Hi. Quoting from S5.2:
Next-hop determination for a given unicast destination operates as follows. The sender performs a longest prefix match against the Prefix List to determine whether the packet's destination is on- or off-link. If the destination is on-link, the next-hop address is the same as the packet's destination address. Otherwise, the sender selects a router from the Default Router List (following the rules described in Section 6.3.6). So if there are no routers admitting to be connected to the link and the prefix list is empty (no routers to fill it), what happens here? Presumably the longest prefix match will fail implying that the address is off link. Hence we have to find a router, but there isn't one. What do we do with the packet? With a point-to-point link (like the tunnels) we could just stuff the packet down the link and hand off the decision to the other end. For an isolated multiaccess link the decision is not so simple: Just having our own address doesn't allow us to decide whether any other address is on link, so if the destination is not in the neighbor cache already what do we do? Toss the packet or assume it is on-link? Being able to configure an on-link prefix would solve the problem IMO. Am I missing something here? Regards, elwyn Original Message ================ [S5: Prefix List: Having removed the 'assume it is on link' if no routers, it might be useful to allow a prefix to be inserted into the prefix list by manual configuration when dealing with a single link net.] => Is this really needed? Isn't enough to be able to configure an address given that the next hop determination is based on a longest prefix match? I won't add this unless you see a reason for it. s5.2: It ought to be stated that if the default router list is empty then off-link unicast packets will have to be dropped and an 'unreachable' ICMP message sent.[whether the packet ought to have got as far as the interface processing is a moot point]. => Hmmm. How does this work in the case where the destination address is on the other end of an IPv4 tunnel and there is no default router in the list? This is why the onlink assumption was removed. ---------------------------------------------------------------------------- ------ Elwyn B Davies Routing and Addressing Strategy Prime & IPv6 Core Team Leader CTO Office, Portfolio Integration Solutions Ready Nortel Networks plc Email: [EMAIL PROTECTED] Harlow Laboratories ESN 6-742-5498 London Road, Harlow, Direct Line +44-1279-405498 Essex, CM17 9NA, UK Fax +44-1279-402047 Registered Office: Maidenhead Office Park, Westacott Way, Company No. 3937799 Maidenhead, Berkshire, SSL6 3QH ---------------------------------------------------------------------------- This message may contain information proprietary to Nortel Networks plc so any unauthorised disclosure, copying or distribution of its contents is strictly prohibited. ---------------------------------------------------------------------------- "The Folly is mostly mine" and the opinions are mine and not those of my employer. ============================================================================ ====== -------------------------------------------------------------------- IETF IPv6 working group mailing list [EMAIL PROTECTED] Administrative Requests: https://www1.ietf.org/mailman/listinfo/ipv6 --------------------------------------------------------------------