Logging DISCOVER for DHCPv6

Ray Soucy rps at maine.edu
Thu Apr 2 08:36:04 UTC 2015

Hi List, I hope it's OK to post here.

I'm hoping someone here can help as I haven't had much luck searching on
this topic.

I need a way to log more information when a host does a DHCPDISCOVER,
specifically I'm looking to log the client DUID as well as things
like agent.circuit-id and dhcp6.client-linklayer-addr.

For example, if I don't have a configuration to hand out an address the
only logging I see is:

Apr  2 08:00:53 hostname dhcpd: Server starting service.
Apr  2 08:02:41 hostname dhcpd: Relay-forward message from
2001:db8:100:820::1 port 547, link address 2001:db8:100:827::1, peer
address fe80::adc9:3fcb:b531:d4fa
Apr  2 08:02:41 hostname dhcpd: Sending Relay-reply to 2001:db8:100:820::1
port 547

This doesn't work for an environment where DHCPv6 is used to only respond
to known hosts with fixed-address6 statements as it makes determining if a
client is unknown difficult.

Is there a configuration directive to trigger a "log" statement for these?
I've tried placing log at the global and subnet6 levels in dhcpd.conf with
no luck.

Another option would be support for an "on_discover" target similar to

If neither is supported, has anyone written a patch to do something
similar?  The goal is to bring DHCPv6 to the same level as DHCP for IPv4
for our in-house IPAM, but the lack of logging is a problem.

I'm testing with a freshly built 4.3.2

Ray Patrick Soucy
Network Engineer
University of Maine System

T: 207-561-3526
F: 207-561-3531

MaineREN, Maine's Research and Education Network
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