Pekka Savola <[EMAIL PROTECTED]> writes: > RFC2461 discusses that next-hops must be on-link.
> However, section 8 on redirect basically requires: > - routers know each others' link-local addresses (not an issue from > hosts' perspective, just use routing protocols or other mechanisms) > - hosts are able to verify that the redirect comes from the link-local > address the host is currently using as its next-hop As I recall, routers use LL addresses in RAs for source addresses to avoid aliasing problems. If a router has multiple addresses (and if those addresses change over time, e.g., as a result of renumbering) a host could get confused and think there were (say) two routers on the link when the two were really the same. Having the router just always use its LL address when talking to the host via RAs/redirects avoids a bunch of potential problems. E.g., when a router A sends a redirect saying use router B, and B later sends a redirect saying use router C, the source address B uses in the redirect better be the same one router A used as a target in its redirect or the redirect gets ignored. Note that ensuring this would require two different routers to be in sync with each other, which is a pain at best (no obvious way to do that) if any address could be used. Using LLs avoids unneeded complexity. Thomas -------------------------------------------------------------------- IETF IPng Working Group Mailing List IPng Home Page: http://playground.sun.com/ipng FTP archive: ftp://playground.sun.com/pub/ipng Direct all administrative requests to [EMAIL PROTECTED] --------------------------------------------------------------------
