DHCP trouble with cable modem

[Tim]

On Mon, 2008-02-04 at 12:14 -0700, Phil Meyer wrote:
> We see this all the time at the office with systems that dual boot.
> The DCHP server will see the Linux network as a different one than the
> XP one, even though the MAC address is the same (of course).

More than the MAC is used, or can be used, to determine what to dole out
using DHCP.

On my network it's just about all Fedora PCs, with FC4 to FC7 currently
in use, and three boxes that came with Windows.  The Windows boxes
supply a uid to the DHCP server, and the automatic/default settings for
dynamic IP address assignment in my DHCP server is more interested in
that than the MAC.  So if the same box reboots with Fedora, it'll get a
different IP if there aren't any rules set to fix IPs to particular
machines (e.g. using MAC or hostnames).

If you look at a couple of examples out of my DHCP server log (see
below), you can see a difference between the first one using Windows,
and the second one using Fedora (the uid field).

lease 192.168.1.194 {
  starts 1 2008/02/04 02:51:17;
  ends 1 2008/02/11 02:51:17;
  binding state active;
  next binding state free;
  hardware ethernet 00:05:1c:19:dd:2f;
  uid "\001\000\005\034\031\335/";
  set ddns-fwd-name = "hp.example.com.";
  set ddns-txt = "31daf65c7640fdf2c0d5e7ee40a9358516";
  set ddns-rev-name = "194.1.168.192.in-addr.arpa.";
  client-hostname "hewie";
}
lease 192.168.1.196 {
  starts 1 2008/02/04 09:21:22;
  ends 1 2008/02/11 09:21:22;
  binding state active;
  next binding state free;
  hardware ethernet 00:e0:18:72:0b:4a;
  set ddns-fwd-name = "bigblack.example.com.";
  set ddns-txt = "0099bea168a9g2ce464ef131ffa46c5f96";
  set ddns-rev-name = "196.1.168.192.in-addr.arpa.";
  client-hostname "bigblack";
}

There is a "duplicates" flag in the server configuration that can alter
this behaviour (whether it'll give out the same IP to something with
differing UIDs, or not).  On my system I avoided the problem of
differing addresses for the same boxes by fixing addresses to certain
boxes, in the DHCP server config, using the MAC data.  That technique
was good enough for my purposes.

-- 
(This computer runs FC7, my others run FC4, FC5 & FC6, in case that's
 important to the thread.)

Don't send private replies to my address, the mailbox is ignored.
I read messages from the public lists.