BGP peer relationships

[Charlotte098]

Hi I'm configuring BGP over a GRE tunnel? Do I have to have BGP across all routers say if the neighbour is a few hops away? I have configured multihop. I have static routes set up so I can ping to and from each router. It's a IBGP and EBGP peer set up. At the moment BGP isn't learning anything. It is in an active state.

[ameya_oke]

Dear Charlotte,

Active state indicates there is a configuration issues.

1)Either next hop is not pingable

2)remote-as misconfiguration

3)update source is not configured in case of peering over loopback configuration

4)neighbor ip is not correctly configured..etc.

IBGP: In case of IBGP config, only connectivity is important, number of hops do not matter.    

EBGP:In this case also, number of hops do not matter unless you have peering over loopback and TTL is kept at 1.

Please check below points fo troubleshooting.

1) In  your EBGP config whether neighbor ip is pingable(using extended ping)

2) remote as is properly configured

3) If loopback is used for bgp peering , check if update source is configured properly and whether thoseloopbacks are pingable from respective routers.

Please rate if helpful.

Ameya

[ameya_oke]

Dear Charlotte,

Also if you have configured peering over loopback, please check below point too.

Assuming an ACL is applied for this tunnel, check if the communication between these loopbacks is allowed.

Ameya

[Marwan ALshawi]

If you use the other end tunnel ip you don't need the multihop ( you can try it ) but make sure the tunnel is up and even after bgp session get establish tunnel destination has to be reachable vis igp or static route to avoid recursive lookup

Also make sure in the bgp table the next hop of the routes showing as the tunnel interface

You might try this command on both ends

neighbor update-source tunnelx.   Where x is the used gre tunnel interface number for this bgp peering

Hope this helps

[Charlotte098]

Hi as far as I can remember I can ping from end to end. I've configured keepalives on the gre tunnel and it is in an up and up state. There is no ACL applied to tunnel and the tunnel source is the loopback interfaces on the routers. I'm using another loopback just for bgp on both routers. I will check to see in the bgp table if the next hop is showing as the tunnel interface. Thanks for the push in the right direction. I will try all those troubleshooting steps.

[ameya_oke]

Dear Charlotte,

From each end just check if the loopbacks uses for neighborship configuration are pingable.

If not you will have to configure static routes for respective loopbacks at both ends.

Also below commands shoud be present.

Config R1:

int loop 0

ip - 2.2.2.2/32

router bgp 100

neighbor 1.1.1.1 remote-as 200

neighbor 1.1.1.1  update-source loopback 0

neighbor 1.1.1.1 ebgp-mul 3 (safer side)

ip route 2.2.2.2 255.255.255.255 tunX

Config R2:

loop 0

ip - 1.1.1.1

/32

router bgp 100

neighbor 2.2.2.2 remote-as 200

neighbor 2.2.2.2  update-source loopback 0

neighbor 2.2.2.2 ebgp-mul 3 (safer side)

ip route 1.1.1.1 255.255.255.255 tunX

Ameya

[Marwan ALshawi]

If you have multiple links/pathes to reach he other end loopback I do recommend you to use the tunnel source and distention as the loopbacks and use igp like eigrp to advertise those loopbacks to be redundant over all pathes

And for bgp peering session use the tunnel ip as the neighbor and source the session from the tunnel interface

This way the tunnel will remain up even if one link or or path is down as the loopbacks wil be reachable via the underlaying  igp

HTH

[ameya_oke]

Dear Charlotte,

I aggree with marwanshawi.

This would reduce your troubleshooting efforts in future.

Cheers!!

Ameya