05-10-2014 02:04 PM - edited 03-04-2019 10:57 PM
Hello
I've been trying to configure a WAN that uses eBGP in order to exchange routing data, but nothing seems to work.
The configuration is very basic and yet I can't receive any BGP packets.
router bgp 6774
no synchronization
bgp router-id 2.2.2.2
bgp log-neighbor-changes
network 2.2.2.2 mask 255.255.255.255
neighbor 1.1.1.1 remote-as 12666
neighbor 1.1.1.1 update-source Loopback0
neighbor 3.3.3.3 remote-as 9031
neighbor 3.3.3.3 ebgp-multihop 255
neighbor 3.3.3.3 update-source Loopback0
no auto-summary
Is there something blatantly wrong with my configuration?
Thank you for your help.
05-10-2014 06:12 PM
Hi,
You need to enable ebgp multihop on other routers which is missing.
On R2, enable ebgp multihop for 1.1.1.1
router bgp 6774 no synchronization bgp router-id 2.2.2.2 bgp log-neighbor-changes network 2.2.2.2 mask 255.255.255.255 neighbor 1.1.1.1 remote-as 12666 neighbor 1.1.1.1 update-source Loopback0 neighbor 3.3.3.3 remote-as 9031 neighbor 3.3.3.3 ebgp-multihop 255 neighbor 3.3.3.3 update-source Loopback0
On R5 and R6 enable ebgp multihop for all neighbors,
router bgp 9031 no synchronization bgp log-neighbor-changes neighbor 1.1.1.1 remote-as 12666 neighbor 1.1.1.1 update-source Loopback0 neighbor 2.2.2.2 remote-as 6774 neighbor 2.2.2.2 update-source Loopback0
router bgp 12666 no synchronization bgp router-id 1.1.1.1 bgp log-neighbor-changes network 1.1.1.1 mask 255.255.255.255 neighbor 2.2.2.2 remote-as 6774 neighbor 2.2.2.2 update-source Loopback0 neighbor 3.3.3.3 remote-as 9031 neighbor 3.3.3.3 update-source Loopback0
By default, eBGP will expect from directly connected address. If it is between loopback, you need to enable multihop to bring the session up.
-Nagendra
05-11-2014 02:23 AM
Hello
Thank you for the fast response!
I've added multihop as you've requested along with some other config and it's working partially: the routers that are directly connected receive packets from each other, but the ones that aren't receive 0 packets (R2 and R6).
Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd
1.1.1.1 4 12666 8 7 15 0 0 00:00:32 4
3.3.3.3 4 9031 0 0 0 0 0 never Active
10.10.10.10 4 12666 8 9 15 0 0 00:01:08 4
11.11.11.10 4 12666 0 0 0 0 0 never Idle
11.11.11.20 4 9031 0 0 0 0 0 never Idle
The configuration:
router bgp 6774
no synchronization
bgp log-neighbor-changes
network 2.2.2.2 mask 255.255.255.255
network 10.10.10.20 mask 255.255.255.255
neighbor 1.1.1.1 remote-as 12666
neighbor 1.1.1.1 ebgp-multihop 255
neighbor 1.1.1.1 update-source Loopback0
neighbor 3.3.3.3 remote-as 9031
neighbor 3.3.3.3 ebgp-multihop 255
neighbor 3.3.3.3 update-source Loopback0
neighbor 10.10.10.10 remote-as 12666
neighbor 11.11.11.10 remote-as 12666
neighbor 11.11.11.20 remote-as 9031
no auto-summary
router bgp 12666
no synchronization
bgp log-neighbor-changes
network 1.1.1.1 mask 255.255.255.255
network 10.10.10.0 mask 255.255.255.0
network 10.10.10.10 mask 255.255.255.255
network 11.11.11.0 mask 255.255.255.0
network 11.11.11.10 mask 255.255.255.255
neighbor 2.2.2.2 remote-as 6774
neighbor 2.2.2.2 ebgp-multihop 255
neighbor 2.2.2.2 update-source Loopback0
neighbor 3.3.3.3 remote-as 9031
neighbor 3.3.3.3 ebgp-multihop 255
neighbor 3.3.3.3 update-source Loopback0
neighbor 10.10.10.20 remote-as 6774
neighbor 11.11.11.20 remote-as 9031
no auto-summary
router bgp 9031
no synchronization
bgp log-neighbor-changes
network 3.3.3.3 mask 255.255.255.255
network 11.11.11.0 mask 255.255.255.0
network 11.11.11.20 mask 255.255.255.255
neighbor 1.1.1.1 remote-as 12666
neighbor 1.1.1.1 ebgp-multihop 255
neighbor 1.1.1.1 update-source Loopback0
neighbor 2.2.2.2 remote-as 6774
neighbor 2.2.2.2 ebgp-multihop 255
neighbor 2.2.2.2 update-source Loopback0
neighbor 10.10.10.10 remote-as 12666
neighbor 10.10.10.20 remote-as 6774
neighbor 11.11.11.10 remote-as 12666
no auto-summary
Could you also help me out with this one?
Thanks again.
05-12-2014 12:12 AM
Hi,
are you able to Ping between the Lopopbacks you are using as BGP source/destinations?
Don't forget TCP connectivity is a prerequisite to establish a BGP session.
As I don't see any static routes in your configs, how do the routers know where to forward the packets with the other router's Loopback destination IP?
Best regards,
Milan
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