For example,an interface has two an addresses, automatic-configured 1000::1/65
and manually-configured 2000::1/64,and 1000::2/64 is the on-link neighbour of
the interface.We send a packet, for example and ICMPv6 echo, with a destination
address of 1000::2 from the interface,then the source address would be
2000::1because it is manually-configured.Then the destination address of the
ICMPv6 echo reply would be 2000::1,in the worse case,the sender of the ICMPv6
echo reply does not have a route to 2000::0/64.The sender of ICMPv6 echo would
not receive an echo reply, though it had sent a packet to it's on-link
neighbour.
The mainly porpuse of source address is two-way communication,it has nothing to
do with the way it is configured.
----- Original Message -----
From: "James Carlson" <[EMAIL PROTECTED]>
To: <ipv6@ietf.org>
Sent: Wednesday, October 25, 2006 3:52 AM
Subject: address selection and DHCPv6
> I've done quite a bit of searching over the archives and over various
> web resources, but I haven't seen this issue addressed directly.
> Apologies if I've just missed it.
>
> RFC 3484 ("Default Address Selection for Internet Protocol version 6
> (IPv6)") section 5 gives a set of ordered comparisons for source
> address selection. However, missing from this list is a distinction
> implied by RFCs 2461 and 2462: some systems may have a mix of
> addresses acquired by stateless address autoconfiguration, stateful
> (DHCPv6) configuration, and manual addressing. How are these
> distinguished?
>
> Rule 7 does address the temporary (RFC 3041) addresses, but what about
> these other flavors of addresses? Are they distinguished only by
> scope?
>
> Was this issue addressed and intentionally omitted from the RFC? (If
> so, I don't see it in the archives.)
>
> I suspect that some clients may need to distinguish among the various
> flavors here. I'd suggest amending Rule 7 to read:
>
> Rule 7: Prefer stable, public addresses.
> If SA is a manually-configured address and SB is automatic or
> temporary, then prefer SA. If SA is automatically configured via
> stateful (DHCPv6) methods and SB is automatically configured via
> stateless methods or temporary, then prefer SA. If SA is
> automatically configured via stateless methods and SB is temporary,
> prefer SA.
>
> Similarly, if SB is a manually-configured address and SA is not,
> then prefer SB. If SB is stateful and SA is stateless or
> temporary, prefer SB. If SB is stateless and SA is temporary,
> prefer SB.
>
> When the application has the "prefer temporary address" flag
> enabled, all temporary addresses are (within this rule) elevated in
> preference above manually-configured addresses. The other
> preferences are unaltered. (In other words, the preference order
> with this flag set becomes temporary first, then manual, stateful,
> and stateless last.)
>
> ... or, to simplify, defining a "stability_of_address(A)" function
> that can work here.
>
> --
> James Carlson, KISS Network <[EMAIL PROTECTED]>
> Sun Microsystems / 1 Network Drive 71.232W Vox +1 781 442 2084
> MS UBUR02-212 / Burlington MA 01803-2757 42.496N Fax +1 781 442 1677
>
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