What is the different type of route summarization available in OSPF?

There are two types of summarization:

Inter-area route summarization

External route summarization

i) Inter-Area Route Summarization

Inter-area route summarization is done on ABRs and it applies to routes from within the AS. It does not apply to external routes injected into OSPF via redistribution. In

order to take advantage of summarization, network numbers in areas should be assigned in a contiguous way to be able to lump these addresses into one range. To

specify an address range, perform the following task in router configuration mode:

area area-id range address mask

Where the "area-id" is the area containing networks to be summarized. The "address" and "mask" will specify the range of addresses to be summarized in one range.

The following is an example of summarization:

External route summarization

i) External route summarization is specific to external routes that are injected into OSPF via redistribution. Also, make sure that external ranges that are being

summarized are contiguous. Summarization overlapping ranges from two different routers could cause packets to be sent to the wrong destination. Summarization is

done via the following router ospf subcommand: