Running DHCPv6 relay without interfaces

Chris Buxton clists at
Thu Mar 14 17:10:19 UTC 2013

On Mar 14, 2013, at 6:40 AM, Peter Rathlev wrote:

> On Thu, 2013-03-14 at 08:56 -0400, Neff, Glen wrote:
>> This makes no sense.  If you don't have multiple interfaces, then you
>> shouldn't need a relay.
> I disagree that relay with only one interface doesn't make sense. If the
> DHCP server is not connected to the local LAN you need something to
> forward the requests. The relay agent just receives a broadcast (or
> multicast for IPv6) packet and converts it to a unicast packet.
> For DHCPv6 you could also route the FF02::1:2 address to the DHCP server
> but that would require L3 multicast routing.

I believe the correct address for site-wide routing of the request would be FF05::1:2, not FF02::1:2. Multicast routing is something that should be implemented in an IPv6 world.

Another option would be to join the entire site into a single IPv6 vlan (separate from the smaller IPv4 vlans) and put the DHCPv6 server directly on that vlan. No broadcast can mean larger vlans in an IPv6 world.

Chris Buxton
BlueCat Networks

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