Hash-based algorithms prioritize session stickiness
—The
IP Modulo
and
IP
Hash
algorithms use hashes based on information in the packet
header, such as source and destination address. Because the header
of each flow in a given session contains the same source and destination
information, these options prioritize session
stickiness.
If you choose the
IP Hash
algorithm, the
hash can be based on the source and destination addresses, or the
hash can be based on the source address only. Using an IP hash based
on only the source address causes all sessions belonging to the
same source IP address to always take the same path from available
multiple paths. Thus the path is considered sticky and is easier
to troubleshoot if necessary. You can optionally set a
Hash
Seed
value to further randomize load balancing if you
have a large number of sessions to the same destination and they’re
not being distributed evenly over the ECMP links.