[ILUG] DHCP Server problem - wrong DNS information

[John Hegarty]

Ubuntu 7.04

A problem has started happening recently where some clients pick up an
errant DNS server. Instead of the 192.168.0.254 listed in dhcp.conf they end
up with 192.168.1.1 . However the ip address and router address
(192.168.0.93) on the clients are not affected. Not sure that this is
happening at boot time. I have about 500 users on about 200 desktops but
only half a dozen use an email client - ( usually thunderbird on win XP Pro
) the rest use the web and as we use a proxy server the issue doesn't affect
them. The email client users can swap over to the web but I want to avoid
them having to do so.

Any suggestions on whether this is a server problem or something at the
client end?

The max-lease-time is low as we have a lot of devices (too many perhaps) on
one subnet. Having a long lease time causes the dhcp server to run out of
addresses. Keeping it short has prevented that being an issue. No
significant changes have happened on the network recently. The start of
dhcp.conf reads as follows

authoritative;
>
> subnet 192.168.0.0 netmask 255.255.255.0 {
>     authoritative;
>     range 192.168.0.1 192.168.0.230;
>     max-lease-time 28800;
>     option domain-name "cwc.edu";
>     option domain-name-servers 192.168.0.254;
>     option broadcast-address 192.168.0.255;
>     option routers 192.168.0.93;
>     option subnet-mask 255.255.255.0;
>     deny unknown-clients;
>     if substring( option vendor-class-identifier , 0 , 9 ) = "PXEClient" {
>         filename "/ltsp/i386/pxelinux.0";
>         }
>     else {
>         filename "/ltsp/i386/nbi.img";
>         }
>     option root-path "/opt/ltsp/i386";
>
> host computer1 { hardware ethernet 00:1E:52:1D:B5:F0;  }
>

and so on - long list of mac addresses follow

Thanks

jh