On Tue, Jul 05, 2005 at 06:07:41AM -0400, Ken Raeburn wrote: > On Jul 5, 2005, at 03:07, The Orange Rider wrote: > >It's been suggested to me that this may be for security reasons to > >make sure that the host isn't using a router that has snuck into the > >network, or that it might be used to force a host to choose a certain > >path when presented with equally efficient options on which to send a > >packet, but I thought I'd check what the IPv6 experts have to say. > I'm not an "expert", but those are certainly the first things that come to > mind. (And forget "equally efficient" -- just consider a host with two > network connections, finding a router on each. They may not be "equally > efficient" paths to the Internet at large, but how is the host to know that?) Indeed, that's the main reason for a default gateway. It's your network admin telling you which is the best route, so you don't need a local routing protocol like BGP telling you. If your node is participating in BGP, OSPF or even RIP, you don't need a default gateway, you have enough information to choose one on a per-destination basis. > There're also "non-broadcast multiple access" link layers where router > solicitation might be tricky; I'm not familiar with the details. I think > 6to4 is one such; the IPv4 Internet can be treated as your link layer, but > you can't send a packet to all IPv4 nodes looking for a router. Actually, IPv4 Anycast is supposed to do something like that, except with routing trickery. You send to 192.88.99.1, and IP is supposed to drive your packets to the nearest node that is advertising that address. It's kinda like the ::ff02 (is that right?) routers-on-link IPv6 multicast link you use to solicit routers. I doubt 6to4 does broadcast router solicition, but I expect it does something similar to directed neighbour discovery when given a new link-local destination address (eg another 6to4 address). -- ----------------------------------------------------------- Paul "TBBle" Hampson, MCSE 8th year CompSci/Asian Studies student, ANU The Boss, Bubblesworth Pty Ltd (ABN: 51 095 284 361) Paul.Hampson@Anu.edu.au "No survivors? Then where do the stories come from I wonder?" -- Capt. Jack Sparrow, "Pirates of the Caribbean" This email is licensed to the recipient for non-commercial use, duplication and distribution. -----------------------------------------------------------
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