<div dir="ltr"><br><div class="gmail_extra"><br><div class="gmail_quote">On Mon, Jul 24, 2017 at 3:42 PM, Brian E Carpenter <span dir="ltr"><<a href="mailto:brian.e.carpenter@gmail.com" target="_blank">brian.e.carpenter@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">On 25/07/2017 05:46, David Farmer wrote:<br>
> In practice Neighbor Discovery, and other critical protocols, need<br>
> link-local addresses to talk to other link-local addresses and some<br>
> multicast addresses.<br>
><br>
> Also, in theory a link-local address could talk to a GUA or ULA address on<br>
> the same link. However, in practices does this really happen? If it does<br>
> happen in practice what are circumstances?<br>
<br>
I assume you mean a case where the global scope address matches an<br>
on-link prefix? Otherwise the packet is doomed anyway, since no<br>
conforming router will forward it off-link. That doesn't need an ACL.<br>
<br>
Also you must mean a case where RFC6724 is overridden, since otherwise<br>
source address selection will prevent it happening (see the examples<br>
in RFC6724 section 10).<br>
<br>
So, I'm not aware of any realistic case where this happens, or any<br>
reason for it. Or any harm that it would do, for an on-link prefix.<br>
<span class="gmail-m_2967397782224891509HOEnZb"><font color="#888888"><br>
Brian<br>
</font></span></blockquote></div><br>So, the nice summary in the link Gert sent, says; </div><div class="gmail_extra"><br></div><div class="gmail_extra">Neighbor Solicitation (NS) Message</div><div class="gmail_extra"><br></div><div class="gmail_extra">NS is ICMPv6 Type 135 and Code 0</div><div class="gmail_extra">Source address of the IPv6 Packet encapsulating the NS can be one of the two</div><div class="gmail_extra">1. IPv6 address of the originating interface</div><div class="gmail_extra">2. Unspecified address ::/0 (All Zeros) if the NS is sent for Duplicate Address Detection</div><div class="gmail_extra">The destination address of NS can be one of the two</div><div class="gmail_extra">1. Solicited-Node Multicast Address corresponding to the the target address</div><div class="gmail_extra">2. The Target address itself</div><div class="gmail_extra">note: Target address is the IPv6 address of the target of the solicitation and is never a multicast address.</div><div class="gmail_extra">Options Field of the NS can contain the link-layer address of the interface originating the NS <br clear="all"><div><br></div><div>I think that means the Target address, and therefore the destination address of the packet, could be a Link-Local, GUA, or ULA address, and the source of the packet could be a Link-local address. When would a Neighbor Solicitations not using the Solicited-Node Multicast Address normally occur? </div><div><br></div><div>Thanks.</div><div><br></div><div> </div><div><br></div>-- <br><div class="gmail-m_2967397782224891509gmail_signature">==============================<wbr>=================<br>David Farmer <a href="mailto:Email%3Afarmer@umn.edu" target="_blank">Email:farmer@umn.edu</a><br>Networking & Telecommunication Services<br>Office of Information Technology<br>University of Minnesota <br>2218 University Ave SE Phone: <a href="tel:(612)%20626-0815" value="+16126260815" target="_blank">612-626-0815</a><br>Minneapolis, MN 55414-3029 Cell: <a href="tel:(612)%20812-9952" value="+16128129952" target="_blank">612-812-9952</a><br>==============================<wbr>================= </div>
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