failover on the internet

Unanswered Question
Aug 25th, 2009
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please find enclosed the diagram, provided by our ISP

we are setting up a second link for the internet failover

looking at the diagram i have questions with the switch failover

if the 2960 switch of the active path fails then

HSRP failover happens. the backup router becomes active.

backup router becomes active and all traffic goes via backup router

IBGP between the primary and backup router fails

so if i am browsing internet and the failover happens, the traffic goes via backup router. what happens to the return traffic? ISP router on the top doesnt know anything about the switch failover. on the internet the return path will still be via the original primary path. the return packets can be dropped once they reach the original primary 2811 router.

what design changes can be made to fix this? or any configuration?


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Joseph W. Doherty Tue, 08/25/2009 - 03:42
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Your diagram also shows eBGP between your site and the ISP. How is eBGP being used? It's possible, with failure of a 2960 switch, the connected 2811 withdraws your internal network(s) from eBGP. If so, the ISP would "know" your internal network can no longer be reached via that path.


BTW, there are other physical topology options that you might consider. For instance, if the connection to the ISPs are copper, you could connect them to the the 2960s and then connect the 2811s to both 2960s.


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