Reference Guide

Interfaces | 433
To change the IP traffic load balancing default on the C-Series and S-Series, 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.
For the E-Series TeraScale and ExaScale, you can select one of 47 possible hash algorithms .
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
}
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.
Command Syntax Command Mode Purpose
hash-algorithm {algorithm-number} |
{ecmp {checksum|crc|xor}
[number]} lag
{checksum|crc|xor][number]}nh-ec
mp
{[checksum|crc|xor] [number]}}|
{linecard number ip-sa-mask value
ip-da-mask value}
CONFIGURATION Change the default (0) to another algorithm and apply
it to ECMP, LAG hashing, or a particular line card.
Note: To achieve the functionality of hash-align on the
ExaScale platform, do not use CRC as an
hash-algorithm method. For ExaScale systems, set the
default hash-algorithm method to ensure CRC is not
used for LAG. For example,
hash-algorithm ecmp
xor lag checksum nh-ecmp checksum
For details on the algorithm choices, refer to the
command details in the IP Routing chapter of the
FTOS Command Line Reference.
Note: E-Series systems require the lag-hash-align microcode be configured in the in the CAM profile.
E-Series TeraScale e
t
includes this microcode as an option with the Default cam profile. E-Series
ExaScale e
x
systems require that a CAM profile be created and specifically include lag-hash-align
microcode.