BGP alternate path missing

chapapa

Hi guys I have these topology just like on the cbt nuggets. I configured all routers with bgp and all are neighbors. My problem is, I will use this topology for manipulating the path attributes but my alternate paths are missing from R1, R2, ad R3 for the loopbacks 150.1.50.0, 150.2.50.0, 200.50.1.0 and 200.50.2.0.

I've once used this topology and able to see the alternate routes and able to manipulate the attributes. I just did the same configurations just like before but now the alternate routes are not appearing. help!

R1:
router bgp 5500
no synchronization
bgp log-neighbor-changes
neighbor 2.2.2.2 remote-as 5500
neighbor 2.2.2.2 update-source Loopback0
neighbor 2.2.2.2 next-hop-self
neighbor 3.3.3.3 remote-as 5500
neighbor 3.3.3.3 update-source Loopback0
neighbor 3.3.3.3 next-hop-self
no auto-summary

R2:
router bgp 5500
no synchronization
bgp log-neighbor-changes
neighbor 1.1.1.1 remote-as 5500
neighbor 1.1.1.1 update-source Loopback0
neighbor 1.1.1.1 next-hop-self
neighbor 3.3.3.3 remote-as 5500
neighbor 3.3.3.3 update-source Loopback0
neighbor 3.3.3.3 next-hop-self
neighbor 4.4.4.4 remote-as 777
neighbor 4.4.4.4 ebgp-multihop 2
neighbor 4.4.4.4 update-source Loopback0
no auto-summary
!
ip route 4.4.4.0 255.255.255.0 30.1.24.2

R3:
router bgp 5500
no synchronization
bgp log-neighbor-changes
neighbor 1.1.1.1 remote-as 5500
neighbor 1.1.1.1 update-source Loopback0
neighbor 1.1.1.1 next-hop-self
neighbor 2.2.2.2 remote-as 5500
neighbor 2.2.2.2 update-source Loopback0
neighbor 2.2.2.2 next-hop-self
neighbor 6.6.6.6 remote-as 777
neighbor 6.6.6.6 ebgp-multihop 2
neighbor 6.6.6.6 update-source Loopback0
no auto-summary
!
ip route 6.6.6.0 255.255.255.0 30.1.36.2

R5:
router bgp 911
no synchronization
bgp log-neighbor-changes
neighbor 4.4.4.4 remote-as 777
neighbor 4.4.4.4 ebgp-multihop 2
neighbor 4.4.4.4 update-source Loopback2
neighbor 7.7.7.7 remote-as 711
neighbor 7.7.7.7 ebgp-multihop 2
neighbor 7.7.7.7 update-source Loopback2
no auto-summary
!
ip route 4.4.4.0 255.255.255.0 30.1.10.1
ip route 7.7.7.0 255.255.255.0 30.1.14.2

R7:
router bgp 711
no synchronization
bgp log-neighbor-changes
neighbor 5.5.5.5 remote-as 911
neighbor 5.5.5.5 ebgp-multihop 2
neighbor 5.5.5.5 update-source Loopback2
neighbor 6.6.6.6 remote-as 777
neighbor 6.6.6.6 ebgp-multihop 2
neighbor 6.6.6.6 update-source Loopback2
no auto-summary
!
ip route 5.5.5.0 255.255.255.0 30.1.14.1
ip route 6.6.6.0 255.255.255.0 30.1.11.1

tell me if you need more information about my configs. thanks!

powmia

You need to enable bgp multihop (ibgp or ebgp, depending on the topology). BGP has distance vector traits, meaning it only selects a single best path and discards the rest. The multihop feature allows BGP to install multiple paths prior to moving onto the tie-breakers at the bottom of the desicion process.

chapapa

powmia wrote: »

You need to enable bgp multihop (ibgp or ebgp, depending on the topology). BGP has distance vector traits, meaning it only selects a single best path and discards the rest. The multihop feature allows BGP to install multiple paths prior to moving onto the tie-breakers at the bottom of the desicion process.

from a multihop of 2 which I had configured, I will change it to a higher hop so that It can reach my routers?

xXErebuS

You need to configure multipath not multihop. Multihop is when your BGP peer is more than one hop away (i.e. a router in between); it changes the TTL of the packets.

powmia

lol, that's what i meant, apparently not what i typed. Configured via maximum paths, no options = ebgp, or can specify ibgp.

chapapa

guys let me clarify something, what I meant on my 1st post is that I can't see my alternate paths in the BGP table. sorry for not clarifying that one. After troubleshooting the network. I found out that my neighbor state between R3 and R6 is Active which is caused by the wrong next hop address on the static route of R3 (though the CLI accept that syntax since 30.1.36.2 was the local interface of R3). Now I can see my alternate paths and I was able manipulate the attributes. Thank you for the introducing me Multipath I learned about it after asking help from google ^^, thank you guys for your help!

@mods: please closed this thread. Problem Solved!