Reference Guide

The following is a list of the FTOS version history for this command.
Version 8.3.19.0 Introduced on the S4820T.
Version 8.3.11.1 Introduced on the Z9000.
Version 8.3.10.0 Introduced on the S4810.
Version 8.1.1.0 Introduced on the E-Series ExaScale.
Version 7.8.1.0 Added the nh-ecmp option.
Version 7.7.1.1 Added the nh-ecmp option.
Version 6.5.1.0 Added the line card option on TeraScale only.
Version 6.3.1.0 Added support for ECMP and LAG on TeraScale only.
Usage
Information
To ensure that CRC is not used for LAG, set the default hash-algorithm method on ExaScale
systems. For example,hash-algorithm ecmp xor lag checksum nh-ecmp
checksum.
To achieve the functionality of hash-align on the ExaScale platform, do not use CRC as a hash-
algorithm method.
The hash value calculated with the hash-algorithm command is unique to the entire chassis.
The hash algorithm command with the line card option changes the hash for a particular line
card by applying the mask specified in the IPSA and IPDA fields.
The line card option is applicable with the lag-hash-align microcode only (refer to cam-profile
(Config)). Any other microcode returns an error message as follows:
• FTOS(conf)#hash-algorithm linecard 5 ip-sa-mask ff ip-da-
mask ff
• % Error: This command is not supported in the current
microcode configuration
In addition, the linecard number ip-sa-mask value ip-da-mask value
option has the following behavior to maintain bi-directionality:
• When hashing is done on both IPSA and IPDA, the ip-sa-mask and ip-da-mask
values must be equal. (Single Linecard).
• When hashing is done only on IPSA or IPDA, FTOS maintains bi-directionality with
masks set to XX 00 for line card 1 and 00 XX for line card 2 (ip-sa-mask and ip-
da-mask
). The mask value must be the same for both line cards when using multiple
line cards as ingress (where XX is any value from 00 to FF for both line cards). For
example, assume that traffic is flowing between linecard 1 and linecard 2:
• hash-algorithm linecard 1 ip-sa-mask aa ip-da-mask 00
• hash-algorithm linecard 2 ip-sa-mask 00 ip-da-mask aa
The different hash algorithms are based on the number of Port Channel members and packet
values. The default hash algorithm (number 0) yields the most balanced results in various test
scenarios, but if the default algorithm does not provide a satisfactory distribution of traffic, use
the hash-algorithm command to designate another algorithm.
When a Port Channel member leaves or is added to the Port Channel, the hash algorithm is
recalculated to balance traffic across the members.
On TeraScale, if the keyword ECMP or LAG is not entered, FTOS assumes it to be common for
both. If the keyword ECMP orLAG is entered separately, both fall in the range of from 0 to 23 or
from 24 to 47 because compression enable/disable is common for both keywords.
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