L3VPN using BGP protocol

Routing & Switching BGP
1

Hello Team,

One of our customers requested me to provision a L3VPN using BGP. To acheive this, we have 2 segment (A-to-B & C-to-D). A and C as ISP _ B and D as CEs.

When i check routes i am receiving, below is the output:

BGP table version is 2291, local router ID is 1.0.0.5
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal, 
              r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter, 
              x best-external, a additional-path, c RIB-compressed, 
Origin codes: i - IGP, e - EGP, ? - incomplete
RPKI validation codes: V valid, I invalid, N Not found

     Network          Next Hop            Metric LocPrf Weight Path
Route Distinguisher: 22690:8 (default for vrf EQUITY-MPLS)
 **r   172.27.10.0/30   172.27.10.2              0             0 65006 i**

Total number of prefixes 1

why am i getting rib-failure??? how can i fix this? what are the issues caused by rib-failure?

Thank you for your consideration.

JP

2

Hello JP,

You get a RIB failure when BGP can’t install something in the routing table. Usually this happens when you can’t resolve the next hop or when there is another route with a better (lower) AD already installed in the routing table.

Here’s a quick example:

R3#show ip bgp 
BGP table version is 2, local router ID is 192.168.34.3
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal, 
              r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter, 
              x best-external, a additional-path, c RIB-compressed, 
              t secondary path, 
Origin codes: i - IGP, e - EGP, ? - incomplete
RPKI validation codes: V valid, I invalid, N Not found

     Network          Next Hop            Metric LocPrf Weight Path
 *    4.4.4.4/32       192.168.13.1                           0 1 2 4 i
 *>                    192.168.34.4             0             0 4 i
R3#show ip route bgp        
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
       a - application route
       + - replicated route, % - next hop override, p - overrides from PfR

Gateway of last resort is not set

      4.0.0.0/32 is subnetted, 1 subnets
B        4.4.4.4 [20/0] via 192.168.34.4, 00:01:43

Let’s add a static route for 4.4.4.4/32 so BGP can’t install the route in the routing table anymore:

R3(config)#ip route 4.4.4.4 255.255.255.255 192.168.34.5

You now get an error:

R3#show ip bgp
BGP table version is 3, local router ID is 192.168.34.3
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal, 
              r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter, 
              x best-external, a additional-path, c RIB-compressed, 
              t secondary path, 
Origin codes: i - IGP, e - EGP, ? - incomplete
RPKI validation codes: V valid, I invalid, N Not found

     Network          Next Hop            Metric LocPrf Weight Path
 r    4.4.4.4/32       192.168.13.1                           0 1 2 4 i
 r>                    192.168.34.4             0             0 4 i
R3#show ip bgp rib-failure 
  Network            Next Hop                      RIB-failure   RIB-NH Matches
4.4.4.4/32         192.168.34.4        Higher admin distance              n/a

Rene

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3

Thanks Rene, i managed to resolve the issue with the help of your explanations. thank you

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