On Mon, Jul 24, 2017 at 3:42 PM, Brian E Carpenter < [email protected]> wrote:
> On 25/07/2017 05:46, David Farmer wrote: > > In practice Neighbor Discovery, and other critical protocols, need > > link-local addresses to talk to other link-local addresses and some > > multicast addresses. > > > > Also, in theory a link-local address could talk to a GUA or ULA address > on > > the same link. However, in practices does this really happen? If it does > > happen in practice what are circumstances? > > I assume you mean a case where the global scope address matches an > on-link prefix? Otherwise the packet is doomed anyway, since no > conforming router will forward it off-link. That doesn't need an ACL. > > Also you must mean a case where RFC6724 is overridden, since otherwise > source address selection will prevent it happening (see the examples > in RFC6724 section 10). > > So, I'm not aware of any realistic case where this happens, or any > reason for it. Or any harm that it would do, for an on-link prefix. > > Brian > So, the nice summary in the link Gert sent, says; Neighbor Solicitation (NS) Message NS is ICMPv6 Type 135 and Code 0 Source address of the IPv6 Packet encapsulating the NS can be one of the two 1. IPv6 address of the originating interface 2. Unspecified address ::/0 (All Zeros) if the NS is sent for Duplicate Address Detection The destination address of NS can be one of the two 1. Solicited-Node Multicast Address corresponding to the the target address 2. The Target address itself note: Target address is the IPv6 address of the target of the solicitation and is never a multicast address. Options Field of the NS can contain the link-layer address of the interface originating the NS 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? Thanks. -- =============================================== David Farmer Email:[email protected] Networking & Telecommunication Services Office of Information Technology University of Minnesota 2218 University Ave SE Phone: 612-626-0815 <(612)%20626-0815> Minneapolis, MN 55414-3029 Cell: 612-812-9952 <(612)%20812-9952> ===============================================
