BGP configuration issue

Dhiraj Jagdale · ‎05-11-2016

Hi,

We have two ISP links connected at branch end router and BGP is running between branch end and Provider end router. If we done below configuration on branch end router then router is advertise subnet 10.32.34.128/26 to neighbour 10.75.110.177 and subnet 10.32.34.192/26 to neighbour 192.168.183.189 respectively.

But our requirement is to advertise both the subnets 10.32.34.128/25, 10.32.34.128/26 to neighbour 10.75.110.177 and subnets 10.32.34.128/25, 10.32.34.192/26 to neighbour 192.168.183.189 . Require configuration for the same. Thanks in advance.

router bgp 65008
bgp log-neighbor-changes
neighbor 10.75.110.177 remote-as 4755
neighbor 192.168.183.189 remote-as 9583
address-family ipv4
neighbor 10.75.110.177 activate
neighbor 10.75.110.177 prefix-list to-TCL out
neighbor 192.168.183.189 activate
neighbor 192.168.183.189 prefix-list to-Sify out
no auto-summary
no synchronization
network 10.32.34.128 mask 255.255.255.128
network 10.32.34.128 mask 255.255.255.192
network 10.32.34.192 mask 255.255.255.192

ip prefix-list to-TCL description Branch-LAN-Segment
ip prefix-list to-TCL seq 5 permit 10.32.34.128/25
ip prefix-list to-TCL seq 10 permit 10.32.34.128/26

ip prefix-list to-Sify description Branch-LAN-Segment
ip prefix-list to-Sify seq 5 permit 10.32.34.128/25
ip prefix-list to-Sify seq 10 permit 10.32.34.192/26

Borgenstrand · ‎05-12-2016

Hi,

I have a question regarding your subnets, why advertise those subnets? 10.32.34.128/25, 10.32.34.128/26 the second lies within the first one. Same with 10.32.34.128/25, 10.32.34.192/26.
It should be enough just to advertise 10.32.34.128/25 if you have that route in your routing table, BGP should advertise it. If the route is not in the routing table, BGP cannot advertise it.