Administrator Guide

Dell EMC Networking OS allows you to modify the hashing algorithms used for flows and for fragments. The load-balance and hash-
algorithm commands are available for modifying the distribution algorithms.
Changing the Hash Algorithm
The load-balance command selects the hash criteria applied to port channels.
If you do not obtain even distribution with the load-balance command, you can use the hash-algorithm command to select the
hash scheme for LAG, ECMP and NH-ECMP. You can rotate or shift the 12–bit Lag Hash until the desired hash is achieved.
The nh-ecmp option allows you to change the hash value for recursive ECMP routes independently of non-recursive ECMP routes. This
option provides for better traffic distribution over available equal cost links that involve a recursive next hop lookup.
To change to another algorithm, use the second command.
• Change the default (0) to another algorithm and apply it to ECMP, LAG hashing, or a particular line card.
CONFIGURATION mode
hash-algorithm {ecmp {crc16 | crc16cc | crc32MSB | crc32LSB | crc-upper | dest-ip | flow-
based-hashing {crc16|crc16cc|crc32MSB|crc32LSB|xor1|xor2|xor4|xor8|xor16}|lsb | xor1 | xor2 |
xor4 | xor8 | xor16}[[hg {crc16 | crc16cc | crc32MSB | crc32LSB | xor1 | xor2 | xor4 | xor8 |
xor16}]| [lag {crc16 | crc16cc | crc32MSB | crc32LSB | xor1 | xor2 | xor4 | xor8 | xor16 }]
[stack-unit|linecard number | port-set number | [hg—seed seed-value | seedseed-value
For more information about algorithm choices, refer to the command details in the IP Routing chapter of the Dell EMC Networking OS
Command Reference Guide.
• Change to another algorithm.
CONFIGURATION mode
DellEMC(conf)#hash-algorithm ecmp xor 26 lag crc 26 nh-ecmp checksum 26
DellEMC(conf)#
The hash-algorithm command is specific to ECMP group. The default ECMP hash configuration is crc-lower. This command takes
the lower 32 bits of the hash key to compute the egress port. Other options for ECMP hash-algorithms are:
• crc16 — uses 16 bit CRC16-bisync polynomial
• crc16cc — uses 16 bit CRC16 using CRC16-CCITT polynomial
• crc32LSB — uses LSB 16 bits of computed CRC32
• crc32MSB — uses MSB 16 bits of computed CRC32(default)
• crc-upper — uses the upper 32 bits of the hash key to compute the egress port.
• dest-ip — uses destination IP address as part of the hash key.
• flow-based-hashing — uses flow-based-hashing followed by the algorithm crc16 |crc16cc |crc32MSB |crc32LSB |xor1 |xor2 |
xor4 |xor8 | xor16.
• lsb — uses the least significant bit of the hash key to compute the egress port.
• xor1 — uses Upper 8 bits of CRC16-BISYNC and lower 8 bits of xor1
• xor2 — Upper 8 bits of CRC16-BISYNC and lower 8 bits of xor2
• xor4 —Upper 8 bits of CRC16-BISYNC and lower 8 bits of xor4
• xor8 — Upper 8 bits of CRC16-BISYNC and lower 8 bits of xor8
• xor16 — uses 16 bit XOR.
Bulk Configuration
Bulk configuration allows you to determine if interfaces are present for physical interfaces or configured for logical interfaces.
Interface Range
An interface range is a set of interfaces to which other commands may be applied and may be created if there is at least one valid
interface within the range.
Bulk configuration excludes from configuration any non-existing interfaces from an interface range. A default VLAN may be configured
only if the interface range being configured consists of only VLAN ports.
Interfaces
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