On 16 okt 2008, at 16:52, Ralph Droms wrote:
My understanding is (and I would happily have my understanding corrected) that there should *never* be a prefix length associated with address assignment, whether that address comes from DHCPv6, manual address assignment, etc. Prefix length is not an attribute of an address
Well, that would make sense in an architecture like CLNP where traffic between any two hosts initially flows through a router until the router sends a redirect, and routers know host addresses through a host-router "routeing" protocol (ES-IS).
But in the IP architecture, a system knows which other systems it can communicate with directly by virtue of the subnet prefix. For hosts you could argue that they can always send packets to a router, so they don't really have to know whether an address is directly attached to the local subnet. (And in this case redirects are possible with IPv6.) But in the IP architecture, there is no difference in this regard between hosts and routers, so if other hosts don't know a certain address is present on the local subnet, routers also don't know this.
More practically, how do you configure an interface if you don't know the subnet mask? Having the address and the subnet mask become available separately is very inconvenient in this regard.
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