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Configurable ECMP Hash Algorithm (C- and S-Series)
Configurable ECMP Hash Algorithm (C- and S-Series) is available on platforms: c s
On C-Series and S-Series, the hash-algorithm command is specific to ECMP groups and has a different
default from the E-Series (see Configurable Hash Algorithm (E-Series)). The default ECMP hash
configuration is
crc-lower, which takes the lower 32 bits of the hash key to compute the egress port. The
hash value calculated with the hash algorithm is unique to the entire chassis.
Other options for the ECMP hash-algorithm 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 a different hash scheme for ECMP, use the following command in the CONFIGURATION
mode:
The different hash algorithms for ECMP are based on the number of ECMP group members and packet
values. The default hash algorithm yields the most balanced results in various test scenarios, but if the
default algorithm does not provide satisfactory distribution of traffic, then use this command to designate
another algorithm.
When a member leaves or is added to the ECMP group, the hash algorithm is recalculated to balance traffic
across the members.
Command Syntax Command Mode Purpose
hash-algorithm ecmp {crc-lower |
crc-upper | dest-ip | lsb}
Default: crc-lower
CONFIGURATION Change to another algorithm.