Subject: Question regarding RFC 2461

From: Lori Napoli <[email-masked]>
Date: Thu, 13 Nov 2003 10:21:13 -0500

I have a question about whether a NA sent to all-nodes multicast address
with the solicited bit ON is valid or invalid.  Here are excerpts from the
RFC.

For destination address in a NA:   For solicited advertisements, the Source
Address of an invoking Neighbor Solicitation or, if the solicitation's
Source Address is the unspecified address, the all-nodes multicast address

This makes it sound like a NA could be sent to the all nodes multicast
address and have the solicited bit ON.

However, here is what is says under the solicited bit:  When set, the S-bit
indicates that the  advertisement was sent in response to a Neighbor
Solicitation from the Destination address. The S-bit is used as a
reachability confirmation for Neighbor  Unreachability Detection.  It MUST
NOT be set in multicast advertisements or in unsolicited unicast
advertisements.

This states the solicited bit MUST NOT be set if the NA is destined for a
multicast address.

Can you please clarify if a NA sent to all-nodes multicast address with
solicited bit ON is considered valid or invalid.  Thanks!

Lori Napoli

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From: Roy Brabson <[email-masked]>
Date: Thu, 13 Nov 2003 10:53:33 -0600

> solicited bit ON is considered valid or invalid.  Thanks!

This is covered in section 7.2.4:

   If the source of the solicitation is the unspecified address, the
   node MUST set the Solicited flag to zero and multicast the
   advertisement to the all-nodes address.  Otherwise, the node MUST set
   the Solicited flag to one and unicast the advertisement to the Source
   Address of the solicitation.

Roy