Administrator Guide

Version Description
9.7(0.0) Introduced on the S6000-ON.
8.3.19.0 Introduced on the S4820T.
8.3.11.1 Introduced on the Z9000.
8.3.7.0 Introduced on the S4810.
8.3.1.0 Introduced on the E-Series.
Usage
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.
Z9000
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.
9.0.2.0 Introduced on the S6000.
9.0.0.0 Introduced on the Z9000.
8.3.10.0 Introduced on the S4810.
Usage
Information
You must save the new ECMP settings to the startup-config (write-mem) then reload the system for
the new settings to take effect.
Related
Commands
show ip cam stack-unit – Display content-addressable memory (CAM) entries for an S-Series switch.
440 Equal Cost Multi-Path (ECMP)