Using Bind in a dial on demand environment

nwaltham at my-deja.com nwaltham at my-deja.com
Fri Sep 10 19:34:10 UTC 1999


I run a small network of around 20 computers, they are Windows NT and
Windows 95 clients and a Linux Samba Server. The network is connected
to the internet with a dial on demand isdn link. The windows clients
all have there DNS option set to use the linux server as the DNS
server, and the server is running Bind 8.2.1. I have defined a zone to
allow resolution of the names of the individual computers on the
network, outside addresses are resolved using recursion.

Now the question! What are the settings I can put in /etc/named.conf
which will reduce the amount of DNS traffic on the link so the link is
brought up less frequently. For example I want to cache for the longest
length of time, both succesfull and failed lookups.

The reason is this. There are some programs, such as ICQ which as soon
as they find themselves disconnected start doing DNS lookups, which
brings up the link. I am happy for ICQ to be used, but it shouldn't
bring the link up by itself if its the only thing running, otherwise
the link will stay up all day. However if someone wants to telnet or
ftp to a place, then bringing up the link is fine. I have the
autodialer set to ignore ICQ traffic, so if the link is up, it will go
through fine, but if not, it won't. However, with ICQ doing DNS lookups
to icq when it gets disconnected , and then our server does a
recursion, it brings the link up anyway. ICQ is not the only program
that does this, other chat programs do it too, so I need a generic
solution, and caching lookups as long as I can seems to be the answer.

Thanks in advance,
Nicholas Waltham


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