How Not to Multihome

Tue Oct 9 02:37:34 UTC 2007

On Mon, 8 Oct 2007, Patrick W. Gilmore wrote:

:To be clear, I am not suggesting de-aggregating every CIDR down to /
:24s.  But the global table doesn't grow any more whether the customer
:announces the /24 from their own ASN, or if you muti-originate it
:from two upstreams - or just one upstream for that matter.  So there
:is no "legitimate reason" to _not_ announce it, but there is a reason
:to announce it.

Bingo.

And, I'd hazard to guess that many readers of this thread have broken more
than a single unwritten rule.  I recall being chastised relentlessly years
back for doing ibgp over a gre tunnel as I saved up for a real trunk.
Guess what - it worked wonders in the short term (though I'll admit I'm
embarrassed to rehash it).

Bottom line (getting back to the original question) is yes, it's ok, so
long as you handle due diligence with the "owner" of the cidr space.  RFC,
no, courtesy among peers, yup.

cheers,
brian