Classless Inter-Domain Routing (CIDR)-RFC1338 Allows arbitrary split between network& host part of address Do not use classes to determine network d Use common part of address as network number E.g., addresses 192.4.16-192.4.31 have the first 20 bits in common. Thus. we use these 20 bits as the network number>192.4.16/20 Enables more efficient usage of address space (and router tables)> How? Use single entry for range in forwarding tables Combined forwarding entries when possible 9-26-06 Lecture 9: IP Packets 79-26-06 Lecture 9: IP Packets 7 Classless Inter-Domain Routing (CIDR) – RFC1338 • Allows arbitrary split between network & host part of address • Do not use classes to determine network ID • Use common part of address as network number • E.g., addresses 192.4.16 - 192.4.31 have the first 20 bits in common. Thus, we use these 20 bits as the network number → 192.4.16/20 • Enables more efficient usage of address space (and router tables) → How? • Use single entry for range in forwarding tables • Combined forwarding entries when possible