Service Manual

Command History
Version Description
9.9(0.0) Introduced on the FN IOM.
9.2(0.0) Introduced on the MXL 10/40GbE Switch IO Module.
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.
The Dell Networking OS 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.
Syntax
ip ecmp-group {maximum-paths | {number} {path-fallback}
To negate a command, use the no ip ecmp-group maximum-paths 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
9.9(0.0) Introduced on the FN IOM.
9.2(0.0) Introduced on the MXL 10/40GbE Switch IO Module.
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.
450 Equal Cost Multi-Path (ECMP)