One Domain; Multiple IPs.

[Joseph S D Yao]

On Mon, Jul 16, 2001 at 07:12:33AM -0700, Dominik wrote:
> We have one domain, which is mostly used to access a webserver.  The
> webserver has two Internet connections; when one goes down, it can
> still be accessed via the other.  Obviously, this server has two IPs
> (one on each connection).  Unfortunately, www.domain on this box can
> only resolve to one IP, as far as I know.  Is there any way to specify
> two addresses, so that when one connection goes down, the nameserver
> automatically starts responding with the IP for the other connection?
> 
> I realize that there probably isn't any way to do this with standard
> BIND.  One thing I was wondering about--how would NetSol react if we
> submitted two nameservers for our domain, with each one responding to
> the www.domain with a different IP?  Is this a solution in any way?

You could have two name servers, giving out different IP addresses.
That way, if one side goes down, only HALF the accesses would be to the
dead IP address.

You could put multiple IP addresses in all of your name servers.  With
the same result.

It sounds like you want to have your connection working whether one ISP
has gone down or not.  The best way is probably to have a single IP
address behind a router with connections to BOTH ISPs.  Arrange with
both ISPs to allow your router to broadcast your IP address vis OSPF to
the ISPs' router networks.  Only the really good ISPs - or the really
small ones - might allow this, especialy since your IP address will be
from only one of the two ISPs!  But this means that your users will
never be served a dead IP address, unless the lines from both ISPs are
down.  And if that happens, you'll probably be digging the site out
anyway.

-- 
Joe Yao				jsdy at cospo.osis.gov - Joseph S. D. Yao
OSIS Center Computer Support					EMT-B
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