can't get option 82 data recognized by dhcpd

Ed Ravin eravin at panix.com
Wed Feb 16 15:40:46 UTC 2011


On Wed, Feb 16, 2011 at 09:39:48AM -0500, Adam Moffett wrote:
> >The configuration of the network was such that the server running dhcpd was
> >listening directly to the network where the client was running.
> Out of curiosity is it working now?

Yes, dhcpd is now behaving as expected.

> Someone else recently had difficulty with dhcpd receiving requests
> from both the relay agent and the client at the same time.  I don't
> remember what the result was, but it didn't work the way he
> expected.

One lesson for posterity - the "log" and "execute" statements I inserted
for debugging were ineffective - they were trying to log or display
the circuit-id and remote-id, which did not exist in the received packet.
dhcpd seemed to ignore the log statement, and issued a "bad arg" error
for the execute statement, which only increased my confusion.

If I hit something like this again, I will put in multiple log or
execute statements for debugging - the first one with just the arguments
that I know exist, like the MAC address of the client, and the subsequent
ones for the data I hope exists in the packet.

> Unless they've changed something recently, you may have to do
> something to prevent the dhcp server from receiving the broadcasts
> from the clients directly.

That was the fix - either limit the listening interfaces on the
command line or insert an access list somewhere to block the packets.

	-- Ed



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