BGP Equal cost multipath

By default, BGP does not perform load balancing. BGP - Attributes and path selection|BGP will select only a single path for a prefix. You can see this from the very last attribute that is examined. If all other attributes are the same, at the very end, a BGP router will prefer the path with the lowest neighbor IP address. This is the last tiebreaker.

To enable load sharing, you must enable BGP multipath load sharing using the BGP command:

maximum-paths

This will allow a BGP router to select additional paths to a destination as long as the following attributes for those paths are the same:

• Weight
• Local Preference
• AS Path (both AS number and AS path length)
• Origin code
• MED
• IGP metric (this depends upon the implementation)

Take a look at BGP - Multipath Attribute Prerequisites for more information about these prerequisites.

Take a look at the BGP Equal cost multipath configuration syntax for more information about the command.

Links

https://networklessons.com/bgp/bgp-multipath-load-sharing-ibgp-and-ebgp https://networklessons.com/bgp/bgp-additional-paths