Kacheong Poon writes: > James Carlson wrote: > > > I suspect that talking to such machines on your local network (when > > you have a routable address yourself) requires special work. > > Otherwise, you'll misidentify the peer as off-link and send your > > replies to a router. (Perhaps it'll still work if there's a matching > > route and the router knows what to do with LLA ... and allows > > one-armed forwarding. More likely, it'll fail.) > > > The RFC states that the above MUST NOT be done.
I know. I'm speculating on what you might need in order to make it work. > > Thus, doing nothing means that windows/mac machines stuck with LLAs > > (for whatever reason) will be accessible only by 'cheating.' The user > > will have to explicitly (manually) configure an address in the LLA > > range on one of the interfaces, and treat it as a regular subnet. > > That might be "good enough" for most debugging purposes. > > > The RFC also states that the above SHOULD NOT be done. So? I don't see how that's relevant for a user trying to support systems with LLAs. Moreover, I don't see how it matters -- the protocols will all work properly, even if the address is chosen in some "non random" fashion. > And > the way a routable address can talk to a LLA is > > Whichever interface is used, if the destination address is in the > 169.254/16 prefix (excluding the address 169.254.255.255, which is > the broadcast address for the Link-Local prefix), then the sender > MUST ARP for the destination address and then send its packet > directly to the destination on the same physical link. Quite obviously, that answer is somewhere between "incomplete" and "unusable." When our system with a global address gets a packet from this LLA system, how can it ever send a reply? The only way it can do so is if it has some sort of special understanding of how to reach LLAs. That "special understanding" can be in the form of a configured address and subnet that make this address reachable, or it can be in the form of hard-coded tweaks to the stack. Without that, though, the usual rules apply: when we try to send a packet, we look up the destination address in the forwarding table first. If we find a route, then that's where we're going to send it. If we don't find one, then it hits the floor. > So if the host has more than one interfaces, I guess it just > means that an ARP MUST be sent to all of them to find out where > the LLA is. I don't know if it is a good idea. But if we need > to support this usage, I guess this is the way to do it... It doesn't matter, because it doesn't work. -- James Carlson, Solaris Networking <[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 _______________________________________________ networking-discuss mailing list [email protected]
