Reference Guide

420 | Interfaces
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To change the IP traffic load balancing default on the S5000, use the following command:
Hash algorithm
The load-balance command discussed above selects the hash criteria applied to port channels.
If even distribution is not obtained with the load-balance command, the
hash-algorithm command can be
used to select the hash scheme for LAG, ECMP and NH-ECMP. The 12 bit Lag Hash can be rotated or
shifted till 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.
The following example shows a sample configuration for the
hash-algorithm command.
Dell(conf)#hash-algorithm ecmp xor 26 lag crc 26 nh-ecmp checksum 26
Dell(conf)#
On the S5000, the hash-algorithm command is specific to ECMP groups. The default ECMP hash
configuration is
crc-lower. This takes the lower 32 bits of the hash key to compute the egress port. Other
options for ECMP hash-algorithms are:
•
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 — always uses the least significant bit of the hash key to compute the egress port
To change to another method, use the following command in the CONFIGURATION mode:
Command Syntax Command Mode Purpose
[
no] load-balance {ip-selection
[dest-ip | source-ip]} | {mac
[dest-mac | source-dest-mac |
source-mac]} | {tcp-udp enable} |
{ing-port}
CONFIGURATION Replace the default IP 4-tuple method of balancing
traffic over a port channel. You can select one, two, or
all three of the following basic hash methods
ip-selection [dest-ip | source-ip]—Distribute IP traffic
based on IP destination or source address.
mac [dest-mac | source-dest-mac | source-mac]—
Distribute IPV4 traffic based on the destination or source
MAC address, or both, along with the VLAN, Ethertype,
source module ID and source port ID.
tcp-udp enable—Distribute traffic based on TCP/UDP
source and destination ports.
ing-port —Distribute traffic based on the port ID of the IP
source address.
Command Syntax Command Mode Purpose
hash-algorithm ecmp {crc-upper} |
{dest-ip} | {lsb}
CONFIGURATION Change to another algorithm.