IS-IS IPv4 route summarization allows users to create aggregate IPv4 addresses that include multiple groups of IPv4 addresses for a specific IS-IS level. IPv4 Routes redistributed from other routing protocols also can be summarized. It is similar to the OSPF area-range command. IS-IS IPv4 route summarization helps to reduce the size of the LSDB and the IPv4 routing table, and it also helps to reduce the chance of route flapping.
IPv4 route summarization supports:
Level 1, Level 1-2, and Level 2
route summarization for the IPv4 routes redistributed from other protocols
metric used to advertise the summary address is the smallest metric of all the more specific IPv4 routes