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
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