Administrator Guide

Version Description
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.
hash-algorithm ecmp
Change the hash algorithm used to distribute traffic flows across an ECMP (equal-cost multipath routing) group.
Z9000
Term heading
Description heading
Syntax
hash-algorithm ecmp {crc-upper} | {dest-ip} | {lsb}
To return to the default hash algorithm, use the no hash-algorithm ecmp command.
Parameters
crc-upper Uses the upper 32 bits of the key for the hash computation. The default is crc-
lower.
dest-ip Uses the destination IP for ECMP hashing. The default is enabled.
lsb Returns the LSB of the key as the hash. The default is crc-lower.
Defaults
● crc-lower
● dest-ip enabled
Command Modes CONFIGURATION
Command
History
This guide is platform-specific. For command information about other platforms, refer to the relevant Dell
Networking OS Command Line Reference Guide.
Equal Cost Multi-Path (ECMP) 437