Dell S4048T, Configuration Manual

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4 Configuring different hash algorithms at different tiers. For example, Router A could use crc16 as the
hash algorithm while router B can use XOR16 as the hash algorithm.
Configuration and Benefits
The preceding anti-polarization techniques require some coordinated configuration of network nodes to
solve the problem and these techniques are not scalable when the number of tiers in the network is high.
Flow based hashing specifically addresses this using
Macro flow-based Hash function. It facilitates a dynamic
hash function selection across different nodes in a network on a macro flow basis, thus reducing unfair
distribution of bandwidth between members and starvation.
Selection of Algorithms is available under flow-based-hashing enabling another level of randomness in hash
selection. CLI to enable flow-based hashing is shown in the given example:
Dell_GW1(conf)#hash-algorithm ecmp flow-based-hashing ?
crc16 CRC16_BISYNC - 16 bit CRC16-bisync polynomial(default)
crc16cc CRC16_CCITT - 16 bit CRC16 using CRC16-CCITT polynomial
crc32MSB CRC32_UPPER - MSB 16 bits of computed CRC32
crc32LSB CRC32_LOWER - LSB 16 bits of computed CRC32
xor1 CRC16_BISYNC_AND_XOR1 - Upper 8 bits of CRC16-BISYNC and
lower 8 bits of xor1
xor2 CRC16_BISYNC_AND_XOR2 - Upper 8 bits of CRC16-BISYNC and
lower 8 bits of xor2
xor4 CRC16_BISYNC_AND_XOR4 - Upper 8 bits of CRC16-BISYNC and
lower 8 bits of xor4
xor8 CRC16_BISYNC_AND_XOR8 - Upper 8 bits of CRC16-BISYNC and
lower 8 bits of xor8
xor16 CR16 - 16 bit XOR]
Example to view show hash-algorithm:
Dell(conf)#hash-algorithm ecmp flow-based-hashing crc16
Dell(conf)#end
Dell#show hash-algorithm
Hash-Algorithm
linecard 0 Port-Set 0
Seed 185270328
Hg-Seed 185282673
Equal Cost Multi-Path (ECMP) 375