Reference Guide

382 | Interfaces
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Hash algorithm
The load-balance command discussed above selects the hash criteria applied to port channels.
If even distribution is not obtained with the load-balance command, the
hash-algorithm command can be
used to select the hash scheme for LAG and ECMP. The 12 bit Lag Hash can be rotated or shifted till the
desired hash is achieved.The default LAG hash algorithm is crc32LSB
Change the default algorithm and hash seed and apply it to ECMP and LAG.
Figure 20-14 shows a sample configuration for the
hash-algorithm command.
Figure 20-14. Command example: hash-algorithm
Hash Seed
Hash seed is used to compute the hash value. By default hash seed is chassis MAC 32 bits. we can also
change the hash seed by the following command.
Command Syntax Command Mode Purpose
hash-algorithm
[ecmp{crc16|crc16cc|crc32LSB|crc32M
SB|crc-upper|dest-ip|lsb|xor1|xor2|xor4|x
or8|xor16}|lag{crc16|crc16cc|crc32LSB|
crc32MSB|xor1|xor2|xor4|xor8|xor16}|
seed ]
CONFIGURATION Change the default algorithm and hash seed and apply
it to ECMP and LAG.
ecmp -- Options for ECMP hashing
lag -- Options for Lag hashing
seed -- Hash Algorithm seed for ECMP, LAG
Note: To achieve the functionality of hash-align
on the ExaScale platform, do not use CRC as an
hash-algorithm method. For ExaScale systems,
set the default hash-algorithm method to ensure
CRC is not used for LAG. For example,
hash-algorithm ecmp xor lag checksum nh-ecmp
checksum
For details on the algorithm choices, refer to the
command details in the IP Routing chapter of the
FTOS Command Reference.
Command Syntax Command Mode Purpose
hash-algorithm seed {seed value} CONFIGURATION Change the Hash algorithm seed value to get better
hash value
FTOS(conf)##hash-algorithm ecmp xor1
FTOS(conf)#