IPv6 prefix delegation on internal interface

Hi,

I'm running UTM in the following scenario: PPPoE DSL Upstream <-> UTM <-> internal router

My provider Deutsche Telekom provides me with a /56 IPv6 prefix, I would like to be able to delegate a prefix of e.g. /58 to the internal router so that this router is able to use the public IPv6 adresses provided to me (issuing a PD request from the internal router to UTM). Is there a way to implement this?

Otherwise the only solution I can think of is using IPv6 ULA adresses internally up to the UTM and do IPv6 NAT there.

Thanks in advance for your replies, any help appreciated.

Kind regards,

GrafZahl