[c-nsp] automating router failover in eBGP environment

[Chuck Church]

Since the customer is homed to two different providers they most likely have
their own AS number.  So the right way would be have each router do eBGP to
one of the providers, and iBGP between the two routers.  Each router should
announce the customer's IP space to the provider.  BGP timers can be
adjusted down to a reasonable amount, maybe 20 seconds.  There are other
options like BFD to help as well.   HSRP will work on the inside, but not on
the outside, since it's doubtful the two WAN providers are sharing the same
subnet.

Chuck

-----Original Message-----
From: cisco-nsp-bounces at puck.nether.net
[mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of Adam Greene
Sent: Wednesday, March 13, 2013 5:55 PM
To: cisco-nsp at puck.nether.net
Subject: [c-nsp] automating router failover in eBGP environment

Hi guys,

 

Customer has a 7204VXR (15.1(4)M5, Advanced Enterprise K9) running eBGP to
two upstream providers on the WAN side, and to about 10 customers on the LAN
side. The (2) WAN ports and the (1) LAN port are all GigE. They have a
redundant 7204VXR they can manually fail over to when the primary router
fails. 

 

They want to automate the failover.

 

My first thought is to put a switch in front of and behind the two 7204VXR's
and run HSRP, on both the LAN and WAN interfaces of the routers. 

 

Questions: 

-          Will I run into any gotchas with this approach; and 

-          Is there a better way?

 

Convergence is a big issue. It needs to be as fast as possible. I assume BGP
peering will pass to the backup router as fast as HSRP does, since all the
BGP peers care about is the IP address they are peering with, and the
virtual IP will not change during failover.

 

But maybe there is a better / faster way.

 

Thanks for any input / advice.

 

Thanks,

Adam

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