Reference Guide

hash-algorithm ecmp
Change the hash algorithm used to distribute traffic flows across an ECMP (equal-cost multipath routing)
group.
S5000
Syntax
hash-algorithm ecmp {crc-upper} | {crc} | {dest-ip} | {lsb} |
{xor}
To return to the default hash algorithm, use the no hash-algorithm ecmp
command.
Parameters
crc Uses specified polynomicals or bits of computed cyclic
redundancy checks (CRC) for the hash computation.
crc-upper Uses the upper 32 bits of the key for the hash computation.
dest-ip Uses the destination IP for ECMP hashing.
lsb Returns the LSB of the key as the hash.
xor Uses the lower 8 bits of the key for the hash computation.
Defaults
• crc-lower
• dest-ip enabled
Command
Modes
CONFIGURATION
Command
History
Version 9.0(1.3) Introduced on the S5000.
Usage
Information
The hash value calculated with the hash-algorithm command is unique to the
entire chassis. The default ECMP hash configuration is crc-lower. This takes the
lower 32 bits of the hash key to compute the egress port and is the “fall-back”
configuration if you have not configured anything else.
The different hash algorithms are based on the number of ECMP group members
and packet values. The default hash algorithm yields the most balanced results in
various test scenarios, but if the default algorithm does not provide satisfactory
distribution of traffic, use this command to designate another algorithm.
When a member leaves or is added to the ECMP group, the hash algorithm is
recalculated to balance traffic across the members.
Related
Commands
load balance
Equal Cost Multi-Path Overview (ECMP)
455