Getting a "portable" /19 or /20

> Perfectly aggregated networks are star-shaped.

No. They are tree shaped.

It seems pretty difficult to have all elements in a network
except one have only a default route if you have a tree shape,
assuming you don't mean a 3-node network...

> This is a result of the CIDR addressing architecture and is

I disagree, if insted we didn't aggregate into /19s or /20s but into /22s
and /23 there would be less unoptimum routing and larger (less scalable)
route tables.

Yeah, and if you deaggregate from /[overhead]s into /[overhead+2 or 3]
in any length CIDR routing system, you get 4 or 8 times the number
of prefixes, and make some people happy that they get more optimal
routing and make some people unhappy that they have to bear the
extra dynamism. In the interest of obviousness, "overhead" is the number
of bits necessary to identify a unicast address, and if you want to
use a larger value (like 19 or 20) just for fun, you get the same number
of potential prefixes whether your field is 32 bits or 128 bits or 2�� bits.

  Sean. (g'night)