DHCPd problem with PXE/Windows clients - multiple leases

[David Rickard]

Hi,

We've got three DHCP servers on three sites, running the ISC DHCP daemon
on SuSE Linux Enterprise Server 10. We also have Zen for Desktops 7 (SP1
Hotfix 3) on all three sites running on Netware 6.5.

My problem is that when the PC boots, it ends up with two leases - one
for when the PXE runs, and another for when Windows boots! I've attached
an example of what happens, and the leases from the log files of the
server, to show what's happening. In a nutshell, it seems to be related
to the fact that the PXE session doesn't show a UID to the DHCP server,
but Windows does. As a result, DHCPD treats them as two different hosts,
and grants two leases. The only way around this right now is
ridiculously short leases, which results in very chatty workstations and
servers.

I tried the "deny duplicates;" setting in the dhcpd.conf, but that
doesn't seem to have worked. We have just over 50% of the DHCP pool
used, so as a result most PCs work, apart from the last ones on which
start showing 'No free leases' in the log file.

I also tried setting one-lease-per-client, but that made no difference. 

I have duplicated the live setup in a test environment. The setup is
thus (if it matters... it could!)

Two servers, 'core' subnet.
Netware OES Server, TFTP server, PXE server
SLES10 Server, DHCPD

Client PC, different subnet. Core switch configured with IP helper
address of the two servers. The DHCP server will only hand out addresses
to known hosts. 

I have set the IP range to just two addresses. I have two clients, so in
theory, that should be OK, they should both have addresses, whether they
are in PXE mode or Windows. One stays running windows, the other
(actually a virtual PC) gets rebooted. When in windows, it is fine, then
the PXE fails as there are no free leases. If I free the windows lease,
the reverse happens.

Can anybody suggest anything to try and alleviate this problem? I've dug
around on many, many, *many* forums, mailing lists, and everywhere else,
but to no avail. There's a few threads on the dhcp-users list which
kinda go nowhere.

Regards,

(NB: These logs are from an older posting I made some time ago on
novell.support.zenworks.desktop-management.7x.imaging-server.linux, but
they illustrate the exact same problem.)

====================== LOG FILES ============================

PXE Boot
========

Oct 27 11:46:08 ernie dhcpd: DHCPDISCOVER from 00:07:e9:f2:d3:13 via
192.168.200.2
Oct 27 11:46:09 ernie dhcpd: DHCPOFFER on 192.168.200.130 to
00:07:e9:f2:d3:13 via 192.168.200.2
Oct 27 11:46:10 ernie dhcpd: DHCPREQUEST for 192.168.200.130
(192.149.238.50) from 00:07:e9:f2:d3:13 via 192.168.200.2
Oct 27 11:46:10 ernie dhcpd: DHCPACK on 192.168.200.130 to
00:07:e9:f2:d3:13 via 192.168.200.2
Oct 27 11:46:10 ernie dhcpd: DHCPREQUEST for 192.168.200.130
(192.149.238.50) from 00:07:e9:f2:d3:13 via 192.168.200.3
Oct 27 11:46:10 ernie dhcpd: DHCPACK on 192.168.200.130 to
00:07:e9:f2:d3:13 via 192.168.200.3

lease 192.168.200.130 {
  starts 5 2006/10/27 10:46:10;
  ends 5 2006/10/27 10:56:10;
  binding state active;
  next binding state free;
  hardware ethernet 00:07:e9:f2:d3:13;
}
lease 192.168.200.130 {
  starts 5 2006/10/27 10:46:10;
  ends 5 2006/10/27 10:56:10;
  binding state active;
  next binding state free;
  hardware ethernet 00:07:e9:f2:d3:13;
}

Windows Boot
============

Oct 27 11:47:11 ernie dhcpd: DHCPDISCOVER from 00:07:e9:f2:d3:13 via
192.168.200.2
Oct 27 11:47:12 ernie dhcpd: DHCPOFFER on 192.168.200.65 to
00:07:e9:f2:d3:13 (BCUC-6D8215E8EA) via 192.168.200.2
Oct 27 11:47:12 ernie dhcpd: DHCPREQUEST for 192.168.200.65
(192.149.238.50) from 00:07:e9:f2:d3:13 (BCUC-6D8215E8EA) via
192.168.200.2
Oct 27 11:47:12 ernie dhcpd: DHCPACK on 192.168.200.65 to
00:07:e9:f2:d3:13 (BCUC-6D8215E8EA) via 192.168.200.2
Oct 27 11:47:12 ernie dhcpd: DHCPREQUEST for 192.168.200.65
(192.149.238.50) from 00:07:e9:f2:d3:13 (BCUC-6D8215E8EA) via
192.168.200.3
Oct 27 11:47:12 ernie dhcpd: DHCPACK on 192.168.200.65 to
00:07:e9:f2:d3:13 (BCUC-6D8215E8EA) via 192.168.200.3

lease 192.168.200.65 {
  starts 5 2006/10/27 10:47:12;
  ends 5 2006/10/27 10:57:12;
  binding state active;
  next binding state free;
  hardware ethernet 00:07:e9:f2:d3:13;
  uid "\001\000\007\351\362\323\023";
  client-hostname "BCUC-6D8215E8EA";
}
lease 192.168.200.65 {
  starts 5 2006/10/27 10:47:12;
  ends 5 2006/10/27 10:57:12;
  binding state active;
  next binding state free;
  hardware ethernet 00:07:e9:f2:d3:13;
  uid "\001\000\007\351\362\323\023";
  client-hostname "BCUC-6D8215E8EA";
}

--

--

David Rickard
ICT Security Officer
david.rickard at bcuc.ac.uk, 01494 522141 Ext: 3531
Information & Communication Technologies
Buckinghamshire Chilterns University College
Queen Alexandra Road, High Wycombe, BUCKS, HP11 2JZ