BGP Routing Table Entry without Exit Interface

BGP routes that appear in the routing table of a Cisco IOS Layer 3 device will never have an exit interface as part of their entry. They will always have a next hop IP address.

To determine the exit interface, recursive routing is always employed. This is why a BGP route will only appear in the routing table if there is a valid route to the next hop IP.

Here is an example of the BGP table:

R1#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, m - OMP
       n - NAT, Ni - NAT inside, No - NAT outside, Nd - NAT DIA
       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
       H - NHRP, G - NHRP registered, g - NHRP registration summary
       o - ODR, P - periodic downloaded static route, l - LISP
       a - application route
       + - replicated route, % - next hop override, p - overrides from PfR
       & - replicated local route overrides by connected

Gateway of last resort is not set

      2.0.0.0/32 is subnetted, 1 subnets
B        2.2.2.2 [20/0] via 192.168.12.2, 00:00:42

You can see a detailed output here:

R1#show ip route 2.2.2.2
Routing entry for 2.2.2.2/32
  Known via "bgp 1", distance 20, metric 0
  Tag 2, type external
  Last update from 192.168.12.2 00:01:26 ago
  Routing Descriptor Blocks:
  * 192.168.12.2, from 192.168.12.2, 00:01:26 ago
      opaque_ptr 0x7C91AFB92E38
      Route metric is 0, traffic share count is 1
      AS Hops 1
      Route tag 2
      MPLS label: none

If you want to see the recursive lookup for a route, you can check the CEF table:

R1#show ip cef 2.2.2.2
2.2.2.2/32
  nexthop 192.168.12.2 Ethernet0/1