Thus spake "Keith Moore" <moore@cs.utk.edu> > > Today, dial-up concentrators usually have an address > > range that it used to assign addresses to people that dial in. That > > means at most a handful of routes per dial-up concentrator in the > > interior routing protocol. If everyone has their own /48, that means > > a route in the IGP for each customer that's online. There are no > > hard and fast rules about how many routes you can have in an > > IGP, but somewhere between 10k and 1M you run into trouble. > > this is an interesting point, but I think it has more to do with whether > the prefixes are statically bound to customers than the length of those > prefixes. why would giving customers static /64s result in fewer > routes in your IGP than giving them static /48s? in neither case is > there a direct correspondence between the customer's address and > the concentrator. IMHO, dialup is a bad example because static IPs per customer are rare; let's switch to the cable/dsl market. 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). S Stephen Sprunk "God does not play dice." --Albert Einstein CCIE #3723 "God is an inveterate gambler, and He throws the K5SSS dice at every possible opportunity." --Stephen Hawking