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Cisco MPLS BGP Routing with backup ISP at another site

Posted on 2011-02-24
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Last Modified: 2012-08-14

We have 4 sites.  All on MPLS with BGP routing.

Site A has the primary Internet connection.  BGP is configured with default-originate to pass the default route to the other MPLS sites.

Site B has a new Cable Internet installed  to another ISP as backup.  We want to re-configure BGP so if the primary location circuit drops or if the Internet at the primary location drops, Site B will become the backup and Internet will continue out the backup path.  Site B's Internet has a ASA in place on the DSL line.

Then once Site A comes back online or the Internet there is restored, Site B's default route reverts back to Site A and the rest of the sites follow suit..

Any configuration examples available?  Your assistance is much appreciated!

   Cisco MPLS BGP Backup ISP
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Question by:tknowsley
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rfc1180 earned 2000 total points
ID: 34974345
Simple config:

On Site B

ip route 0.0.0.0 0.0.0.0 'default-gateway ip of Comcast'

access-list 1 permit 0.0.0.0

route-map default permit 10
match ip address 1
set metric 100

router bgp xxx
neighbor x.x.x.x route-map default out

You might want to setup peer groups for your internal routers and then you will only have to update the peer group rather then adding neighbor statement for all your internal routers with the route-map.

Ensure that you clear ip bgp * soft out



Billy
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by:tknowsley
ID: 34976445
Billy - Thanks for your input.  Your configuration above worked as planned with a little tweaking.  I'm going to run a few more tests, but I think we've got it.  Here's what I changed.

I added a cost of 250 to the default route @ Site B, without it, Site B would automatically use the static route and not get the REAL default route via BGP from Site A.

Using the commands you stated above, the route would get added to the Site C & Site D, but when Site A came back online, Site C&D would revert back but Site B would not revert back for some reason it would stay static.   So playing around I removed the neighbor statement in your config ("neighbor x.x.x.x route-map default out")
and added this line below which seems to solve the issue.

neighbor XX.XX.XX.XX default-originate route-map default-route

I'm going to run some more tests this weekend.  Thanks for your help!
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by:rfc1180
ID: 34976768
Glad you got it work, yeah the config as stated was just a simple config and expected some tweaking based on your environment. That was just off the top of my head and should have mentioned that. All in all, glad you got it working.

Billy
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