DHCP assigns 2 IP's to 1 mac address..

Question

hopefully someone can help me.

I have a DHCPD/PXE Server that seems to be assigning 2 IP addresses for the same mac address.

I need computers getting assigned ip addresses to be sequential

I have tried "allow duplicates;" and "deny duplicates;" I can see the ONLY difference is this "uid" line.

Other than this annoyance -- my dhcpd/pxe server works fine.

Heres a snippet from my Leases File:

lease 10.11.46.227 {
  starts 4 2014/10/02 15:01:06;
  ends 0 2150/11/08 21:29:20;
  cltt 4 2014/10/02 15:01:06;
  binding state active;
  next binding state free;
  hardware ethernet 00:1e:67:b9:32:f6;
  uid "\000\215\013\011b\345\227\021\343\270\270\000\036g\2712\366";
}
lease 10.11.46.228 {
  starts 4 2014/10/02 15:09:13;
  ends 0 2150/11/08 21:37:27;
  cltt 4 2014/10/02 15:09:13;
  binding state active;
  next binding state free;
  hardware ethernet 00:1e:67:b9:32:f6;
}

Here is my dhcpd.conf

    allow booting;
    allow bootp;
    authoritive;
    deny duplicates;

    class "pxeclients" {
            match if substring(option vendor-class-identifier,0,9) = "PXEClient";
            next-server 10.11.0.1;
            filename "pxelinux.0";
    }

    subnet 10.11.0.0 netmask 255.255.0.0 {
            range 10.11.1.1 10.11.25.200;
            default-lease-time 4294967294;
            max-lease-time 4294967294;
            min-lease-time 4294967294;
    }

    # Pxe Server so it doesnt get changed.
    host masterPXE {
            hardware ethernet 00:1E:67:98:D5:EB;
            fixed-address 10.11.0.1;
    }

You have two DHCP clients (Maybe netboot and the actual OS) on the same machine, reporting different ID strings. So the server sees a new lease request, not a renewal. — Ben Voigt, Oct 02 '14 at 21:59

score 0 · Accepted Answer · answered Oct 02 '14 at 23:29

I've seen this with linux systems that have ip=dhcp enabled in kernel options and then a secondary dhcp client that runs in userland that re-requests an IP address.

The easiest solution is to just set your max-lease-time to something small like 5 minutes, or remove the dhcp host id from the user-land client so that it looks like the client is just asking for another DHCP address when it already has one.

DHCP assigns 2 IP's to 1 mac address..

1 Answers1