Reference Guide

To change the IP traffic load-balancing default, use the following command.
• Replace the default IP 4-tuple method of balancing traffic over a port channel.
CONFIGURATION mode
[no] load-balance {ip-selection [dest-ip | source-ip]} | {mac [dest-mac |
source-dest-mac | source-mac]} | {tcp-udp enable} | {ing-port}
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 the 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 the TCP/UDP source and destination ports.
– ing-port — Distribute traffic based on the port ID of the IP source address.
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 {algorithm-number} | {ecmp {checksum|crc|xor} [number]} lag
{checksum|crc|xor][number]}nh-ecm p {[checksum|crc|xor] [number]}}| {linecard
number ip-sa-mask value ip-da-mask value}
For more information about algorithm choices, refer to the command details in the IP Routing chapter of the FTOS
Command Reference Guide .
• Change to another algorithm.
CONFIGURATION mode
hash-algorithm ecmp {crc-upper} | {dest-ip} | {lsb}
Example of the hash-algorithm Command
FTOS(conf)#hash-algorithm ecmp xor 26 lag crc 26 nh-ecmp checksum 26
FTOS(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:
• 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.
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