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New Member

BGP between PE-CE

Dear all,

In my lab, I have 2P, 2 PE and 2 CE and try to build mpls vpn cloud.

I want to use BGP as a routing between PE-CE.

CE-A ------- PE-A ------ P ---- P ------ PE-B ----CE-B

Sample config:



router bgp 65000


address-family ipv4 vrf V79:vpntest

redistribute connected

redistribute static

neighbor remote-as 65499

neighbor update-source Serial3/0

neighbor activate

no auto-summary

no synchronization



in CE


router bgp 65499

no synchronization

bgp log-neighbor-changes

network mask

neighbor remote-as 65000

neighbor update-source Serial2/0

no auto-summary


The issue is :

1) In CE-B when I show ip route, it doesn't display route that coming from CE-A ie loopback IP, FE IP etc although PE-B have the route. What do i need to configure if I want CE-B receive the route. The reason why I need to have the routes is for ISDN back-up between CE to CE

any advice,



New Member

Re: BGP between PE-CE

You have not advertised your loopback ip into BGP in CE

Run eigrp over your ISDN and use dialer watch list

Use a prefix list via a route-map to block the advertisement of the loopback at the called end.

This way you can have a watchlist on the loopback to bring up your ISDN.

Note: For this method both routers need to learn the loopback routes dynamically and on the bbackup link the caller doesn't need to know the loopback

Router A

dialer watch-list

Router B

router BGP as<>

neighbour< on Dialer> route-map backup out


route-map backup deny 5

match ip address prefix-list Lo0


ip prefix-list Lo0 seq 5 permit < [Lo0 IP] [mask}>

New Member

Re: BGP between PE-CE

If he is not injecting the CE loopback into BGP, how could the PE-B have the route? Perhaps there is another issue here?

Why are you blocking the advertisement of Router B's loopback into BGP. Won't this cause Router A to constantly dial the ISDN, since the watched route is not present?



New Member

Re: BGP between PE-CE

Hi there,

I only want CE-B to see the loopback IP or CE-A. The reason is CE-B will make a connection and CE-B seems to be at HQ.

CE-A will only received default router from BGP peer, PE-A and have static route

ip route 240 <--next hop ISDN. If LL between PE-A and CE-A down, then ISDN will kick-off.

In CE-B, there will be static route to loopback IP of CE-A

ie ip route 240.

If CE-B did not received this route from PE-B, it will always make an ISDN call if any traffic that want to reach loopback ip CE-A although LL PE-A and CE-A is up.

I found one solution and somehow it's work.

Let say main IBGP is AS1111. Before this, PE-A TO CE-A and PE-B to CE-B using same AS no ie 65499. If I change PE-A to CE-A using different AS ie 65498, everyone can each others.

Conclusion, all branches will use same AS and HQ another AS.

It's work but not a good design. Maybe someone can assist me on this.

It's quite tricky for me (my BGP not that good) where i need to apply route-map in and out and have different weight and prepend in CE-B in order to make everything work.


Re: BGP between PE-CE


Your problem is that your routes comming from AS 65499 going through

AS 1111 and coming again to AS 65499. PE-B will not propagate it because

its again the same AS......loop prevention of BGP.

So you could implement the as override to overgo this situation so you can

use the same AS on both side

neighbor as-override

If you have single access for a subnet thats no problem to override the as number. As soon as you have redundant connection into your MPLS/VPN you

should use some mechanisme to prevent loops. In this case you could use

the site of origin extended community.

So hope it helps


New Member

Re: BGP between PE-CE

Hi Roger,

It works. I need to improve my bgp knowledge from now on :)

Now I have complete solutions for my network.

For fine-tuning, when primary LL down, there were 23 packets loss before ISDN start to kick-off and routing fully converges and took only 3 packets loss from ISDN to primary after LL is up. I'try not to change any default value on BGP, but the if anyone have a suggestion, you are most welcome to share with me and us as well.

once again, thanks for everyone.



Re: BGP between PE-CE

Hi mdshah

I am happy that it works now for you. I just like to give

you a good tip for a book about BGP.

It's from Bassam Halabi and the book is called

"Internet Routing Architectures" (ISBN 1-56205-652-2)

For me it's the book when there is something about BGP.



New Member

Re: BGP between PE-CE

Hi again,

Yes, I have the book . And I am study very hard now to master the bgp :)

many things that I learn from this including output from sh ip bgp etc ..and the BGP criterias on how to choose the route.

I saw about as-overide part and maybe before this not know when to use it.

Thanks buddy.