Summarization


 * advertised summary has same metric as lowest metric component subnet
 * does not advertise component subnets
 * does not advertise when routing table doesnt have component subnet
 * creates local route to summary; destination null0 interface; preventing routing loops

=Protocols=

__EIGRP__

 * doesnt advertise the admin-distance; uses it to decide if should be put in the grouting table; default is 5

config-if# ip summary-address eigrp 192.168.0.1 255.255.255.0 

__OSPF__

 * ASBR** - config-router# summary-address [ | ] [not-advertise] [tag ] (summarizes routes as injected into OSPF)


 * ABR** - config-router# area 1 range  [advertise|not-advertise] [cost ]