ISC and Cisco IPv6 relay

David W. Hankins dhankins at
Thu Oct 1 17:54:11 UTC 2009

On Thu, Sep 17, 2009 at 10:00:25AM +1200, Eustace, Glen wrote:
> This turned out to be fairly trivial, but not obvious :(
> I had not configured IPv6 global addresses on the inter-router links.  From the routing perspective, they didn't seem to be needed.  The routers were quite happy using the link-local addresses as the next-hop.  Unfortunately, the dhcp6 relay uses the outbound interfaces IPv6 address and needs it to be global so that the server can send the response to the right relay.

yes, that's correct, if there are multiple routers between the relay
and server, the relay needs a global address somewhere to use as a
source address for the reply to be addressed to.  if global addresses
are very undesirable, you could also do multihop DHCPv6 relays

it doesn't need to be on any specific interface...sounds like a bug
in the relay to me if it refuses to use a valid global address on a
different interface as a source address...

David W. Hankins	"If you don't do it right the first time,
Software Engineer		     you'll just have to do it again."
Internet Systems Consortium, Inc.		-- Jack T. Hankins
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