Originate PE to CE Network only if PE/CE BGP Peer Up

Answered Question
Mar 21st, 2007
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Is there a way to advertise a PE/CE network link into a VPN only if the CE has established a BGP peering relationship with the PE? I would like the PE to handle this rather than rely on the CEs to originate the route.


Here is what I've found so far:

PE with mulitple BGP Peers and vrf interfaces configured for a specific VPN. Interfaces are either Frame-relay or Ethernet so PE interface is always up/up.


If neither the PE or CE routers originate the PE/CE link then the link is not advertised to any other peers = BAD.


If the PE originates with either network statement or redistribute connected then all PE/CE links are advertised even if there is no CE yet configured on some of the interfaces.


My goal is to only originate the PE/CE network from the PE to other VPN routers if the PE/CE peer is established. Otherwise the network should not appear in the BGP/RT.


Hope that makes sense.

Correct Answer by mheusinger about 10 years 1 week ago

Hi,


the simplest approach would be to announce networks through the CE. If this is not feasible (why?), then one other feature could help you: "Configuring Reliable Static Routing Backup Using Object Tracking: Static Routing Examples"

http://www.cisco.com/en/US/products/sw/iosswrel/ps5413/products_feature_guide09186a00801d862d.html#wp1071672


Based upon connectivity (f.e. ping) you can insert or remove a static route from the IP routing table. This combined with a BGP network statement or redistributio might help you. Be aware however, that the PE-CE network is directly connected and a static route with exact the same network would not be inserted into the routing table. Instead you could use host routes.

You further need to check, whether object tracking is supported on your PEs.


Hope this helps! Please use the rating system.


Regards, Martin

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Correct Answer
mheusinger Wed, 03/21/2007 - 06:05
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Hi,


the simplest approach would be to announce networks through the CE. If this is not feasible (why?), then one other feature could help you: "Configuring Reliable Static Routing Backup Using Object Tracking: Static Routing Examples"

http://www.cisco.com/en/US/products/sw/iosswrel/ps5413/products_feature_guide09186a00801d862d.html#wp1071672


Based upon connectivity (f.e. ping) you can insert or remove a static route from the IP routing table. This combined with a BGP network statement or redistributio might help you. Be aware however, that the PE-CE network is directly connected and a static route with exact the same network would not be inserted into the routing table. Instead you could use host routes.

You further need to check, whether object tracking is supported on your PEs.


Hope this helps! Please use the rating system.


Regards, Martin

er-moffat Thu, 03/22/2007 - 11:19
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I agree about announcing through the CE but what I'm trying to do is mock up a network for a customer where the service provider will be automatically originating the PE/CE links once the peer comes up. Not sure how they are accomplishing it but suspect they must be doing some sort of check on the peering relationship before injecting the routes. Not sure what sort of tools they would use for that.


The customer currently has standard frame relay PVCs on the same link as the new MPLS service and will be migrating from the legacy PVCs to the MPLS environment so I wanted to create a lab that is as close to their environment as possible.


Using the SLA monitor and static route tracking looks like it will get me close enough. I have to jump through a few hoops (static host routes to the CE pointed at the interface, redistribution of static into BGP and then aggregating the route back to /30) but from the CE perspective it looks close enough to what they will expect from their service provider (other than the fact that the PE/CE links will have the aggregate attribute set-not a big deal for the lab environment though).


Thanks for your help.


-Ed-

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