Understanding show ip bgp x.x.x.x output

Networking CCNP Enterprise
1

Hi @Network_Eric
Hi

R1#show ip bgp 2.2.2.2
BGP routing table entry for 2.2.2.2/32, version 4
Paths: (2 available, best #2, table default)
Advertised to update-groups:
1
Refresh Epoch 1
2, (received & used)
10.1.21.2 from 10.1.21.2 (2.2.2.2)
Origin IGP, metric 0, localpref 100, valid, external
Refresh Epoch 1
2, (received & used)
10.1.12.2 from 10.1.12.2 (2.2.2.2)
Origin IGP, metric 0, localpref 100, valid, external, best

in this output

Q-1 what is the meaning of table default

Q-2 10.1.21.2 from 10.1.21.2 (2.2.2.2)
what is the first 10.1.21.2 referring to ? what problems does it solves?
and what is the secoond 10.1.21.2 referring to ?what problems does it solves?
and what is (2.2.2.2) reffering to ?what problems does it solves?

Q-3
Refresh Epoch 1
2, (received & used)
what is the meaning of "Refresh Epoch 1 " ? what problems does it solves?
and what is the meanig of (received & used) ? what problems does it solves?

Q-4
Advertised to update-groups:
1
what is this referring to ? and what problems does it solves ?

2

Hey Major,

  • Q1: Honestly, not sure. Might be related to which routing table it is working on if you have VRFs? I’ve never looked in to it before.
  • Q2: Those three values in order stand for next hop IP, source router IP, and source router ID. So that tells me that the route to 2.2.2.2/32 is being advertised to you by the BGP neighbor 10.1.21.2, and the route is being advertised in to BGP by that same neighbor, so it is locally connected to that router. The router ID happens to match the route, but BGP does not require that the router ID be routable.
  • Q3: I answered this in another post.
  • Q4: When BGP advertises routes out to neighbors, it has to generate a different update per neighbor. Update groups allow you to group neighbors that are similar together so BGP only needs to generate a single update and send it to all devices in the update group.
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