CIDR allocation question

Vadim Antonov avg at
Fri Apr 8 22:25:38 UTC 1994

>        Given a site that has a need for a certain number of
>addresses, but probably will never need additional networks to fill
>out a power of two allocation. Should we allocate the larger block to
>the site anyway to reduce the size of the routing table, or should we
>allocate two CIDR blocks?

>        For example, if a site will only realisticly need 6 class C's,
>should we allocate a block of 8, or a block of four and a block of two.

Given that the immediate threat is the growth of routing tables, not
IP address space exhaustion it's better to allocate powers of 2-sized
blocks and announce only one route.  The IP space overhead is about 30% but
routing table savings are at least 50%.

Actually, CIDR allocation helps to slow down IP address allocation
by providing most of organizations an alternative to class B.  We have
sliced an eqivalent of 4 calss B to about 100 customers!  So the
2008 doomsday estimate may be kind of pessimistic :-)


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