ECS4660-28F_Management Guide-R03

C HAPTER 51 | IP Routing Commands
Border Gateway Protocol (BGPv4)
– 1853 –
Route Metrics and Selection
bgp always-
compare-med
This command allows comparison of the Multi Exit Discriminator (MED) for
paths advertised from neighbors in different autonomous systems. Use the
no form to disable this feature.
SYNTAX
[no] bgp always-compare-med
COMMAND MODE
Router Configuration
DEFAULT SETTING
Disabled
COMMAND USAGE
◆ The MED is an optional non-transitive
30
attribute used to discriminate
among multiple exit points to a neighboring autonomous system. A
path with a lower MED is preferred over a path with a higher MED.
◆ By default, during best-path selection, the MED is compared only
among paths from the same autonomous system. This command allows
the comparison of MEDs among different paths regardless of the
autonomous system from which the paths are received.
◆ The bgp deterministic-med command can be used to enforce
comparison of the MED value between all paths received from within
the same autonomous system.
EXAMPLE
This example assumes that a peer router is advertising the same route
prefix through the two ASes (100 and 300) to the same AS (200), each of
which carries a different MED.
Console(config-router)#bgp always-compare-med
Console(config-router)#
bgp bestpath
as-path ignore
This command ignores the AS path length in the selection of a path. Use
the no form to disable this feature.
SYNTAX
[no] bgp bestpath as-path ignore
COMMAND MODE
Router Configuration
30. If a router does not understand an optional non-transitive attribute, it will be removed.