Dell PowerEdge FN I/O Module Command Line Reference Guide 9.10(0.0)

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hash-algorithm seed

Select the seed value for the ECMP, LAG, and NH hashing algorithm.

Syntax

hash-algorithm seed value [linecard slot] [port-set number]

Parameters

seed value	Enter the keyword `seed` then the seed value. The range is from 0 to 4095.
linecard slot	Enter the keyword `linecard` then the linecard slot number.
port-set number	Enter the keywords `port-set` then the linecard port-pipe number.

Defaults

none

Command Modes

CONFIGURATION

Supported Modes

Full–Switch

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.