Templin, Fred L wrote:
The presence of default routes means that the host should
accept packets from all four routers equally, i.e., and not
only accept the ones from R1 and R2 while dropping those
from R3 and R4, right?
What do you mean by "accept"? The content of the default router list (or
a routing table in general) doesn't have any impact on what received
packets are accepted by a host.
I mean that on some link types hosts need to be careful
about what routers they accept packets from, and should
not accept packets from a node pretending to be a router.
That might make sense in some cases. (But more typically it is routers
and other network devices like bridges that might want to verify source
addresses etc.)
But I don't see what that has to do with RFC 4191.
Some routing protocols declare a link down when a certain
number of hello messages are lost. I don't see why NUD
could not be used in the same way.
Perhaps because NUD is *NOT* a Hello protocol.
With enough thrust pigs can be made to fly, but that doesn't mean it is
a good idea.
The closest thing we have to a hello protocol in ND are the periodic
RAs. And when the default router lifetime from the RAs time out, then
the default route, as well as any more specific routes from that router,
will time out.
Erik
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