North American Network Operators Group

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Re: Multi-home II

  • From: Alex Bligh
  • Date: Sun May 14 12:52:58 2000

> > Can you please help point out a good may to multi-home?
> > I would like to get a site put in a Co-lo in the west coast
> > and one in the east coast.  Both would be different co-lo's.
> > Could I get a single ASN and handle both places with different
> > subnets under the same ASN?

Yes but it's kludgy as your West coast router's BGP loop
detection algorithm will cause it to ignore the routes
to your East coast colo that are heard from your West coast
upstream. You can fix this, for instance, by defaulting
to a network originated by your upstream.
I am assuming you send different subnets to your
upstream(s) at either site; if both subnets together form
a supernet and you use the same upstream, you can also send
that same supernet from both East and West coasts and mark
the subnets no-export which should (a) save on prefixes and
(b) mean your advertized route is larger and less likely
to get filtered / damped.

Note you are not (necessarilly) multihoming here as you have
two instances of one customer ASN - you are multihoming if you
connect one of your sites to more than one upstream. If you
only have one upstream on each coast, you may as well use
static routes and no BGP at all.

Alex Bligh
VP Core Network, Concentric Network Corporation
(formerly GX Networks, Xara Networks)