Multi site BGP Routing design

Michael K. Smith mksmith at
Sat Jun 6 01:37:02 UTC 2009

On 6/5/09 4:42 PM, "Steve Bertrand" <steve at> wrote:

> Justin Krejci wrote:
>> If the private link between the two sites fails, will BGP allow for us to
>> access the IP subnets at site 2 from site 1 via the internet given that both
>> sites are advertising under the same ASN?
> No, because your router at site 2 will not accept any prefix with its
> own AS in the AS_PATH (which site 1 would be advertising from).
If you're running Cisco with the right IOS it looks like you could use the
'neighbor x.x.x.x allowas-in' command to accept your own AS.  Then you would
just have to set your local route origination so that the appropriate routes
were withdrawn when the backnet link goes down.


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