Subject: Link local address for tunnel interfaces

From: Mukesh Gupta <[email-masked]>
Date: Wed, 02 Oct 2002 09:33:44 -0700

Hi,

Is it required to have a link local address on a tunnel interface. I am
implementing IPv6 in IPv6 tunnels and wanted to know whether I should
install a link local address on the tunnel interface. Is there any
document that talks about this ?

If it is required, how should I calculate a unique link local address ?

regards
Mukesh
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From: Brian Haberman <[email-masked]>
Date: Wed, 02 Oct 2002 13:00:30 -0400

> document that talks about this ?

RFC 2373, Section 2.8 requires that a node recognize itself by
"Its Link-Local Address for each interface".  That would include
any virtual interfaces created by a tunnel.

> If it is required, how should I calculate a unique link local address ?

Appendix A of 2373 discusses creating EUI-64 identifiers which
can be used in the creation of link-local addresses.

Regards,
Brian

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From: Robert Elz <[email-masked]>
Date: Wed, 02 Oct 2002 23:57:19 +0700

Date:        Wed, 02 Oct 2002 09:33:44 -0700
    From:        Mukesh Gupta <[email-masked]>
    Message-ID:  <[email-masked]>

  | Is it required to have a link local address on a tunnel interface. I am
  | implementing IPv6 in IPv6 tunnels and wanted to know whether I should
  | install a link local address on the tunnel interface. Is there any
  | document that talks about this ?

Yes, the addr arch doc requires LL addresses on every interface
(and that includes tunnels).

  | If it is required, how should I calculate a unique link local address ?

However you like I think.   But one common method is to use the underlying
tunnel address to form the IID.   For v6 in v6, you could use the IID of
the underlying v6 interface (or any v6 interface).   Or the low N bits of
that where N is 128 - the prefix length of the tunnel.

kre