DHCPREQUESTs and What the Logs Show

Martin McCormick martin at dc.cis.okstate.edu
Fri Feb 11 17:38:52 UTC 2011


Bruce Hudson writes:
> > Feb 10 15:56:53 dh1 dhcpd: DHCPREQUEST for <ip> from <mac> via bce0
> 
>     Without other evidence, I would say that this is a normal DHCP renewal
> request. The initial DISCOVER/REQUEST 4-way handshake is broadcast so the
> servers sees the request via the relay. When renewing, clients unicast the
> requests directly to the server so the GIADDR field is empty and the
> server logs the request "via <interface>".

Thank you. That makes sense.

>     If the slave server is seeing the same requests via a relay then this
> is a different issue altogether. That means client broadcasts are being
> dumped onto the master's network; or some broken relay is forwarding DHCP
> traffic without setting the GIADDR field. Are requests being duplicated;
> once "via bce0" and once via a relay?

	I have not seen that recently but DHCPDISCOVER's will
sometimes show up on one server via the local interface and not
show up at all on the other server or show up with the proper
interface. The condition is intermittent and most traffic we see
is okay, meaning I see the appropriate traffic on both servers,
no "peer holds all free leases" messages and no ringing phones.
>     I suggest you sniff traffic on the server to see what is going on.

	I think that is the only thing that will settle what is
happening once and for all.

Many thanks.



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