iBGP question

[paublo]

Heres how the network is setup.

Router A (customer) which connects to router B (my router) . Router B is connection to router C (my 2nd router) over iBGP.

My BGP customer advertises 5 routes. The router directly connected to my customer’s bgp router (Router A) shows all 5 routes when I do a (sh ip bgp sum).
Router C (my 2nd router iBGP) only shows these 5 router when I type “show ip bgp sum” for about a 1:15 to 1:30 minutes then the routes disappear from State/PfxRcd.

When I do a show ip bgp on router B for one of the received routes from router A (cust router) it’s says:

Paths: (2 available, best #1, table Default-IP-Routing-Table)
Multipath: iBGP
Not advertised to any peer

The second best route being from my customer (router A) and the 1st best route being from Router C (my second iBGP router)


Now on Router C, where I’m confused when I do show ip bgp for the same route I see.

Paths: (2 available, best #1, table Default-IP-Routing-Table)
Advertised to update-groups:
1

Both routes being from my two up streams on that router.

My confusion is when I do a show ip bgp sum <router B’s neighbor address> I see 5 routes under State/PfxRcd then after a minute or two they disappear.

Is this normal ibgp behavior? Are the router listed under State/PfxRcd only routes that are inserted in the routing table?

 

[baddos]

How is router b and c connected?

Are there any route-maps or prefix-lists associated w/ either router b or c?

 

[paublo]

b and c are connected vi ethernet. what ended up happening is router b see's the advertised routes from router A. when router B advertises that to its ibgp neighbor, router C, that router will display the received prefixes for 2 min or so then removing them.

looking more into this i think what is happening is normal bgp behavior. when i looked at router B the best path to the advertised networks from router A, where through another upstream and then through router A.

When looking at router B the best 2 paths where through my customers upstreams. Since the 2 best routes are not through router B, the routes get removed in sh ip bgp sum on router c.

 

[baddos]

Your customer (router a) is connected via eBGP correct?

 

[fabiangp]

try to debug ip bgp keepalives on C. What are your bgp timers? on both routers.

 

[paublo]

baddos, that is correct.

i think what im seeing a normal igp behavior, because router C is not using the routes received from router B when you do a sh ip bgp on router you will not the receives prefixes once router C recalculates the best 2 routes, which in this case do not come from router B.