CEF Load Balancing Algorithm
- By default, CEF uses per-destination load balancing
- In the event of an existing parallel path, a hash algorithm is used to determine the path to be chosen for each destination
- In cases when load sharing is done simultaneously on interfaces of different physical types, such as serial and tunnel, CEF takes the single path.
- In order to utilize all the parallel paths in CEF and load balance the traffic, you must enable per-packet load balancing when you have different physical interfaces like serial and tunnel.
- So, on the basis of the configuration and topology (serial or tunnel), load sharing can fail to work correctly with the default CEF load balancing mode.
Links:
https://www.cisco.com/c/en/us/support/docs/ip/border-gateway-protocol-bgp/5212-46.html#anc12