Strange duplicate lease every min ...

[Sébastien CRAMATTE]

Hello,


Since few days I can observe a strange behaviour in our DHCP server.
I'm working for internet cable provider and this dhcp assign public IP.

I can see dhcp.leases file  that some are renewed each 2mn (see
dhcpd.leases extract below ... I've remove orginal Ip and mac address)
I'm running dhcp 3.0.4 on debian sarge with ldap and paranoid patch.
I've set in dhcpd.conf :

default-lease-time 86400;
maximum-lease-time 604800;
deny-duplicates;
ignore-declines;
ddns-update-style none;
one-lease-per-client on;
server-identifier ip.of.dhcp.relay.server

I've very strange because occur only on few IPs 
All dhcp client are  Windows XP sp2 or Windows Vista

Note that we use a dhcp-relay from a CMTS (router for cable modem)
This is this dhcp relay that add  "option agent.circuit-id" and "option
agent.remote-id"

-----


lease xxx.xxx.xxx.xxx {
  starts 5 2007/07/13 12:25:54;
  ends 6 2007/07/14 12:25:54;
  binding state active;
  next binding state free;
  hardware ethernet 00:00:00:00:00:00;
  uid "\001\000\200Zb\237/";
  option agent.circuit-id 0:0:0:15;
  option agent.remote-id 00:00:00:00:00:00;
}

lease xxx.xxx.xxx.xxx {
  starts 5 2007/07/13 12:25:56;
  ends 6 2007/07/14 12:25:56;
  binding state active;
  next binding state free;
  hardware ethernet 00:00:00:00:00:00;
  uid "\001\000\200Zb\237/";
  option agent.circuit-id 0:0:0:15;
  option agent.remote-id 00:00:00:00:00:00;
}

lease xxx.xxx.xxx.xxx {
  starts 5 2007/07/13 12:25:58;
  ends 6 2007/07/14 12:25:58;
  binding state active;
  next binding state free;
  hardware ethernet 00:00:00:00:00:00;
  uid "\001\000\200Zb\237/";
  option agent.circuit-id 0:0:0:15;
  option agent.remote-id 00:00:00:00:00:00;
}