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Re: How Not to Multihome
- From: Patrick W. Gilmore
- Date: Mon Oct 08 21:27:53 2007
On Oct 8, 2007, at 6:19 PM, Justin M. Streiner wrote:
On Mon, 8 Oct 2007, [email protected] wrote:
That brings up an interesing point. My biggest fear was that one
of my
other customers could possible be closer to me that the ISP that
provides
the primary link and it would cause them to favor the backup link
because
of AS path. I think they are going to fight me on this and
telling them
to multihome to their original ISP would probably be frowned upon
at this
point. I was hoping that there was an RFC for multihoming that I
could
use to bail myself out.
If you went ahead and did this, the more specific route being
announced by you on behalf of your customer would be more likely to
attract traffic back to you. Prefix length is checked in the BGP
route selection process before AS path length. This would work in
normal "everything works fine" situations, but when things break,
troubleshooting the source of the customer's reachabilit woes will
get very interesting.
You have made an assumption that the original upstream would not
originate a prefix equivalent to the one you are originating.
--
TTFN,
patrick
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