Administrator Guide

Version 7.7.1.1 Added the nh-ecmp option.
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.
The hash value calculated with the hash-algorithm command is unique to the
entire chassis. The hash algorithm command with the stack—unit option changes
the hash for a particular stack—unit by applying the mask specified in the IPSA and
IPDA fields.
The stack-unit option is applicable with the lag-hash-align microcode only. Any
other microcode returns an error message as follows:
• Dell(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, Dell Networking OS maintains bi-
directionality with masks set to XX 00 for stack-unit 1 and 00 XX for stack-unit 2
(ip-sa-mask and ip-da-mask). The mask value must be the same for both
stack-units when using multiple stack-units as ingress (where XX is any value
from 00 to FF for both stack-units). 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.
Equal Cost Multi-Path (ECMP)
549