Summarization

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• 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 <asn> 192.168.0.1 255.255.255.0 <admin-distance>

OSPF

ASBR - config-router# summary-address [<ip> <mask> | <prefix> <mask>] [not-advertise] [tag <value>] (summarizes routes as injected into OSPF)

ABR - config-router# area 1 range <ip> <mask> [advertise|not-advertise] [cost <value>]