Cisco Support Community
cancel
Showing results for 
Search instead for 
Did you mean: 
Announcements

Welcome to Cisco Support Community. We would love to have your feedback.

For an introduction to the new site, click here. And see here for current known issues.

New Member

BGP help

I have a lab setup for learning BGP. I'm trying to understand why I cannot ping the loopback interface of router c from router b.

Three routers.

Router A -

Lo0:10.252.1.1/32

S0:192.168.27.1/30

S1:192.168.27.5/30

S2:192.168.27.9/30

router bgp 65000

no synchronization

bgp log-neighbor-changes

network 10.252.1.1 mask 255.255.255.255

neighbor 192.168.27.2 remote-as 65001

neighbor 192.168.27.6 remote-as 65003

neighbor 192.168.27.10 remote-as 65002

Router B:

Lo0:10.252.1.5

S0:192.168.27.2

router bgp 65001

no synchronization

bgp log-neighbor-changes

network 10.252.1.5 mask 255.255.255.255

neighbor 192.168.27.1 remote-as 65000

Router C

Lo0:10.252.1.9

S0:192.168.27.10

router bgp 65002

no synchronization

bgp log-neighbor-changes

network 10.252.1.9 mask 255.255.255.255

neighbor 192.168.27.9 remote-as 65000

8 REPLIES
Hall of Fame Super Blue

Re: BGP help

What do the routing tables on B & C show ?

Have you tried doing an extended ping with the source of the ping as the loopback address of router B. You are not advertising the p2p 192.168.27.x networks - is there a route on C for B's 192.168.27.0/30 network ? If not and the ping goes out with a source of 192.168.27.2 then C does not how to get back.

HTH

New Member

Re: BGP help

Thanks for the help. I tried doing an extended ping with src as the loopback and that didn't work. Unless I was doing it wrong. I did however advertise the wan networks and that worked. Thanks for the help.

New Member

Re: BGP help

Hello,

If you send an ping from router C it will have as source address 192.168.27.9. This address is unknown for router B. Try an extended ping to router B with source address loopback0 on router C. This should get an reply.

regards

Rogier

New Member

Re: BGP help

Thanks for the help. I tried that and it didn't work. Not sure why.

New Member

Re: BGP help

My bad. Using extended ping with the source as the Loopback ip address does work. Thanks

New Member

Re: BGP help

Hi,

Just give no auto-summary on all 3 routers and see.

rgrds,

hardik

New Member

Re: BGP help

I think since the routers are advertising only their loopback addresses, RouterB doesn't know hot to get to RouterC's Serial interface therefore the next hope is unreachable (it has to use Router C's serial address to get to the loopback interface. on RouterA you should add next-hop self command for the neigbors. if you use that, the router will have valid next hop address

on router A:

neighbor 192.168.27.2 next-hop-self

neighbor 192.168.27.10 next-hop-self

should fix

cheers

Tayfun

New Member

Re: BGP help

Hello,

This is not correct. Using next-hop-self is for use between IBGP peers not EBGP peers as is the case here.

Regards

Rogier

122
Views
0
Helpful
8
Replies
CreatePlease to create content