Redistribution between OSPF and EIGRP

[Hamed Karimi]

Hello everyone,

In this topology, we want to redistribute from EIGRP to OSPF on both R1 and R2.

67.67.67.67 is already an external route on R4 (AD 170). First, we redistributed on R1 and then on R2.

On R1:

On R2:

As you can see R1 sees the 67.x.x.x.x route as Eigrp but R2 sees it as OSPF. However, OSPF AD 110 is lower than EIGRP external 170 for both of them, so why R1 does not replace the OSPF route. 

R1 has it just in the OSPF database, not the routing table.

Quick Note: The router that I put the redistribute command first will see it as external EIGRP and the other router sees it as external OSPF.

Thanks

[Georg Pauwen]

Hello,

post the full running configs of all three routers, and indicate how 67.67.67.67 gets into R4 as an external route.

[Hamed Karimi]

I just put a static route on R4 and redistributed into EIGRP to simulate an EIGRP external route.

R1:

interface GigabitEthernet0/0
ip address 172.20.20.1 255.255.255.0
!
interface GigabitEthernet1/0
ip address 10.200.200.1 255.255.255.0
negotiation auto

!
router eigrp 100
network 0.0.0.0
!
router ospf 1
redistribute eigrp 100 subnets
network 172.20.20.0 0.0.0.255 area 0
-------------------------------------

R2:

interface GigabitEthernet0/0
ip address 172.20.20.3 255.255.255.0
!
interface GigabitEthernet1/0
ip address 10.40.40.1 255.255.255.0
negotiation auto
!
router eigrp 100
network 0.0.0.0
!
router ospf 1
redistribute eigrp 100 subnets
network 172.20.20.0 0.0.0.255 area 0
!

-----------------

R4:
interface GigabitEthernet1/0
ip address 10.200.200.2 255.255.255.0
negotiation auto
!
interface GigabitEthernet2/0
ip address 10.40.40.2 255.255.255.0
negotiation auto
!
router eigrp 100
network 0.0.0.0
redistribute static
!
ip route 67.67.67.67 255.255.255.255 10.30.30.2
!

[Jon Marshall · Accepted solution]

Before redistribution both R1 and R2 will have an external EIGRP route for 67.67.67.67 in their routing table. 

When you redistribute on R1 it now advertises an OSPF route (AD 110) to R2 and because that is a better AD than the EIGRP route (AD 170) it replaces the EIGRP route in the routing table and because only routes in the routing table can be redistributed the EIGRP route is not redistributed into OSPF.

So R1 only has an EIGRP for that prefix because R2 never redistributes it into OSPF.

Jon

[Hamed Karimi]

Right.

Thank you