Running DHCPv6 relay without interfaces

Peter Rathlev peter at
Thu Mar 14 17:01:58 UTC 2013

On Thu, 2013-03-14 at 11:35 -0400, Neff, Glen wrote:
> Since I've become the list whipping-boy for the day. . . 

The whipping is all in good spirit. :-)

> While correct that a DHCPv6-relay does not have to be a router, I do
> not think it's correct to say a single interface can mean multiple
> broadcast domains.  If there was multiple broadcast domains associated
> with a single NIC, then surely this would be a trunked interface with
> sub-interfaces for each broadcast domain.

But nobody's talking about several broadcast domains. The function of
the relay is to pick up a broadcast/multicast packet and send out a
unicast packet. An IPv4 broadcast packet will only be seen by hosts on
the local LAN, whereas a unicast packet sent to the server address can
traverse several LAN segments on account of being routed.

Putting the router relay function on a router is actually the "special
case" even though it's a very common one.


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