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VPN and BGP selection

I have two routers connected to each other via an eBGP protocol. 

They are also connected by IPSec/GRE ,

I want that IPSec/GRE link to be only used when the eBGP link breaks down.

So under normal circumstances only eBGP should be used.


Can someone advice me please?


IPSec and GRE are dependant

IPSec and GRE are dependant on eBGP for transport right?? A diagram and more info will certainly help.

Definitely need to see a

Definitely need to see a topology on this one. Too many ways this could work or not work.

@Colin_Clark, GRE/IPSec tunnel are not exclusive to eBGP. If the GRE tunnel destination is not known via the eBGP peer, there is no dependency. You can easily imagine how this is possible:

  • Suppose Datacenter1 and Datacenter2 are connected via a L2 WAN service ( say VPLS)
  • Say this is expensive so the OP doesn't want to get to of these. Instead, they have a 100Mbps internet link..they leverage IPSEC/GRE viat the Internet link as intra-datacenter back up link

Then the two routers have an eBGP session. And the tunnel destinations for the GRE tunnel use the back internet link. If this is the OPs setup ( and the eBGP session is established using loopback addresses on the routers), then there is no problem--but I'm not going to bother guessing at what the OPs network is like.

Well aware they are not

Well aware they are not dependent on each other but from the OP description, it very well could be. Some sort of routing will be needed in the transport of the GRE tunnel interfaces, I'm asking if it's eBGP.

@Collin_Clark, Apologies, I



Apologies, I misread your original reply. I thought you were making an affirmative statement and not asking a question.

Cisco Employee

Hi, In case of BGP failure,



In case of BGP failure, how are you pushing traffic over GRE tunnel. Are you running any igp/bgp protocol over GRE tunnel. If it is other than BGP, AD value of that would be lesser than eBGP(AD 20). So when eBGP will fail, route from other routing protocol will get installed. If it is BGP only, you need to play with BGP attribute (like local preference) to prefer one over other.




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