Option 82 renew/rebind problem

Andre Schubert andre at km3.de
Wed Jul 9 05:35:30 UTC 2008

Hi all,

i have a problem with dynamically assignd IPs
and unicast renew/rebind of clients.

Iam using dhcp-3.0.1 and have the following config:

subnet netmask {
    option subnet-mask;
    option routers;

    allow unknown-clients;

    class "dynamic-known-hosts" {
        match pick-first-value(substring (option agent.remote-id,0,6),substring (local-remote-id,0,6));
        max-lease-time 120;
        lease limit 1;
        if (exists agent.remote-id) {
            set local-remote-id = option agent.remote-id;
        log (info,"dynamic-known-hosts");

    subclass "dynamic-known-hosts" XX:XX:XX:XX:XX:00 { lease limit 2; }
    subclass "dynamic-known-hosts" ff:11:XX:XX:XX:01 { lease limit 3; }
    pool {
        allow members of "dynamic-known-hosts";

I have several CPEs behind cablemodems and want to assign IPs to these CPEs using the agent.remote-id option,
which is set by the relay-agent. If the CPEs are broadcasting their packets(DISCOVER,REQUEST) everything works perfect,
as the relay agent forwards these packets to the dhcp-server.
But i have seen some CPEs that send their packets directly to the dhcp-server asking to renew the lease.
When this happens, the relay agent has no chance to add the agent information to the packets.
I searched through the archives and found the following snipped:

        if (exists agent.remote-id) {
            set local-remote-id = option agent.remote-id;

But doesnt seem to work. If a CPE is booted, then this CPEs will be assigned an IP and everything is perfect.
But when this CPE starts to renew directly to the dhcp-server, then CPE got a DHCPNAK and the according lease
state is changed from active to free.

Did i miss something ?
Could someone point me in the right direction ?

Best regards,
Andre Schubert
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: application/pgp-signature
Size: 189 bytes
Desc: not available
URL: <https://lists.isc.org/pipermail/dhcp-users/attachments/20080709/c8b34ba8/attachment.bin>

More information about the dhcp-users mailing list