AS and advertisen questions

David Swafford david at
Sun Jun 26 02:11:26 UTC 2011

Yep, we do it that way.

We basically treat each of our datacenter's as their own entity, using
separate space for each, but all with the same AS #.  What Joel
mentioned is going to be the major catch, in that for each of the two
disconnected AS's to accept the opposite sites routes, you'd need to
relax BGP's loop prevention check (which looks for it's own AS #
within the AS Path of incoming routes).

If your on Cisco gear, you'd need to add an additional command under
the BGP neighbor configuration that says "allowas-in".  Here's a breif
doc from Cisco on configuring this


On Sat, Jun 25, 2011 at 9:39 PM, Joel Jaeggli <joelja at> wrote:
> On Jun 25, 2011, at 6:03 PM, Deric Kwok wrote:
>> Hi
>> Can we use same AS to advertise different networks in different location?
>> We would like to use Seattle as production network and New York as testing
>> eg:
>> Seattle: network
>> New York: network and ipv6 network.
>> Thank you
> Assuming you want the two instances to be able talk to each other you just have to relax loop detection so that you will accept prefixes from your AS...

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