Reference Guide

354 | Equal Cost Multi-Path (ECMP)
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Configuring Hash Algorithm Seed
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 means that for a given flow, even though the prefixes are sorted, two unrelated
chassis will 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.
Link Bundle Monitoring
Link Bundle Monitoring is supported on the S5000 switch.
Monitoring linked ECMP bundles allows traffic distribution amounts in a link to be monitored for unfair
distribution at any given time. A default
threshold of 60% is defined as an acceptable amount of traffic on
a member link. Links are monitored in 15-second intervals for three consecutive instances. Any deviation
within that time causes a syslog to be sent and an alarm event to be generated. When the deviation clears,
another syslog is sent and a clear alarm event is generated.
Enable IPv6 Deterministic ECMP Next
Hop.
ipv6 ecmp-deterministic
CONFIGURATION
Note: Packet loss might occur when you enable
ip/ipv6 ecmp-deterministic for the first-time only.
Note: While the seed is stored separately on each port-pipe, the same seed is used across all CAMs.
Note: You cannot separate LAG and ECMP, but you can use different algorithms across chassis with the
same seed. If LAG member ports span multiple port-pipes and stack units, set the seed to the same value
on each port-pipe to achieve deterministic behavior.
Note: If the hash algorithm configuration is removed. Hash seed will not go to original factory default
setting.
Task Command Syntax Command Mode
Specify the hash algorithm seed.
hash-algorithm seed value [stack-unit number]
[
port-set number]
Range: 0 to 447483646.
CONFIGURATION
Message 1
Link bundle monitoring percent threshold
%STKUNIT0-M:CP %IFMGR-5-BUNDLE_UNEVEN_DISTRIBUTION: Found uneven distribution in LAG bundle 11.
Task Command Syntax Command Mode