Re: [dhcwg] [EXTERNAL] Question to DHCPv6 Relay Implementors regarding draft-ietf-dhc-dhcpv6-pd-relay-requirements Wed, 07 October 2020 13:54 UTC

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Subject: Re: [dhcwg] [EXTERNAL] Question to DHCPv6 Relay Implementors regarding draft-ietf-dhc-dhcpv6-pd-relay-requirements
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> On 7 Oct 2020, at 15:50, Templin (US), Fred L <> wrote:
> We implement DHCPv6 PD on relays. The relay is always co-resident with the
> delegating server and behaves according to RFC6221. Are we covered?

What's your experience with implementing section 3.5 / R-4?


> Thanks - Fred
> From: dhcwg [] On Behalf Of
> Sent: Wednesday, October 07, 2020 3:26 AM
> To: v6ops list <>rg>;
> Cc: dhcwg <>
> Subject: [EXTERNAL] [dhcwg] Question to DHCPv6 Relay Implementors regarding draft-ietf-dhc-dhcpv6-pd-relay-requirements
> This message was sent from outside of Boeing. Please do not click links or open attachments unless you recognize the sender and know that the content is safe.
> Hi,
> We are currently finishing WGLC for this draft. It describes requirements for a 'DHCPv6 Delegating Relay' - this is a router functioning as the L3 edge and DHCPv6 relay (only) with prefix delegation. This is a common deployment scenario, but RFC3633/8415 only really describes PD using a Delegating Router - i.e the L3 edge also functions as a DHCPv6 server with no relay. When the relay and server functions are performed by separate devices a number of problems with how relays behave have
> been observed, so this document addresses them.
> During WGLC for this, Ole raised a comment related to one of the routing requirements: 
> R-4:    If the relay has learned a route for a delegated prefix via a
>            given interface, and receives traffic on this interface with
>            a destination address within the delegated prefix (that is
>            not an on-link prefix for the relay), then it MUST be
>            dropped.  This is to prevent routing loops.  An ICMPv6 Type
>            1, Code 6 (Destination Unreachable, reject route to
>            destination) error message MAY be sent back to the client.
>            The ICMP policy SHOULD be configurable.
> The problem that this is trying to solve is:
> 3.5.  Forwarding Loops between Client and Relay
>    If the client loses information about a prefix that it is delegated
>    while the lease entry and associated route is still active in the
>    delegating relay, then the relay will forward traffic to the client
>    which the client will return to the relay (which is the client's
>    default gateway (learnt via an RA).  The loop will continue until
>    either the client is successfully reprovisioned via DHCP, or the lease
>    ages out in the relay.
> Ole’s comment: "And I would also be happy if we could have some implementors chime in with a "we are happy and able to implement this requirement”.”
> We would appreciate any feedback on this, especially from anyone with experience implementing DHCPv6 relays with PD.
> Thanks,
> Ian
> Current draft version:
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