Implementing Basic Route Redistribution

redistribution example

Redistribution is a great way to work with a lot of routing protocols. Now it is time to configure “route redistribution” with an example ! And surely step by step. Please check the figure below :

basic redistribution example

1) Configure EIGRP and OSPF with no summarization. Loopbacks of the router 3 must be configured point-to-point.
Activate full redistribution between OSPF and EIGRP networks. All routers must see all routes on the routing tables. Implement all metrics, pay attention that OSPF external routes shouldn’t increase their metrics.
 Implement distribute-list filter on OSPF network so that just the “odd” loopbacks of the Router 1 is seen. All “even” subnets (including physical networks) shouldn’t be seen from OSPF domain side.
Implement route-map filter so that just /24 routes are seen at EIGRP domain.



R1(config)#router eigrp 100
R1(config-router)#no auto

R2(config)#router eigrp 100
R2(config-router)#no auto



We can’t use because OSPF network is 10.x.x.x.x too !

R2(config)#router ospf 1
R2(config-router)#network area 0

R3(config)#router ospf 1
R3(config-router)#network area 0
R3(config)#interface range loopback0 - 6
R3(conf-if)#ip ospf network point to point     // Point-to-point configuration on router 3 loopbacks//


EIGRP default metric = infinite
OSPF default metric = 20     // Metric of EIGRP is infinite while metric of OSPF is 20 while passing over a network which uses another protocol via redistribution //

R2(config)#router ospf 1
R2(config-router)#redistribute eigrp 100 subnets     // Redistribution from EIGRP to OSPF network //
R3# sh ip route
... [110/20] via

Route in EIGRP domain appears as an O(OSPF) route, not a D(EIGRP) metric=20 , E2 defaultly

R2(config)#router eigrp 100
R2(config-router)#redistribute ospf 1

If you run the “show ip route” after these commands ,you can’t see any entries in the routing table because of the infinite metric. So that we will use the commands below to resolve this issue

redistribute ospf metric 100 100 100 100 100     //  First 100 belongs to EIGRP BW, second DELAY , third RELIABILITY //

R3# sh ip route
D EX [170/2613020] via

R2 (config)# access-list 1 permit
R2 (config)# access-list 1 permit
R2 (config)# access-list 1 permit

R2(config)#router ospf 1
R2(config-router)#distribute-list 1 out     //  OUT = While going to Router 3 from Router 2 //
R3# sh ip route 

R2(config)# ip prefix-list APPLE permit le 24

You can permit a spesific subnet via prefix-list. In this command we are permitting and less than or equal to. (le) For instance / 16 will be permitted

R2(config)#route-map FILTER_OSPF_TO_EIGRP
R2(config-route-map)#match ip aress prefix-list APPLE
R2(config-route-map)#router eigrp 100
R2(config-route-map)#redistribute ospf 1 metric 100 100 100 100 100 route-map FILTER_OSPF_TO_EIGRP

*** We could do this last step via distribute-list too

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