3Com 3C13618 Command Reference Manual page 521

Routing Protocol
The routes from different subnets of the same natural network segment will be
summarized When sending to other network segments, it will not only largely
decrease the occupation of network resources, but also the size of the routing table.
For related commands, see rip version.
Example
# Set the RIP Version 2 on Serial 0 and disable the route summary function.
[3Com-Serial0] rip version 2
[3Com-Serial0] quit
[3Com] rip
[3Com-rip] undo summary
33