Reference Guide

518 | Equal Cost Multi-Path
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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:
Message 1 FTOS(conf)#hash-algorithm linecard 5 ip-sa-mask ff ip-da-mask ff
Message 2 % 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 traffic is flowing between linecard 1 and
linecard 2:
Message 3 hash-algorithm linecard 1 ip-sa-mask aa ip-da-mask 00
Message 4 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, then 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 or LAG is entered separately, both should fall
in the range of 0 to 23 or 24 to 47 since compression enable/disable is common for
both.
TeraScale and ExaScale support the range 0-47. The default for ExaScale is 24.
For EtherScale, only the range 0 to 15 is valid; 16 to 47 is considered as 15.
0-11
Compression Enabled
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