I have a question about on-link determination for IPv6 ND.
(RFC2461(bis), Section 2.1) has the following definition
for on-link:
"on-link - an address that is assigned to an interface on a
specified link. A node considers an address to be on-
link if:
- it is covered by one of the link's prefixes, or
- a neighboring router specifies the address as
the target of a Redirect message, or
- a Neighbor Advertisement message is received for
the (target) address, or
- any Neighbor Discovery message is received from
the address."
Clauses 1 and 2 seem to be the same considerations as for IPv4,
but clauses 3 and 4 seem to imply that IPv6 ND implementations
"snoop" on ND messages and "remember" the addresses of neighbors
heard from on the link, e.g., even for multicast ND messages that
are unsolicited or in response to a third party's solicitations.
This is independent of any prefixes assigned on an interface and
also seems to be independent of any neighbor cache entries, since
receipt of ND messages does not necessarily result in neighbor
cache entries being created.
So my question is, for how long will an implementation remember
the addresses of on-link neighbors discovered from snooping on
ND messages - forever? (The spec doesn't seem to provide guidance
on this?) And, what happens when a neighbor that was previously
on-link departs? Will the node try indefinitely to reach the
now-departed neighbor on the local link even if more up-to-date
information is received, e.g., from a routing protocol? The spec
seems to be ambiguous on these points - am I missing something?
Fred
[EMAIL PROTECTED]
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