Stephen Sprunk writes:
Standard practice is to connect all customers in a given area (or signed up
in a given period) to a single concentrator via some sort of virtual circuit
(PPPoE, ATM, FR, etc). This concentrator then internally bridges all of
these virtual circuits into a single subnet with a single prefix, giving you
one route for N customers. OTOH, if you assign a prefix to each customer,
you then have between N+1 and 2N routes for N customers. The latter might
be justified if we're truly committed to eliminating NATs, but it costs a
lot more in routes, in administration, and in address waste (assigning a /48
to what is, in nearly all cases, 1-4 hosts).
Huh? Why wouldn't these prefixes summarized at the
first hop router? And even the first hop router
needs to have routes to get to the last mile, so
whether you do it with an arp cache, SID binding,
or routing table seems like a rather minor
difference in kind.