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Information
Deterministic ECMP sorts ECMPs in order even though RTM provides them in a
random order. However, the hash algorithm uses as a seed the lower 12 bits of the
chassis MAC, which yields a different hash result for every chassis. This behavior
means that for a given flow, even though the prefixes are sorted, two unrelated
chassis select different hops.
FTOS provides a CLI-based solution for modifying the hash seed to ensure that on
each configured system, the ECMP selection is same. When configured, the same
seed is set for ECMP, LAG, and NH, and is used for incoming traffic only.
NOTE: While the seed is stored separately on each port-pipe, the same seed is
used across all CAMs.
You cannot separate LAG and ECMP but you can use different algorithms
across the chassis with the same seed. If LAG member ports span multiple
port-pipes and line cards, set the seed to the same value on each port-pipe to
achieve deterministic behavior.
If the hash algorithm configuration is removed, the hash seed does not go to
the original factory default setting.
ip ecmp-group
Enable and specify the maximum number of ecmp that the L3 CAM hold for a route, By default, when
maximum paths are not configured, the CAM can hold a maximum of 16 ecmp per route.
S4820T
Syntax
ip ecmp-group {maximum-paths | {number} {path-fallback}
To negate a command, use the no ip ecmp-group maximum-paths {number}
command.
Parameters
maximum-
paths
Specify the maximum number of ECMP for a route. The
range is 2 to 64.
path-fallback Use the keywords path-fallback to enable this feature. If
you enable the feature, re-enter this keyword to disable the
feature.
Defaults 16
Command
Modes
CONFIGURATION
Command
History
Version Description
9.7(0.0) Introduced on the S6000-ON.
690
Equal Cost Multi-Path (ECMP)