Subject: Re: ipv6 over PPP
To: Greg Troxel <>
From: Robert Elz <kre@munnari.OZ.AU>
List: tech-net
Date: 09/25/2003 20:20:05
    Date:        25 Sep 2003 08:44:25 -0400
    From:        Greg Troxel <>
    Message-ID:  <>

  | I do v6 over PPP, but both sides are routers.

Yes, that's essentially what I want as well.

  | I have addresses assigned on an Ethernet on the dialing side,

That's what I would prefer to avoid - I want all of the flexibility of
a typical IPv4 dialup PPP user.

  | So, I only have link-local addresses assigned, and this all works fine
  | - I had no difficulties.  I realize this isn't what you are trying to
  | do.

Actually, that would be fine - I need no global addresses on the PPP link
itself (I probably would prefer them, I prefer numbered over unnumbered
links, but that is a minor point).

The question is how I get the address(es) for the ethernet(s) without
manually configuring them, because they're really not going to be stable.

  | Or, rtadvd should be fixed to cope with interfaces coming and going.

Yes, that's the other option - but even there it still needs a way to
be told to avoid some particular interfaces (or, as it is now, to use
some particular interfaces).   The mere existence of an interface doesn't
mean that I necessarily want to send RA's at it, even if I am a router.

Whether it is better to list the interfaces to use, or those not to use,
or some ugly combination, will end up very much depending upon the
anticipated usage pattern, and so won't necessarily be the same for

  | Ah - if you have a router, you should be running a routing protocol.

Yes, can do, but not until after I get some address to advertise.

  | But, you want a dynamic prefix - presumably copied somehow to the
  | other interfaces, so perhaps you are really feeling pain from the lack
  | of router renumbering.

No, router renumbering doesn't help (wouldn't help).   As its name
implies, it is "re"-numbering - it only really works if you have an
address to start with (and the LL address isn't really good enough,
though I guess a very perverse configuration might be made to work).

I am feeling the pain from the lack of any kind of initial configuration
protocol - but particularly so in this case, as a similar system running
a typical IPv4 configuration "just works".   IPv6 isn't supposed to lack
functionality that IPv4 provides.

Dialup PPP is one blatant case where such a protocol is needed.

  | My PPP dialup is static - I only dial into one place.  So I just
  | allocated prefixes and had no trouble.

That's what I am doing short term, but it isn't the answer.

  | I am not aware of any implementations of router renumbering (RFC2894).

KAME has one, but it is disabled in their releases (they implemented
the protocol in its barest form, ignoring security, and what's more,
stability: renumber, then reboot, and the renumbering vanishes).

(Also, the kernel has changes since their implementation so half the
work is now missing - code  that used to be in the kernel needs to be
moved to userspace - I have an implementation where that's been done

  | The v6 wg lists "Proxy Router Advertisement" as a work item, to be
  | completed by July 2003, but I can't find any drafts or RFCs about it.

I'm not entirely clear what that refers to, but I suspect that it isn't
anything that would be helpful here.    (The v6 WG has gone off the rails
in the last year anyway - more or less since Deering vanished - though his
year in the wilderness must be just about up now, just maybe he'll return
and help get that wg doing something productive again).

I suspect that what's really needed here (for this particular problem, and
not router configuration in general) would come from the ppp wg (if it
survives) though.