multihoming without BGP

Dean Gaudet dgaudet-list-nanog at
Wed Jun 11 09:52:47 UTC 1997

On Tue, 10 Jun 1997, Robert E. Seastrom wrote:
> 4) It puts the onus for fail-over on the DNS server, which means one
> is going to be using very short TTL.

Suppose you run two nameds.  One with an addr on provider A, and one
with an addr on provider B.  Each one responds with only the address
from its respective provider.  Suppose A goes down.  Then (most) new
folks won't be able to reach your A name server and so won't even be
trying your A address.  (You have to assume here that your site isn't
popular enough to be in most ISPs caches already... because if it were
that popular you probably can get PI space anyhow.)

This violates the rules of DNS however.  Those nameservers can't claim
to be authoritative and yet yield different answers.  (And Paul is
probably disappointed I'm suggesting it!)

But going to this extreme is probably not even necessary any longer.
MSIE 3 will skip past dead addresses and try all A records.  Netscape
communicator is supposed to do that (I haven't tested).  And Squid will
try all addresses.  That leaves navigator 3.0.  Give it six months.


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