OSPF external type 1, E2 – OSPF external type 2, E – EGP  

i – IS-IS, L1 – IS-IS level-1, L2 – IS-IS level-2, ia – IS-IS inter area  

* – candidate default, U – per-user static route, o – ODR  

P – periodic downloaded static route  

Gateway of last resort is not set  

 1.0.0.0/32 is subnetted, 1 subnets  

O 1.1.1.1/32 [110/2] via 192.168.12.1, 00:12:21, GigabitEthernet0/0/0  

 2.0.0.0/24 is subnetted, 1 subnets  

R 2.2.2.0/24 [120/1] via 192.168.23.1, 00:00:08, GigabitEthernet0/0/1  

 192.168.12.0/24 is variably subnetted, 2 subnets, 2 masks  

C 192.168.12.0/24 is directly connected, GigabitEthernet0/0/0  

L 192.168.12.2/32 is directly connected, GigabitEthernet0/0/0  

 192.168.23.0/24 is variably subnetted, 2 subnets, 2 masks  

C 192.168.23.0/24 is directly connected, GigabitEthernet0/0/1  

L 192.168.23.2/32 is directly connected, GigabitEthernet0/0/1 

Route Redistribution: Explained in Detail

by
cisco route redistribution
cisco route redistribution

Routing protocols are used to exchange routing information and select the best routes. But what if a network is configured with 2 or more different routing protocols? Do they share the routes between them?

What is Route Redistribution?

Route Redistribution is a process that helps to exchange routing information from one routing protocol to another. It allows routes from one routing protocol to be advertised into another routing protocol. Since routes are advertised between all the routing protocols, routers can make routing decisions based on the combined information.

The receiving routing protocol considers the redistributed routes as an external route.

External routes are preferred less compared to locally originated routes.
Route redistribution enables the exchange of routing information between different routing protocols, such as OSPF, EIGRP, BGP, and RIP. It can also be used to redistribute static or directly connected routes.

Route Redistribution generally requires at least one redistribution point. i.e., the router/device should run both routing protocols. See Fig: –

In our given example, Router B requires to have at least one interface configured with EIGRP and at least one interface configured with OSPF.
In some cases, a network is configured with the same routing protocol

Let’s take an example to understand the configuration.

Redistribution between RIP and EIGRP

Redistribution between RIP and EIGRP

Configuring Routing Protocols:- 

 

R1:-  

 

R1(config)#interface GigabitEthernet0/0/0 

R1(config-if)#ip address 192.168.12.1 

R1(config-if)#ip address 192.168.12.1 255.255.255.0 

R1(config-if)#no shutdown  

R1(config-if)#exit 

R1(config)#interface loopback 1 

R1(config-if)#ip address 1.1.1.1 255.255.255.0 

R1(config-if)#exit 

 

R1(config)#router eigrp 1 

R1(config-router)#no auto-summary  

R1(config-router)#network 192.168.12.0 

R1(config-router)#network 1.1.1.0 

 

R2:- 

 

R2(config)#interface GigabitEthernet0/0/0 

R2(config-if)#ip address 192.168.23.1 255.255.255.0 

R2(config-if)#no shutdown  

R2(config-if)#exit 

R2(config)#interface loopback 1 

R2(config-if)#ip address 2.2.2.1 255.255.255.0 

 

R2(config)#router rip 

R2(config-router)#version 2 

R2(config-router)#no auto-summary  

R2(config-router)#network 192.168.23.0 

R2(config-router)#network 2.2.2.0 

R2(config-router)#exit 

 

R3: – 

 

Router(config)#hostname R3 

R3(config)#interface GigabitEthernet0/0/0 

R3(config-if)#ip address 192.168.12.2 255.255.255.0 

R3(config-if)#no shutdown  

 

R3(config)#interface GigabitEthernet0/0/1 

R3(config-if)#ip add 

R3(config-if)#ip address 192.168.23.2 255.255.255.0 

R3(config-if)#no shutdown  

R3(config)#interface lo 

R3(config)#interface loopback 1 

 

R3(config-router)#router eigrp 1 

R3(config-router)#no auto-summary  

R3(config-router)#network 192.168.12.0 

 

R3(config-router)#exit 

R3(config-router)#version 2 

R3(config-router)#no auto-summary  

R3(config-router)#network 192.168.23.0 

 

Verification: – 

 

R1#show ip route  

Codes: L – local, C – connected, S – static, R – RIP, M – mobile, B – BGP 

 D – EIGRP, EX – EIGRP external, O – OSPF, IA – OSPF inter area 

 N1 – OSPF NSSA external type 1, N2 – OSPF NSSA external type 2 

 E1 – OSPF external type 1, E2 – OSPF external type 2, E – EGP 

 i – IS-IS, L1 – IS-IS level-1, L2 – IS-IS level-2, ia – IS-IS inter area 

 * – candidate default, U – per-user static route, o – ODR 

 P – periodic downloaded static route 

 

The Gateway of last resort is not set 

 

1.0.0.0/8 is variably subnetted, 2 subnets, 2 masks 

C 1.1.1.0/24 is directly connected, Loopback1 

L 1.1.1.1/32 is directly connected, Loopback1 

192.168.12.0/24 is variably subnetted, 2 subnets, 2 masks 

C 192.168.12.0/24 is directly connected, GigabitEthernet0/0/0 

L 192.168.12.1/32 is directly connected, GigabitEthernet0/0/0 

 

R2#show ip route  

Codes: L – local, C – connected, S – static, R – RIP, M – mobile, B – BGP 

 D – EIGRP, EX – EIGRP external, O – OSPF, IA – OSPF inter area 

 N1 – OSPF NSSA external type 1, N2 – OSPF NSSA external type 2 

 E1 – OSPF external type 1, E2 – OSPF external type 2, E – EGP 

 i – IS-IS, L1 – IS-IS level-1, L2 – IS-IS level-2, ia – IS-IS inter area 

 * – candidate default, U – per-user static route, o – ODR 

 P – periodic downloaded static route 

 

The Gateway of last resort is not set 

 

 2.0.0.0/8 is variably subnetted, 2 subnets, 2 masks 

C 2.2.2.0/24 is directly connected, Loopback1 

L 2.2.2.1/32 is directly connected, Loopback1 

 192.168.23.0/24 is variably subnetted, 2 subnets, 2 masks 

C 192.168.23.0/24 is directly connected, GigabitEthernet0/0/0 

L 192.168.23.1/32 is directly connected, GigabitEthernet0/0/0 

 

R3>show ip route  

Codes: L – local, C – connected, S – static, R – RIP, M – mobile, B – BGP 

 D – EIGRP, EX – EIGRP external, O – OSPF, IA – OSPF inter area 

 N1 – OSPF NSSA external type 1, N2 – OSPF NSSA external type 2 

 E1 – OSPF external type 1, E2 – OSPF external type 2, E – EGP 

 i – IS-IS, L1 – IS-IS level-1, L2 – IS-IS level-2, ia – IS-IS inter area 

 * – candidate default, U – per-user static route, o – ODR 

 P – periodic downloaded static route 

 

The Gateway of last resort is not set 

 

 1.0.0.0/24 is subnetted, 1 subnets 

D 1.1.1.0/24 [90/130816] via 192.168.12.1, 00:11:17, GigabitEthernet0/0/0 

 2.0.0.0/24 is subnetted, 1 subnets 

R 2.2.2.0/24 [120/1] via 192.168.23.1, 00:00:22, GigabitEthernet0/0/1 

 192.168.12.0/24 is variably subnetted, 2 subnets, 2 masks 

C 192.168.12.0/24 is directly connected, GigabitEthernet0/0/0 

L 192.168.12.2/32 is directly connected, GigabitEthernet0/0/0 

 192.168.23.0/24 is variably subnetted, 2 subnets, 2 masks 

C 192.168.23.0/24 is directly connected, GigabitEthernet0/0/1 

L 192.168.23.2/32 is directly connected, GigabitEthernet0/0/1 

 

Redistribution: – 

 

R3(config)#router rip 

R3(config-router)#redistribute eigrp 1 

 

R3(config-router)#redistribute eigrp 1 ? 

 

metric Metric for redistributed routes 

 

R3(config-router)#redistribute eigrp 1 metric 5 

R3(config-router)#exit 

 

R3(config)#router eigrp 1 

R3(config-router)#redistribute rip metric ?                    

 

 (We can configure different metrics in it) 

 

<1-4294967295> Bandwidth metric in Kbits per second 

 

R3(config-router)#redistribute rip metric 1000 ? 

 

<0-4294967295> EIGRP delay metric, in 10 microsecond units 

 

R3(config-router)#redistribute rip metric 1000 100 ? 

 

<0-255> EIGRP reliability metric where 255 is 100% reliable 

 

R3(config-router)#redistribute rip metric 1000 100 255 ? 

 

<1-255> EIGRP Effective bandwidth metric (Loading) where 255 is 100% loaded 

 

R3(config-router)#redistribute rip metric 1000 100 255 1 ? 

 

<1-65535> EIGRP MTU of the path 

 

R3(config-router)#redistribute rip metric 1000 100 255 1 1500  

R3(config-router)#exit 

 

Verification: – 

We can now see redistributed routes also. 

 

R3#show ip route  

Codes: L – local, C – connected, S – static, R – RIP, M – mobile, B – BGP 

D – EIGRP, EX – EIGRP external, O – OSPF, IA – OSPF inter area 

N1 – OSPF NSSA external type 1, N2 – OSPF NSSA external type 2 

E1 – OSPF external type 1, E2 – OSPF external type 2, E – EGP 

i – IS-IS, L1 – IS-IS level-1, L2 – IS-IS level-2, ia – IS-IS inter area 

* – candidate default, U – per-user static route, o – ODR 

P – periodic downloaded static route 

 

The Gateway of last resort is not set 

 

D 1.0.0.0/8 [90/130816] via 192.168.12.1, 00:15:55, GigabitEthernet0/0/0 

2.0.0.0/24 is subnetted, 1 subnets 

R 2.2.2.0/24 [120/1] via 192.168.23.1, 00:00:04, GigabitEthernet0/0/1 

192.168.12.0/24 is variably subnetted, 2 subnets, 2 masks 

C 192.168.12.0/24 is directly connected, GigabitEthernet0/0/0 

L 192.168.12.2/32 is directly connected, GigabitEthernet0/0/0 

192.168.23.0/24 is variably subnetted, 2 subnets, 2 masks 

C 192.168.23.0/24 is directly connected, GigabitEthernet0/0/1 

L 192.168.23.2/32 is directly connected, GigabitEthernet0/0/1 

 

R1>show ip route  

Codes: L – local, C – connected, S – static, R – RIP, M – mobile, B – BGP 

 D – EIGRP, EX – EIGRP external, O – OSPF, IA – OSPF inter area 

 N1 – OSPF NSSA external type 1, N2 – OSPF NSSA external type 2 

 E1 – OSPF external type 1, E2 – OSPF external type 2, E – EGP 

 i – IS-IS, L1 – IS-IS level-1, L2 – IS-IS level-2, ia – IS-IS inter area 

 * – candidate default, U – per-user static route, o – ODR 

 P – periodic downloaded static route 

 

The Gateway of last resort is not set 

 

1.0.0.0/8 is variably subnetted, 3 subnets, 3 masks 

D 1.0.0.0/8 is a summary, 00:16:17, Null0 

C 1.1.1.0/24 is directly connected, Loopback1 

L 1.1.1.1/32 is directly connected, Loopback1 

 2.0.0.0/24 is subnetted, 1 subnets 

D EX 2.2.2.0/24 [170/2585856] via 192.168.12.2, 00:00:55, GigabitEthernet0/0/0 

 192.168.12.0/24 is variably subnetted, 2 subnets, 2 masks 

C 192.168.12.0/24 is directly connected, GigabitEthernet0/0/0 

L 192.168.12.1/32 is directly connected, GigabitEthernet0/0/0 

D EX 192.168.23.0/24 [170/2585856] via 192.168.12.2, 00:00:55, GigabitEthernet0/0/0 

 

R2>show ip route  

Codes: L – local, C – connected, S – static, R – RIP, M – mobile, B – BGP 

 D – EIGRP, EX – EIGRP external, O – OSPF, IA – OSPF inter area 

 N1 – OSPF NSSA external type 1, N2 – OSPF NSSA external type 2 

 E1 – OSPF external type 1, E2 – OSPF external type 2, E – EGP 

 i – IS-IS, L1 – IS-IS level-1, L2 – IS-IS level-2, ia – IS-IS inter area 

 * – candidate default, U – per-user static route, o – ODR 

 P – periodic downloaded static route 

 

The Gateway of last resort is not set 

 

R 1.0.0.0/8 [120/5] via 192.168.23.2, 00:00:08, GigabitEthernet0/0/0 

 2.0.0.0/8 is variably subnetted, 2 subnets, 2 masks 

C 2.2.2.0/24 is directly connected, Loopback1 

L 2.2.2.1/32 is directly connected, Loopback1 

R 192.168.12.0/24 [120/5] via 192.168.23.2, 00:00:08, GigabitEthernet0/0/0 

 192.168.23.0/24 is variably subnetted, 2 subnets, 2 masks 

C 192.168.23.0/24 is directly connected, GigabitEthernet0/0/0 

L 192.168.23.1/32 is directly connected, GigabitEthernet0/0/0

What is Route Summarization?: Explained

by
route summarization
route summarization

Route summarization, also known as route aggregation or supernetting, is a technique used in networking to reduce the number of routes in a routing table by combining multiple smaller subnets into a single larger network address. Route Summarization helps simplify and optimize routing in a network. It can be used in routing protocols like OSPF, EIGRP, and BGP.

What are the advantages of Route Summarization?

The advantages of Route Summarization are as follows-

  • The key benefit of route summarization is a smaller routing table. Since with the help of summarization, multiple routes are aggregated into a single summarized route, routing table size decreases. 
  • Summarization helps in saving bandwidth. Since the routing table is reduced, less information must be exchanged between routers during the routing protocol updates. This leads to more efficient use of network bandwidth and faster convergence in response to network changes 
  • Route Summarization also helps to save CPU memory and less processing since routes are fewer and hence fewer packets to process. 

How to summarize routes?

  • First, list all the subnets you want to summarize. These subnets should be contiguous. 

Let’s take  

  1. 172.16.0.0/24 
  2. 172.16.1.0/24 
  • Convert the subnets to binary form.  

172.16.0.1/24: – 10101100000100000000000000000001 

172.16.1.1/24: – 10101100000100000000000100000001 

  • Calculate the number of common bits in this binary format. 

10101100000100000000000000000001 

10101100000100000000000100000001 

Here we have 23 bits in common. 

Hence our summary address subnet mask will be /23 and the summary address will be 172.16.0.0/23 

Configuration: – 

Let us look at the configuration of Summarization using the topology below. 

EIGRP configuration

Router#configure terminal  

Router(config)#hostname R1 

R1(config)#interface fastEthernet 0/0 

R1(config-if)#ip address 192.168.12.1 255.255.255.0 

R1(config-if)#no shutdown  

R1(config-if)#exit 

R1(config)#interface loopback 0 

R1(config-if)#ip address 172.16.0.1 255.255.255.0 

R1(config-if)#exit 

R1(config)#interface loopback 1 

R1(config-if)#ip address 172.16.1.1 255.255.255.0 

R1(config-if)#exit 

 

EIGRP CONFIGURATION: – 

 

R1(config)#router eigrp 1 

R1(config-router)#no auto-summary  

R1(config-router)#network 192.168.12.0 

R1(config-router)#network 172.16.0.0 

R1(config-router)#exit 

 

R2: – 

 

Router#configure terminal  

Router(config)#hostname R2 

R2(config)#interface fastEthernet 0/1 

R2(config-if)#ip address 192.168.12.2 255.255.255.0 

R2(config-if)#no shutdown  

R2(config-if)#exit 

 

EIGRP CONFIGURATION: – 

 

R2(config)#router eigrp 1 

R2(config-router)#no auto-summary  

R2(config-router)#network 192.168.12.0 

 

*Mar 1 00:05:27.191: %DUAL-5-NBRCHANGE: IP-EIGRP(0) 1: Neighbor 192.168.12.1  

(FastEthernet0/1) is up: new adjacency 

 

EIGRP is UP.  

 

Verification: –  

 

Let us check the routes on R1 and R2 

 

R1#show ip route  

Codes: C – connected, S – static, R – RIP, M – mobile, B – BGP 

       D – EIGRP, EX – EIGRP external, O – OSPF, IA – OSPF inter area  

       N1 – OSPF NSSA external type 1, N2 – OSPF NSSA external type 2 

       E1 – OSPF external type 1, E2 – OSPF external type 2 

       i – IS-IS, su – IS-IS summary, L1 – IS-IS level-1, L2 – IS-IS level-2 

       ia – IS-IS inter area, * – candidate default, U – per-user static route 

       o – ODR, P – periodic downloaded static route 

 

The Gateway of last resort is not set 

 

C 192.168.12.0/24 is directly connected, FastEthernet0/0 

     172.16.0.0/24 is subnetted, 2 subnets 

C 172.16.0.0 is directly connected, Loopback0 

C 172.16.1.0 is directly connected, Loopback1 

 

R2#show ip route eigrp  

     172.16.0.0/24 is subnetted, 2 subnets 

D 172.16.0.0 [90/409600] via 192.168.12.1, 00:01:47, FastEthernet0/1 

D 172.16.1.0 [90/409600] via 192.168.12.1, 00:01:47, FastEthernet0/1 

 

R2#show ip route  

Codes: C – connected, S – static, R – RIP, M – mobile, B – BGP 

       D – EIGRP, EX – EIGRP external, O – OSPF, IA – OSPF inter area  

       N1 – OSPF NSSA external type 1, N2 – OSPF NSSA external type 2 

       E1 – OSPF external type 1, E2 – OSPF external type 2 

       i – IS-IS, su – IS-IS summary, L1 – IS-IS level-1, L2 – IS-IS level-2 

       ia – IS-IS inter area, * – candidate default, U – per-user static route 

       o – ODR, P – periodic downloaded static route 

 

The Gateway of last resort is not set 

 

C 192.168.12.0/24 is directly connected, FastEthernet0/1 

     172.16.0.0/24 is subnetted, 2 subnets 

D 172.16.0.0 [90/409600] via 192.168.12.1, 00:02:57, FastEthernet0/1 

D 172.16.1.0 [90/409600] via 192.168.12.1, 00:02:57, FastEthernet0/1 

 

R2#ping 172.16.0.1 

 

Type escape sequence to abort. 

Sending 5, 100-byte ICMP Echos to 172.16.0.1, timeout is 2 seconds: 

!!!!! 

Success rate is 100 percent (5/5), round-trip min/avg/max = 8/12/20 ms 

 

We can ping 172.16.0.1 hence it is reachable. 

 

Summarization: – 

 

Since we have already calculated the summarized network for 172.16.0.0/24, 172.16.1.0/24 which is 172.16.0.0/23. Let’s configure it. 

 

R1#configure terminal  

R1(config)#interface fastEthernet 0/0  

R1(config-if)#ip summary-address eigrp 1 172.16.0.0 255.255.254.0 

 

*Mar 1 00:09:54.743: %DUAL-5-NBRCHANGE: IP-EIGRP(0) 1: Neighbor 192.168.12.2  

(FastEthernet0/0) is resync: summary configured 

EIGRP configuration

The above message pops up which shows that summarization is configured. 

 

R2: – 

 

*Mar 1 00:09:32.251: %DUAL-5-NBRCHANGE: IP-EIGRP(0) 1: Neighbor 192.168.12.1  

(FastEthernet0/1) is resync: peer graceful-restart 

EIGRP configuration

The above message pops up which shows that summarization is configured. 

 

R2: – 

 

*Mar 1 00:09:32.251: %DUAL-5-NBRCHANGE: IP-EIGRP(0) 1: Neighbor 192.168.12.1  

(FastEthernet0/1) is resync: peer graceful-restart 

 

Verification: – 

 

R1#show ip route eigrp  

     172.16.0.0/16 is variably subnetted, 3 subnets, 2 masks 

D 172.16.0.0/23 is a summary, 00:00:57, Null0 

 

R2#show ip route eigrp  

     172.16.0.0/23 is subnetted, 1 subnets 

D 172.16.0.0 [90/409600] via 192.168.12.1, 00:00:15, FastEthernet0/1 

 

R2#ping 172.16.0.1 

 

Type escape sequence to abort. 

Sending 5, 100-byte ICMP Echos to 172.16.0.1, timeout is 2 seconds: 

!!!!! 

Success rate is 100 percent (5/5), round-trip min/avg/max = 8/10/12 ms 

 

After summarization also we can ping 172.16.0.1 hence this network is reachable.

HSRP Configuration: Explained

by
hsrp configuration
hsrp configuration

HSRP is a protocol that helps to achieve the failover. With the help of HSRP, we can configure active and standby routers and that goal is achieved with the help of a virtual IP. When active goes down, the standby router comes to the rescue. Let us understand the Cisco HSRP Configuration.

Given below is the topology that will help us understand the HSRP configuration.

hsrp configuration cisco

R1 is configured with 192.168.1.1 and R2 is configured with 192.168.1.2.  

192.168.1.254 is the virtual IP. 

  

R1(config)#interface GigabitEthernet0/0/0 

R1(config-if)#ip address 192.168.1.1 255.255.255.0 

R1(config-if)#no shutdown  

R1(config-if)#standby 1 ip 192.168.1.254 

R1(config-if)#exit 

 

%HSRP-6-STATECHANGE: GigabitEthernet0/0/0 Grp 1 state Standby -> Standby 

This message will pop up. 
R1 is now a standby router. 
Why so? 

Since we have not configured any priority, and the default priority is 100. So the router with a lesser IP Address becomes the standby while the router with a Higher IP address becomes an Active router. 

Let's configure R2.

R2(config)#interface GigabitEthernet0/0/1 

R2(config-if)#ip address 192.168.1.2 255.255.255.0 

R2(config-if)#no shutdown 

R2(config-if)#standby 1 ip 192.168.1.254 

R2(config-if)#exit 

 

 

%HSRP-6-STATECHANGE: GigabitEthernet0/0/1 Grp 1 state Standby -> Active 

R2 becomes an active router since priority is 100 which is default but it has a Higher IP Address. 

Verification

R1#show standby 

 

GigabitEthernet0/0/0 – Group 1 

State is Standby 

8 state changes, last state change 00:18:38 

Virtual IP address is 192.168.1.254 

Active virtual MAC address is 0000.0C07.AC01 

Local virtual MAC address is 0000.0C07.AC01 (v1 default) 

Hello time 3 sec, hold time 10 sec 

Next hello sent in 1.285 secs 

Preemption disabled 

Active router is 192.168.1.2 

Standby router is local 

Priority 100 (default 100) 

Group name is hsrp-Gig0/0/0-1 (default) 

R2#show standby  

 

GigabitEthernet0/0/1 – Group 1 

State is Active 

5 state changes, last state change 00:05:14 

Virtual IP address is 192.168.1.254 

Active virtual MAC address is 0000.0C07.AC01 

Local virtual MAC address is 0000.0C07.AC01 (v1 default) 

Hello time 3 sec, hold time 10 sec 

Next hello sent in 0 secs 

Preemption disabled 

Active router is local 

Standby router is 192.168.1.1 

Priority 100 (default 100) 

Group name is hsrp-Gig0/0/1-1 (default) 

Let us configure the priority value and make R1 an Active Router. 

R1(config)#interface GigabitEthernet0/0/0 

R1(config-if)#ip address 192.168.1.1 255.255.255.0 

R1(config-if)#no shutdown  

R1(config-if)# standby 1 ip 192.168.1.254 

R1(config-if)# standby 1 priority 110 

R1(config-if)# standby 1 preempt 

%HSRP-6-STATECHANGE: GigabitEthernet0/0/0 Grp 1 state Speak -> Standby 

 

%HSRP-6-STATECHANGE: GigabitEthernet0/0/0 Grp 1 state Standby -> Active 

R1 goes from standby to Active since priority is set to 110 which is higher than default priority configured on R2 i.e. 100 

R2(config)#interface GigabitEthernet0/0/1 

R2(config-if)#ip address 192.168.1.2 255.255.255.0 

R2(config-if)#no shutdown 

R2(config-if)#standby 1 ip 192.168.1.254 

R2(config-if)# standby 1 priority 100 

%HSRP-6-STATECHANGE: GigabitEthernet0/0/1 Grp 1 state Speak -> Standby 

The “preempt” here in HSRP is used to specify that a router with a higher priority should automatically take back the role of the active (primary) router when it becomes available again after a failure. 

Verification

R1#show standby  

GigabitEthernet0/0/0 – Group 1 

State is Active 

5 state changes, last state change 00:02:11 

Virtual IP address is 192.168.1.254 

Active virtual MAC address is 0000.0C07.AC01 

Local virtual MAC address is 0000.0C07.AC01 (v1 default) 

Hello time 3 sec, hold time 10 sec 

Next hello sent in 1.966 secs 

Preemption enabled 

Active router is local 

Standby router is 192.168.1.2 

Priority 110 (configured 110) 

Group name is hsrp-Gig0/0/0-1 (default)

R2#show standby  

GigabitEthernet0/0/1 – Group 1 

State is Standby 

3 state changes, last state change 00:02:29 

Virtual IP address is 192.168.1.254 

Active virtual MAC address is 0000.0C07.AC01 

Local virtual MAC address is 0000.0C07.AC01 (v1 default) 

Hello time 3 sec, hold time 10 sec 

Next hello sent in 0.992 secs 

Preemption disabled 

Active router is 192.168.1.1 

Standby router is localbl 

Priority 100 (default 100) 

Group name is hsrp-Gig0/0/1-1 (default)