Subject: ND- processing neighbor advertisements

From: Sowmini Varadhan <[email-masked]>
Date: Thu, 2 Dec 1999 16:55:49 -0500 (EST)

RFC 2461, Section 7.2.5 [Page 62-63]  has:

  "[if the entry is not incomplete, and the]... Override flag is clear and the
   supplied link-layer address differs from that in the cache, then one
   of two actions takes place: if the state of the entry is REACHABLE,
   set it to STALE, but do not update the entry in any other way;"

This statement (and the text leading up to it) places no requirement
on the Solicited flag, for the transition from REACHABLE -> STALE
for an NA with Override = 0, when the link-layer address in the 
NA differs from the cached value. 

However, in Appendix C [Page 85-86], the relevant transitions are:

  State           Event                   Action                New state

  REACHABLE       NA, Solicited=1,        -                     STALE
                  Override=0
                  Different link-layer
                  address than cached.
                 :
                 :

  !INCOMPLETE     NA, Solicited=0,        -                     unchanged
                  Override=0

which indicate that the REACHABLE -> STALE  transition has a dependancy
on the Solicited flag.

So, which one is more accurate? Should the Solicited flag also
be considered along with the conditions on Page 62-63 ?

--Sowmini

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From: Richard Draves <[email-masked]>
Date: Thu, 2 Dec 1999 15:53:27 -0800

For what it's worth, here's what MSR IPv6 does:

The situation is:
- you already have an NCE with a link-layer address (the NCE is not
INCOMPLETE).
- you receive a neighbor advertisement for the neighbor but with a different
address in the target link-layer address option.
- the override bit is zero.

Then if the NCE is in the REACHABLE state, we set it to STALE, otherwise the
NCE is not updated in any way.

If the solicited flag is set in this situation, then we log a debugging
event (it shouldn't happen in normal operation) but the value of the
solicited flag doesn't change what happens to the NCE.

Rich

> -----Original Message-----
> From: Sowmini Varadhan [mailto:[email-masked]]
> Sent: Thursday, December 02, 1999 1:56 PM
> To: [email-masked]
> Cc: [email-masked]; [email-masked];
> [email-masked]; [email-masked]
> Subject: ND- processing neighbor advertisements
> 
> 
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>