DHCPD dying..

[Aaron Grewell]

> -----Original Message-----
> From: linux-users-bounces at linux-sxs.org 
> [mailto:linux-users-bounces at linux-sxs.org] On Behalf Of 
> Matthew Carpenter
> Sent: Tuesday, November 30, 2004 4:41 AM
> To: Linux tips and tricks
> Subject: DHCPD dying..
> 
> I have seen DHCPd die a couple times over the last week on a 
> customer's site.  The messages seen after rebooting the 
> system (this was their attempt to troubleshoot before calling 
> me) are as follows.  The one that catches me off guard is at 
> 7:59:21 (Not Authoritative?), although that is not the last 
> message before dying.  At the end it looks like DHCPd 
> restarted (although I'm not sure why) and perhaps found 
> another DHCP server on the network?  Or does that mean there 
> is another DHCP server running on that box?
>

What you're seeing in the logs is a combination of 2 things.
1) There's another DHCP server running on your subnet.  Since DHCP is
broadcast-based that's a bad thing.  I'd recommend waiting 'til after hours,
dropping the official DHCP server, and then doing a release-renew on a
client.  On a Windows-based client, 'ipconfig /all' will tell you all about
your configuration, including the IP address of the DHCP server that gave
the client its IP.  There are other ways to find an unauthorized DHCP
server, but that's probably the quickest.  You'll probably find that some
doofus either set up a server 'for test reasons' or (even more likely)
installed their own WAP or other hardware device that has its own DHCP
server.

2) You haven't defined your DHCP server as 'Authoritative' for the subnets
it serves.  That means that while it will hand out DHCP addresses, it will
not send out 'DHCPNAK' packets to clients whose requests conflict.  If this
is your official DHCP server, you need to set it as Authoritative for the
subnets it serves.  Don't do it until you've tracked down your unauthorized
server, however, or you'll hose a bunch of your clients.  They'll get those
'DHCPNAK' packets and then they won't get IP's.  All this is explained much
more fully in 'The DHCP Handbook' which I highly recommend if you're going
to spend much time with ISC DHCP.

HTH,
-Aaron