Subject: Re: Unnumbered and tunnel interfaces in OSPFv3

From: "Naidu, Venkata" <[email-masked]>
Date: Tue, 7 Sep 2004 11:49:56 -0400

-> > - For OSPFv3 purposes, an unnumbered interface is defined
-> as an interface
-> > with no link-local address (but possibly with site-local or global
-> > addresses).
->
-> It funny but I would have interpreted it to be just the
-> opposite - an interface
-> with a link-local address of one sort or another and no
-> site-local or global
-> addresses.
->
-> >
-> > - Any address on the corresponding node is used for the
-> source/destination
-> > address in protocol packets sent over unnumbered
-> interfaces (as in OSPFv2).
->
-> I don't agree here since I think there still should be a
-> link-local address.
->

  I agree with Acee here. Look at RFC 3513, IPv6 Addressing Architecture
  section 2.1 says:

  . . .

   All interfaces are required to have at least one link-local unicast
   address (see section 2.8 for additional required addresses).  A
   single interface may also have multiple IPv6 addresses of any type
   (unicast, anycast, and multicast) or scope.  Unicast addresses with
   scope greater than link-scope are not needed for interfaces that are
   not used as the origin or destination of any IPv6 packets to or from
   non-neighbors.  This is sometimes convenient for point-to-point
   interfaces.  There is one exception to this addressing model:

  . . .

  The concept of unnumbered is completely re-designed in IPv6. It is
  so beautifully designed using link-local addresses, in such a way that,
  it is generalized for all types of interfaces (point-to-point,
  broadcast etc) alike. Such a generalization is achieved using
  Neighbor Discovery (ND) protocol learning Layer 2 addresses more
  effectively than ARP. Previously, as in IPv4, unnumbered used to
  make sense for point-to-point links only.

  In one line, IPv6 link-local addresses does all the trick.
  There is no need for OSPFv3 to specify unnumbered using IfIndexes
  etc, as in IPv4. In fact, look at the below explanation of IPv4
  unnumbered history tied to OSPFv2, in Fred's words.
  http://www.cs-ipv6.lancs.ac.uk/ipv6/mail-archive/rip/1999-01/0005.html

Venkata.