ECS4660-28F_Management Guide-R03

C HAPTER 51 | IP Routing Commands
Border Gateway Protocol (BGPv4)
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DEFAULT SETTING
100
COMMAND USAGE
Local preference is a discretionary attribute applied to a route during the
BGP best path selection process. It is exchanged only between iBGP peers,
and used to determine local policy.
EXAMPLE
Console(config-router)#bgp default local-preference 100
Console(config-router)#
bgp
deterministic-med
This command enforces deterministic comparison of the MED attribute
between all paths received from the same AS, ensuring that selection of
the best path will always be the same, regardless of the order in which the
paths are received by the local router. Use the no form to disable this
feature.
SYNTAX
[no] bgp deterministic-med
COMMAND MODE
Router Configuration
DEFAULT SETTING
Disabled
COMMAND USAGE
◆ The MED is compared after BGP attributes weight, local preference, AS-
path and origin have been compared and are equal. When deterministic
comparison of the MED is enabled, all paths for the same route prefix
(received from peers within the same AS) are grouped together and
arranged according to their MED value. Based on this comparison, the
best path is then chosen.
◆ The router immediately groups and sorts all local paths when this
command is entered. For correct results, deterministic comparison of
the MED must be configured in the same manner (enabled or disabled)
on all routers in the local AS.
◆ If deterministic comparison of the MED is not enabled, route selection
can be affected by the order in which routes are received.
◆ This command compares the MED when choosing routes advertised by
different peers in the same AS. To compare the MED when choosing
routes from neighbors in different ASs, use the bgp always-compare-
med command.