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Cisco ME 3400 EthernetAccess Switch SoftwareConfiguration Guide
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Chapter32 Configuring IP Unicast Routing Configuring BGP
To delete an aggregate entry, use the no aggregate-address address mask router configuration
command. To return options to the default values, use the command with keywords.
Configuring Routing Domain Confederations
One way to reduce the IBGP mesh is to divide an autonomous system into multiple subautonomous
systems and to group them into a single confederation that appears as a single autonomous system . Each
autonomous system is fully meshed within itself and has a few connections to other autonomous systems
in the same confederation. Even though the peers in different autonomous systems have EBGP sessions,
they exchange routing information as if they were IBGP peers. Specifically, the next hop, MED, and
local preference information is preserved. You can then use a single IGP for all of the autonomous
systems.
To configure a BGP confederation, you must specify a confederation identifier that acts as the
autonomous system number for the group of autonomous systems.
Beginning in privileged EXEC mode, use these commands to configure a BGP conf ed erat ion :
Step4 aggregate-address address mask as-set (Optional) Generate AS set path information. This command
creates an aggregate entry following the same rules as the previous
command, but the advertised path will be an AS_SET consisting of
all elements contained in all paths. Do not use this keyword when
aggregating many paths because this route must be continually
withdrawn and updated.
Step5 aggregate-address address-mask
summary-only (Optional) Advertise summary addresses only.
Step6 aggregate-address address mask
suppress-map map-name (Optional) Suppress selected, more specific routes.
Step7 aggregate-address address mask
advertise-map map-name (Optional) Generate an a ggregate ba sed on c on ditio ns spec ified by
the route map.
Step8 aggregate-address address mask
attribute-map map-name (Optional) Generate an aggregate with attributes specified in the
route map.
Step9 end Return to privileged EXEC mode.
Step10 show ip bgp neighbors [advertised-routes] Verify the configuration.
Step11 copy running-config startup-config (Optional) Save your entries in the configuration file.
Command Purpose
Command Purpose
Step1 configure terminal Enter global configuration mode.
Step2 router bgp autonomous-system Enter BGP router configuration mode.
Step3 bgp confederation identifier autonomous-system Configure a BGP confederation identifier.
Step4 bgp confederation peers autonomous-system
[autonomous-system ...] Specify the autonomous systems that belong to the
confederation and that will be treated as special EBGP peers.
Step5 end Return to privileged EXEC mode.