Lecture 7: Planning the IP Addressing Hierarchy

Planning for Information Network
Lecture 7: Planning the IP Addressing Hierarchy

Hierarchical Addressing
** Each IP address is divided into a prefix and a suffix.
- Prefix identifies network to which computer is attached
- Suffix identifies computer within that network
** Address format makes routing efficient

The IP addressing scheme is hierarchical, and IP routers make hierarchical decisions.
Recall that an IP address comprises a prefix part and a host part (suffix).
A router has to know only how to reach the next hop; it does not have to know the details of how to reach an end node that is not local.
Routers use the prefix to determine the path for a destination address that is not local. The host part is used to reach local hosts.

Route Summarization
With route summarization, also referred to as route aggregation or supernetting, one route in the routing table represents many other routes.
Summarizing routes reduces the routing update traffic and reduces the number of routes in the routing table and overall router overhead in the router receiving the routes.
In a hierarchical network design, effective use of route summarization can limit the impact of topology changes to the routers in one section of the network.