jabley at ca
May 25, 2008, 3:17 AM
Post #2 of 2
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Re: Same AS number from different location
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On 24 May 2008, at 00:08, devang patel wrote:
> Is that okay to use Same AS number for the two different site on
> different
> location?
From the perspective of the rest of the Internet, it will be
indistinguishable from a topologically-distributed AS with interior
connectivity, with a different exit policy in different places. So
yes, it will work.
You should note, though, that in the presence of interior connectivity
(e.g. a circuit directly between the sites) site A would learn routing
information about site B internally, and it would not matter that site
A doesn't hear BGP routes announced to the Internet from site B (in
fact, that would be a feature). If you have no internal connectivity,
you might have to think a little harder about that.
I have seen some people plumb tunnels between their sites to provide
interior-looking connectivity where none actually exists.
I have seen other people not worry so much, and just point default at
transit from each place.
> as well as any good documentation or link or deployment scenario
> where I can
> find the merging of two different AS into one AS?
> As well as what to do if I have an IP addresses as a service provider
> dependent block and want to migrate IP addressing to the IANA
> assigned ip
> addresses?
I seem to think you'll find presentations about AS consolidation in
the NANOG meeting archives, somewhere. But basically you join your
ASes together, start advertising routes from the to-remain AS and drop
the corresponding routes from the going-away AS, with appropriate
pauses for checks and breathing.
To renumber, change the addresses on individual things with
appropriate pauses for DNS TTL expiry. Where changes require
interaction with customers, good luck and be patient (or drive round
and change the config on their routers yourself, or give up waiting
and expect them to get back to you when their net stops working, as
appropriate).
Joe
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