backup DNS

[Barry Margolin]

In article <cj70br$1i91$1 at sf1.isc.org>,
 cristianobianchi at yahoo.com (Cristiano Bianchi) wrote:

> Hi all,
> 
> I need some clarification and any help would be really great.
> 
> We have a dedicated server with 5 IP addresses (www.theserver.net),
> which we use to host our clients' web sites (we are a web design
> agency). Two of the 5 IP's are used as name servers (ns1.theserver.net
> and ns2.theserver.net).
> 
> I would like to provide additional security to our customers, so that
> if the web server (and therefore name servers) is down for any reason,
> we can direct web users to a mirror server, which we have in our
> office. This server has a dynamic IP address, mapped to a host name
> through the free dyndns.org service and our router port forwarding
> (say: theserver.dyndns.org). We might pay the required fee and map the
> server to www.theserver.co.uk.
> 
> The question is. Is it possible/sensible to add the name server
> ns1.theserver.co.uk and ns2.theserver.co.uk to each of our clients
> domain name registrars, as name server 3 and 4, so that (we hope) they
> should be called when/if the main server is down?

Sure, you can list more than 2 nameservers for a domain (unless your 
registrar is *really* lame).  And it's strongly recommended that not all 
of the nameservers be colocated, to avoid a common point of failure.

Note, however, that these additional can be queried regardless of 
whether servers 1 and 2 are down.  DNS doesn't specify any priority 
order for nameservers, they're all considered equal.

-- 
Barry Margolin, barmar at alum.mit.edu
Arlington, MA
*** PLEASE post questions in newsgroups, not directly to me ***