BGP with nexus not choosing the right route

[Lim Victor]

Hi all,

I am a problem whereby one of the the routers is not forming bgp peering with one of my nexus.

Please refer to attached diagram.

The reason why it does not form the bgp peering was because it had chosen the wrong bgp route as the best route due to the as-path.

router-5#show ip bgp

BGP table version is 46, local router ID is 192.168.1.1

Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,

              r RIB-failure, S Stale, m multipath, b backup-path, x best-external, f RT-Filter

Origin codes: i - IGP, e - EGP, ? - incomplete

   Network          Next Hop            Metric LocPrf Weight Path

*> 192.168.1.0/24    192.168.1.2               0             0 64982 ?

*                   10.0.0.14             0             0 64982 64982 ?

*> 10.0.0.8/29  0.0.0.0                  0         32768 ?

router-5#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

       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, H - NHRP, l - LISP

       + - replicated route, % - next hop override

Gateway of last resort is not set

      10.0.0.0/8 is variably subnetted, 3 subnets, 3 masks

B        192.168.1.0/24 [20/0] via 192.168.1.2, 00:02:55

C        10.0.0.8/29 is directly connected, GigabitEthernet0/0.901

L        10.0.0.19/32 is directly connected, GigabitEthernet0/0.901

This cause router 2 to not be able to peer with nexus 1 as it does not know how to get to 192.168.1.2. Pinging to Nexus 1(192.168.1.2) from router 2(10.0.0.9) will fail.

How should i influence the route such router 2 will choose 10.0.0.14 as the next hop for 192.168.1.0/24 such that peering can between router 2(10.0.0.9) and Nexus 1(192.168.1.2) can be successful

Thanks.

[Lim Victor]

Hi all,

I am thinking that I should do as-path pretend to influence the routing, right?

Any idea why 192.169.1.2 only has 1 as-path(64982) while 10.0.0.14 has 2 as-path pretended even though it 10.0.0.14 is 1 h away while 192.168.1.2 is 2 hops away.

Thanks.

[e.nieuwstad · Accepted solution]

you are trying to setup a full iBGP mesh i suppose?

Normally you would run a IGP like OSPF or EIGRP to get all the internal routes propagated and then you should be able to create the iBGP neighbours.