Tuning the BGP Best-Path Calculation
Perform this task to change the default BGP best-path calculation behavior.
SUMMARY STEPS
1.
configure
2.
router bgp as-number
3.
bgp bestpath med missing-as-worst
4.
bgp bestpath med always
5.
bgp bestpath med confed
6.
bgp bestpath as-path ignore
7.
bgp bestpath compare-routerid
8.
commit
DETAILED STEPS
PurposeCommand or Action
configure
Step 1
Specifies the autonomous system number and enters the BGP
configuration mode, allowing you to configure the BGP
routing process.
router bgp as-number
Example:
RP/0/RSP0/CPU0:router(config)# router bgp 126
Step 2
Directs the BGP software to consider a missing MED attribute
in a path as having a value of infinity, making this path the
least desirable path.
bgp bestpath med missing-as-worst
Example:
RP/0/RSP0/CPU0:router(config-bgp)# bgp
bestpath med missing-as-worst
Step 3
Configures the BGP speaker in the specified autonomous
system to compare MEDs among all the paths for the prefix,
bgp bestpath med always
Example:
RP/0/RSP0/CPU0:router(config-bgp)# bgp
bestpath med always
Step 4
regardless of the autonomous system from which the paths
are received.
Enables BGP software to compare MED values for paths
learned from confederation peers.
bgp bestpath med confed
Example:
RP/0/RSP0/CPU0:router(config-bgp)# bgp
bestpath med confed
Step 5
Cisco ASR 9000 Series Aggregation Services Router Routing Configuration Guide, Release 5.3.x
88
Implementing BGP
Tuning the BGP Best-Path Calculation
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