Route Summarization helps to make the routing table smaller and still allow for complete connectivity. Its also helps in bringing down the router CPU when installing multiple routes in the routing table.
IPv6 EIGRP route summarization is similar to IPv4. The summarization is performed on interface-basis by command <ipv6 summary-address eigrp as-number ipv6-address> . After configuring the summarization command the router drops IPv6 EIGRP relationships to reestablish them again, this renew input events and make neighbors rebuild their topology tables and perform DUAL algorithm local computation again using the new advertisements from the router who reconfigured summarization.
In this document, two routers R1 and R2 are forming IPv6 EIGRP relationship through interface Fa 0/0 under AS 10. Further R2, is configured to advertise ipv6 prefixes of Loopbak 1, 2, 3, 4 and 10. IPv6 addresses of Lo Int 1/2/3/4 are somewhat similar with only change in the 8th block. (Please see the topology diagram). A summary of these IPv6 prefixes is sent to R1.