On Mar 19, 2012, at 11:55 AM, Sabahattin Gucukoglu wrote: > I've obviously not been doing all my homework, and RFC 4007 slipped my attention. Worse, for all the communication my IPv6 nodes are doing amongst themselves using link-local addresses, it's never really been much more than a hastily-justified curiosity why, when I ping one from the other using link-local-scoped addresses, I have to put in this zone identifier (%ifname on BSD and Linux). To be honest, I'm still not sure I understand the argument for a zone identifier. >From MIF's perspective, if the same prefix is placed on multiple interfaces, the system might see peers using a given address on multiple interfaces, and at least some devices might be expected to route between the interfaces. Architecturally, this can be easy to solve or hard. We have any number of cases (think about PPP for example) in which we bundle multiple interfaces under a common super-interface and "do something". In PPP Multilink, we might segment messages into smaller frames, distribute them across a number of interfaces to the same place, and reconstitute the original message on the other side. In this case, it seems that we want IP to use two layers of interfaces, a virtual one instantiated by multiple lower layer interfaces, and place the prefix on the virtual interface. When we are wondering what MAC address should be associated with a given IP address, we ask each of the lower layer interfaces, and if we get a result on one of them we know where we're going. The big issue will be routing among the physical interfaces - something required for it to be seamless and yet not as trivial as it might sound.