interesting scenario question

[Kevin Darcy]

olabisid at my-deja.com wrote:

> Hello everyone,
>
> I need some advise on how to tackle a situation I have on hand.

"I send you this file in order to have your advice"?  :-)

(Sorry, I just got a Sircam virus email -- my first! -- on my Solaris box
here, and I'm still amused by it).

> Present scenario:
> 2 office locations, with 1 Pri dns server (bind 4.9.3) and a Slave dns
> server (bind 4.9.3). I have an entry for an enterprise system GATEWAY
> located in one location. Both locations use the gateway to access
> another network.
>
> New scenario:
> A new gateway is to be installed in my 2nd location. So that each
> location has its gateway.
>
> Problem:
> How can I implement a dns entry so that using the same GATEWAY name,
> users in the second location use the new gateway. (pls remember the
> 2nd name server is a slave and I don't want to change that).
>
> I've come across the idea of load balancing/redistribution using an
> entry like
> foo.bar.baz   60 IN A 192.168.1.1
> foo.bar.baz   60 IN A 192.168.1.2
> but this doesn't help, as I want each site to use the same name
> (GATEWAY), but to access different servers everytime.

With BIND 4.9.3, the only *ugly* way I can think of to do this is
maintain separate master zones for "foo.bar.baz" on the nameservers at
the different locations. Kind of an "internally-split DNS". Blech.

With BIND 8 and up, you could probably use the "sortlist" option,
assuming you don't mind that *both* addresses will be returned in
responses, but the order in which those addresses are given will differ
depending on what client is doing the asking. A similar approach would be
to use a "fixed" "rrset-order" option. The slave would serve up the name
in a different order than the master would. But I think sortlist is
preferable here, so that even if a client gets pointed to the wrong
nameserver, it still gets the right sort order. Also, the named.conf
definitions can be identical when using sortlist, which might make
maintenance slightly easier.

With BIND 9, another alternative would be "view", which is basically a
more elegant way to do "split DNS". You'd still have to maintain 2
different master files, but you could host them in the same nameserver
instance.


- Kevin