2.5 Route Summarization Overview
2.5.3 Summarizing addresses in a VLSM-designed network
A VLSM design allows for maximum use of IP addresses, as well as more efficient routing update communication when using hierarchical IP addressing. In the main figure, for example, route summarization occurs at the following two levels:
  • Router C summarizes two routing updates from networks 172.16.32.64/26 and 172.16.32.128/26 into a single update, 172.16.32.0/24.
  • Router A receives three different routing updates, but summarizes them into a single routing update before propagating it to the Internet.