Re: IPv6 link local address generation for P2P interfaces

[Greg Troxel <gdt%ir.bbn.com@localhost>]

  Maybe a naive question: the magic that generates link local addresses for
  IPv6 interfaces does not seem to care about POINTOPOINT interfaces,
  so it creates strange setups like this:

    inet6 fe80::a00:20ff:fe99:fc91%pppoe1 ->  prefixlen 64 scopeid 0xb
  or
    inet6 fe80::a00:20ff:fe99:fc91%gre0 ->  prefixlen 64 scopeid 0x9

  Should it check IFF_POINTOPOINT, generate a destination address too and
  adjust prefixlen?

I don't think it should be making up a destination address.  besides not
thinking the specs say that, how would it ensure that the address was
known by the far side?  When I had a ppp link to work, I had link local
addresses on each end and ran RIPng.  Each side sent multicast and
discovered the other, and then forwarded datagrams via the others link
local address, IIRC.

Why do you think prefixlen should be other than 64?

  I'm trying to understand the setup of pppoe(4) for IPv6. The ipcp6
  negotiation uses the first link local address, including it's
  destination address if not unspecified as initial suggestion for the
  negotiation, which does not make a lot sense to me in the default
  setup.

I would say that it should suggest the local link-local address for the
local side, and not suggest an address for the far side.  But I'm not at
all sure.

Is this special for pppoe, or does all ppp with v6 do this?

When I did ppp, all it took was +ipv6 or something like that in the
configs on both sides and it came up with working link-local addresses,
and then RIPng on both sides, and the attached ethernets on both systems
were routed to each other.

Do you have a provider that will do IPv6 over pppoe?