Re: Router ID on IPv6-Only

[Tom Beecher <beecher () beecher cc>]

> Is there really such as thing as pure IPV6 only?

Yup.

On Thu, Sep 8, 2022 at 11:32 AM Paul Amaral via NANOG <nanog () nanog org>
wrote:

> Is there really such as thing as pure IPV6 only? I don’t think you will be
> able to run IPV6 for transport without the router locally knowing how to
> handle IPV4, at least not right now as there’s a lot of legacy code.
> Usually IPV6 is enabled longer after IPV4 has been running. With that said,
> can’t you just enable ipv4 and not route it passed the router, then use
> RFC1918 to manually general your 32 bit ID.
>
>
>
> Paul
>
>
>
> *From:* NANOG <nanog-bounces+razor=meganet.net () nanog org> *On Behalf Of *Crist
> Clark
> *Sent:* Thursday, September 8, 2022 1:39 AM
> *To:* nanog () nanog org list <nanog () nanog org>
> *Subject:* Router ID on IPv6-Only
>
>
>
> During some IPv6 numbering discussions at work today, someone had a
> question that I hadn't really considered before. How to choose 32-bit
> router IDs for IPv6-only routers.
>
>
>
> Quick background. We have a requirement to convert a significant portion
> of our network to IPv6-only over the next few years. Previously, I, and
> everyone else on the team, have only ever set up routers in dual-stack
> environments. Choosing a router ID for use in routing protocols just
> followed whatever rules you used for your IPv4 networking. You used the
> same router ID in IPv4 and IPv6.
>
>
>
> Well, now there is no IPv4. But BGP, OSPFv3, and other routing protocols
> still use 32-bit router IDs for IPv6. On the one hand, there are plenty of
> 32-bit numbers to use. Generally speaking, router IDs just need to be
> unique inside of an AS to do their job, but (a) for humans or automation to
> generate them and (b) to easily recognize them, it's convenient to have
> some algorithm or methodology for assigning them.
>
>
>
> Has anyone thought about this or have a good way to do it? We had ideas
> like use bits 32-63 from an interface. Seems like it could work, but also
> could totally break down if we're using >64-bit prefixes for things like
> router-to-router links or pulling router loopbacks out of a common /64.
>
>
>
> Also, various network OS implementations will typically automatically
> choose a router ID from the IPv4 addresses on the router by some algorithm
> (e.g. numerically lowest) if not explicitly configured. Was curious what
> IPv6-only routers do. Haven't had the chance to get on some lab gear or
> GNS3 to just try it and see.