By configuring a RIPng router to advertise the summarized IPv6 address on an interface, you can save the space used by RIPng routes in the routing table. You can also set parameters to prevent an interface from learning the same summarized route.
This configuration is to configure the RIPng router to advertise the summarized IPv6 prefix rather than specific routes on an interface.
interface interface-type interface-number
ripng summary-address ipv6-address prefix-length [ avoid-feedback ]