IP addressing: CIDR
classful addressing:
- inefficient use of address space, address space exhaustion
- e.g., class B net allocated enough addresses for 65K hosts, even if only 2K hosts in that network
CIDR: Classless InterDomain Routing
- network portion of address of arbitrary length
- address format: a.b.c.d/x, where x is # bits in network portion of address