bgp always-compare-med
Use this command to compare the Multi Exit Discriminator (MED) for paths from neighbors in different autonomous systems. Multi Exit Discriminator (MED) is used in best path selection by BGP. MED is compared after BGP attributes weight, local preference, AS-path and origin have been compared and are equal. MED comparison is done only among paths from the same autonomous system (AS). Use bgp always-compare-med command to allow comparison of MEDs from different ASs. The MED parameter is used to select the best path. A path with lower MED is preferred. If the bgp table shows the following and the always-compare-med is enabled:
Route1: as-path 400, med 300
Route2: as-path 200, med 200
Route3: as-path 400, med 250
Route1 is compared to Route2. Route2 is best of the two (lower MED). Next, Route2 is compared to Route3 and Route2 is chosen best path again (lower MED). If always-compare-med was disabled, MED is not taken into account when Route1 and Route2 are compared, because of different ASs and MED is compared for only Route1 and Route3. In this case, Route3 would be the best path. The selected route is also affected by the bgp deterministic-med command. Please see bgp deterministic-med command for details. If this command is used to compare MEDs for all paths, it should be configured on every BGP router in the AS.
Use the no parameter with this command to disallow the comparison.
Command Syntax
bgp always-compare-med
no bgp always-compare-med
Parameters
None
Default
By default, bgp always compare med is disabled
Command Mode
Router mode
Applicability
This command was introduced before OcNOS version 1.3.
Examples
#configure terminal
(config)#router bgp 100
(config-router)#bgp always-compare-med
Last modified date: 08/28/2023