Route summarization involves creating a single route which represents more than one subnet, and is a contiguous range of subnets implied by the route. Routes whose subnet falls within the range are referred to as component routes.
Certain routing protocols handle route summarization in different ways, here are a few points in which they are common:
- Advertised summary is assigned the metric of the lowest component subnet
- Router does not advertise component subnets
- Router does not advertise the summary when its routing table does not have any component subnets
- the summarizing router creates a local route summary with destination of null0 to prevent loops
- summary routes reduce the size of the routing table and improves convergence
- summary routes decrease the amount of specific information in routing tables causing suboptimal routing