Reference Guide

Term heading Description heading
but if the default algorithm does not provide satisfactory distribution of traffic, 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.
Related Commands load-balance (C-Series and S-Series)
hash-algorithm seed
Select the seed value for the ECMP, LAG, and NH hashing algorithm.
S4820T
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 keyword port-set then the linecard port-pipe number.
Defaults none
Command Modes CONFIGURATION
Command History
This guide is platform-specific. For command information about other platforms, refer to the
relevant FTOS Command Line Reference Guide .
The following is a list of the FTOS version history for this command.
Version 8.3.19.0 Introduced on the S4820T.
Version 8.3.11.1 Introduced on the Z9000.
Version 8.3.7.0 Introduced on the S4810.
Version 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.
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