option82 "agent.remote-id " is missed in some lease ... Why ?

Glenn Satchell Glenn.Satchell at uniq.com.au
Wed Oct 25 13:05:54 UTC 2006

>Date: Wed, 25 Oct 2006 11:21:54 +0200
>From: Sébastien CRAMATTE <s.cramatte at wanadoo.fr>
>To: dhcp-users at isc.org
>Subject: option82 "agent.remote-id " is missed in some lease ... Why ?
>I've setup cable modem + arris c3 cmts with dhcp 3.0.4
>My cmts act as a dhcp relay and add  option82 to each  CPE leases ...
>It's very strange because some lease have  "agent.remote-id "  line (the
>modem mac address added by option82)  and someone  doesn't  have it ...
>All this leases come from the CMTS relay ... so I should have 
>agent.remote-id line for each lease  ?
>Anyone have an idea ?

Any broadcast requests, such as DHCPDISCOVER will be forwarded by the
relay, but once the client has a lease it uses unicast requests direct
to the dhcp server to renew the lease. The dhcp relay is not used with
these, so it has no chance to add its remote id option.

There is a setting you can add to dhcpd.conf to store the agent options
on the lease so that they will be there for renews:

       stash-agent-options flag;

       If the stash-agent-options parameter is true for  a  given
       client, the server will record the relay agent information
       options sent during the client's initial DHCPREQUEST  mes-
       sage when the client was in the SELECTING state and behave
       as if those options are included in all subsequent DHCPRE-
       QUEST  messages  sent  in the RENEWING state.   This works
       around a problem with  relay  agent  information  options,
       which  is that they usually not appear in DHCPREQUEST mes-
       sages sent by the client in the  RENEWING  state,  because
       such  messages  are unicast directly to the server and not
       sent through a relay agent.

Glenn Satchell     mailto:glenn.satchell at uniq.com.au | Some days we are
Uniq Advances Pty Ltd         http://www.uniq.com.au | the flies;  some
PO Box 70 Paddington NSW Australia 2021              | days we  are the
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