Preserving /etc/resolv.conf when dialup connection is active

[David Garamond <lists@zara.6.isreserved.com>]

Everytime I connect to the Internet, the 'nameserver' entries which are 
originally in /etc/resolv.conf are replaced with the ones from the 
dialup connection (they are restored after I hang up).

How to prevent this? I want to preserve 'nameserver 127.0.0.1' since I 
serve some intranet zones on my computer.

Regards,
dave