dhcpd responding to unicast?

Martin Garbe monomartin at opennet-initiative.de
Mon Nov 9 23:17:05 UTC 2015

Hello everybody,

we are operating a mesh network and want to enable DHCPv6 in it. We have
not hierarchical network structure. DHCPv6 should not be flooded in the
network. I see two ways for doing so:

1) Implement DHCPv6 Relay Agents on all nodes. Here a node sends the
DHCPv6 solicit to a neighbor node and this node relays the traffic to
DHCP server via unicast. But here we need a relay service on all nodes.

2) Sending the DHCPv6 solicit message via unicast to DHCP server. Do not
use multicast.

My favorit is way 2). After some tests it looks like ISC dhcpd 4.2.2 is
not supporting this operation mode. I get the log messages in dhcpd:
Solicit message from fe80::5054:ff:fe27:b6ae port 546, transaction ID
Discarding Solicit from fe80::5054:ff:fe27:b6ae; packet sent unicast
(CLIENTID 00:01:00:01:1d:d3:87:19:52:54:00:27:b6:ae)

Or am I missing something here?
I am asking because in RFC3315 there is stated in section 1.1.
Once the client has determined the address of a server, it may under
   some circumstances send messages directly to the server using
Our scenario here is one of these "some circumstances".

Does anybody has information whether unicast-only mode is supported by
ISC dhcpd?


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