[lug] DNS configuration question

[Jonathan Briggs]

Elyse Grasso wrote:

>I want to set up the mail/web server machine as a dns server that the 
>machines on the internal network can use to locate and identify each other. I 
>assume that the best thing to do is to set up the server as their primary dns 
>and our ISP's nameservers as secondary and tertiary (to give them access to 
>the rest of the web).
>
Do not set the ISP nameservers as secondary and tertiary.  Instead, use 
your internal DNS server as your only server and set your internal DNS 
server to forward requests to your ISP nameservers.  You want to do this 
because the ISP nameservers are likely to return "no address" for 
reverse lookups for any IP in the private IP space, such as 192.168.0.0, 
10.0.0.0, etc.  If the client gets a "no address" response from any 
nameserver, it will return an error immediately.  This means that if 
your internal DNS server gets slowed down and the ISP answers first, the 
name will not be resolved by the client.

I have another comment to make.  Be sure to install a secondary DNS 
server on your network.  If you ever have to take the primary server 
down for maintence or, heaven forbid, it crashes or the network card 
locks up, your users who've become used to the internal names will yell 
and scream.  A second name server prevents this.

I've done both of these things wrong in the past, so I'm telling you 
from experience here. :-)