Dell S4820T, Configuration Manual

Page: 450 / 1178

• 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|crc32LSB|crc32MSB|crc-upper|dest-ip |lsb
|xor1| xor2| xor4| xor8| xor16}|lag{crc16|crc16cc|crc32LSB|crc32MSB|xor1|
xor2|xor4|xor8|xor16}| seed ]
For more information about algorithm choices, refer to the command details in the IP Routing
chapter of the Dell Networking OS Command Reference Guide .
• Change the Hash algorithm seed value to get better hash value
Hash seed is used to compute the hash value. By default hash seed is chassis MAC 32 bits. we can also
change the hash seed by the following command.
CONFIGURATION mode
hash-algorithm seed {seed value}
• Change to another algorithm.
CONFIGURATION mode
hash-algorithm [ecmp{crc16|crc16cc|crc32LSB|crc32MSB|crc-upper|dest-ip|lsb|
xor1|xor2|xor4|xor8|xor16}]
Example of the
hash-algorithm
Command
Dell(conf)#hash-algorithm ecmp xor 26 lag crc 26 nh-ecmp checksum 26
Dell(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.
•
lsb
—uses always return the LSB of the key as the hash
•
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.
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Interfaces