How to advertise networks in BGP (2024)

Hi,

We r using BGP on our MPLS rtr..

now we have added new network on the existing BGP setup.....but unable to show the same under BGP table.

router bgp xxxxx

bgp log-neighbor-changes

neighbor 10.X.X.185 remote-as XX55

!

address-family ipv4

neighbor 10.X.X.185 activate

no auto-summary

no synchronization

network 10.X.62.0 mask 255.255.255.0 -----> This network we have added

exit-address-family

But not able to get the same using the command sh ip route | i 10.X.62 but we are able to get the entry for 10.X.51 which has been already added.

sh ip route | i 10.X.51

B 10.X.51.0/24 [20/0] via 10.X.X.185, 1w6d

I am working with BGP for the first time......could you people help on the same ?

Regards,

TB

• Labels:
• Network Management

0Helpful

TB

BGP uses the network statement in the configuration to identify what networks you wish to advertise from your local networks. BGP then looks in the local routing table and if it finds a network in the routing table that matches the network statement (and matches the mask also) then BGP will advertise it.

From what you have posted it appears that network 10.x.62.0 is not in the local routing table. If it is not in the local routing table then BGP can not advertise it. So where is 10.x.62.0 coming from and what should be generating that entry for the local routing table. I believe that your issue is that whatever should be putting that route into the routing table is not doing that.

HTH

Rick

0Helpful

In response to Richard Burts

Hi Rick,

Thanks for your response.

You are right that 10.x.62.0 segment is not local. We need to reach that segment from our rtr. Basically, we have added this network on our MPLS rtr which is in one country and the next hop is in another country MPLS rtr (BGP is also running on the same), bwyond this 10.X.62.0 segment is lying.

Also, mentioning you that I have already given the route on the same as well.

So, what should i do ?

Regards,

TB

0Helpful

In response to tuhinbhowmick

Tuhin

as Rick has pointed out, you need to already have a route to that network (component route) whether it is learned via IGP (OSPF etc), connected, static etc. See the below document which should help you.

http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a00800945ff.shtml

You can try put in a static route to null for the network.

0Helpful

In response to velo84

Hi Mark,

As per the doc you have provided where it is saying that, by default auto summary is enabled on BGP and we need to have it enabled to advertise the network. Just fine below the configuration which I have shared earlier .....where no Auto-Summary command is there. So, whether we need to enable the same.

router bgp xxxxx

bgp log-neighbor-changes

neighbor 10.X.X.185 remote-as XX55

!

address-family ipv4

neighbor 10.X.X.185 activate

no auto-summary

no synchronization

network 10.X.62.0 mask 255.255.255.0 -----> This network we have added

exit-address-family

Please check the same and suggest.

Regards,

TB

0Helpful

In response to tuhinbhowmick

TB

If the IP routing table has an entry in it for 10.x.62.0 255.255.255.0 then your existing configuration with no auto-summary should work just fine. If you enable auto summary then your router will advertise 10.0.0.0 /8 as long as there is any network in the routing table within the 10.0.0.0 address space.

Someone disabled auto summary in your configuration. And we do not know enough about your situation to know why they did this or to advise you of the possible impact of enabling auto summary.

My suggestion is to make provision so that the network 10.x.62.0 /24 is present in your IP routing table.

HTH

Rick

0Helpful