Service Manual

Dell Networking OS provides a command line interface (CLI)-based solution for modifying the hash seed to ensure that on each
congured system, the ECMP selection is same. When congured, the same seed is set for ECMP, LAG, and NH, and is used for
incoming trac 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 dierent 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.
NOTE: If you remove the hash algorithm conguration, the hash seed does not return to the original factory default
setting.
To congure the hash algorithm seed, use the following command.
• Specify the hash algorithm seed.
CONFIGURATION mode.
hash-algorithm seed value [stack—unit number] [port-set number]
The range is from 0 to 4095.
Link Bundle Monitoring
Monitoring linked ECMP bundles allows trac distribution amounts in a link to be monitored for unfair distribution at any given time.
A default threshold of 60% is dened as an acceptable amount of trac 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. for example Link bundle monitoring percent
threshold %STKUNIT0-M:CP %IFMGR-5-BUNDLE_UNEVEN_DISTRIBUTION: Found uneven distribution in LAG
bundle 11..
The link bundle utilization is calculated as the total bandwidth of all links divided by the total bytes-per-second of all links. Within each
ECMP group, interfaces can be specied. If monitoring is enabled for the ECMP group, the utilization calculation is performed when
the utilization of the link-bundle (not a link within a bundle) exceeds 60%.
Enable link bundle monitoring using the ecmp-group command.
NOTE: An ecmp-group index is generated automatically for each unique ecmp-group when the user congures multipath
routes to the same network. The system can generate a maximum of 512 unique ecmp-groups. The ecmp-group indexes
are generated in even numbers (0, 2, 4, 6... 1022) and are for information only.
For link bundle monitoring with ECMP, the ecmp-group command is used to enable the link bundle monitoring feature. The ecmp-
group with id 2, enabled for link bundle monitoring is user congured. This is dierent from the ecmp-group index 2 that is created by
conguring routes and is automatically generated.
These two ecmp-groups are not related in any way.
Example of Viewing Link Bundle Monitoring
Dell# show link-bundle-distribution ecmp-group 1
Link-bundle trigger threshold - 60
ECMP bundle - 1 Utilization[In Percent] - 44 Alarm State - Active
Interface Line Protocol Utilization[In Percent]
Te 1/1/1 Up 36
Te 1/1/1 Up 52
Managing ECMP Group Paths
Congure the maximum number of paths for an ECMP route that the L3 CAM can hold to avoid path degeneration. When you do
not congure the maximum number of routes, the CAM can hold a maximum ECMP per route.
Equal Cost Multi-Path (ECMP)
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