Load balancing Hash

Load balancing Hash

2 equal cost path to a Destination, decision is made by a hashing algorithm , which uses XOR on  lower bits of SIP/DIP to select one link
which turns out the same across all Nodes in the path.

Use of the same hash algorithm and same hash input which results in the use of a single Equal-Cost Multi-Path (ECMP) link for ALL flows


Default IOS load balancing across equal paths 4, BGP 1, others maximum 6

  2 supported   

•  Per-destination  all packets same path , same packet order   

 Route cache for every destination address, host within the same subnet could use  different paths

• Per packet :  load balancing guaranteed , packets arrive at different order, the packets are distributed round robin over the available paths

Each SIP/DIP session is assigned to an active path
The session-to-path assignment is done using a hash function that takes the source and destination IP addresses and a unique hash ID that randomizes the assignment across the end-to-end path.