Hi all. I'm learning BGP for my CCNP BSCI exam, and have been trying to setup a test lab with 3 routers in a full mesh. I've got each router speaking BGP to each other and advertising a local subnet to each other (the subnet is setup on a loopback interface instead of a physical interface). If I do a "show ip bgp", I can see two paths to each subnet, and a "show ip route" tells me the same thing. The problem is when I take down the link from router A to C, the traffic from router A cannot pass through router B to the loopback interface on router C. I've looked and looked, and it's probably simple, but I don't understand what's preventing ping traffic from passing through the alternate routes. If you help out and possibly give a few suggestions, I'd really appreciate it! Thanks.
BGP link reroute problem
Aug 24, 2006
5 Replies
Can you post your configurations and "show ip route" of each router?
Doan
The questions that need to be answered are:
- did you configure iBGP or eBGP or a combination?
- did you configure an IGP (OSPF, ISIS, etc)?
- did you use loopbacks as neighbor addresses?
FW
Here's the configs. Thanks all.
############################
R1 lo0: 192.168.1.1 s0: 10.1.1.1 fa0: 10.3.3.1
Router bgp 1 Network 192.168.1.0 mask 255.255.255.0 Neighbor 10.3.3.2 remote-as 3 Neighbor 10.1.1.2 remote-as 2
------------------------------------
R2 lo0: 192.168.2.1 s0: 10.1.1.2 fa0: 10.2.2.1
Router bgp 2 Network 192.168.2.0 mask 255.255.255.0 Neighbor 10.3.3.2 remote-as 3 Neighbor 10.1.1.1 remote-as 1
-------------------------------------
R3 gi0/0: 10.3.3.2 gi0/1: 10.2.2.2 lo0: 192.168.3.1
Router bgp 3 Network 192.168.3.0 mask 255.255.255.0 Neighbor 10.3.3.1 remote-as 1 Neighbor 10.1.1.2 remote-as 2
###################
Hope this helps. Thanks again.
-Brian
Try, to disable synchronization on all three routers:
router bgp n no synch
FW
Turn on the "debug bgp all" before you disconnect the link between A & C, if possible please post the debug output, then we will be clear what is going on.
Also you may try to relaod the Routing Table by "clear ip route * ". Hope that can help.
Join the Discussion
Have something to add? Share your thoughts — no account required.
Didn't find your answer?
Ask the community — no account required