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, to achieve deterministic behavior, set the seed to the same
value on each port-pipe.
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 generate. When the
deviation clears, another syslog is sent and a clear alarm event generates. For example, link bundle monitoring percent threshold:
%STKUNIT0-M:CP %IFMGR-5-BUNDLE_UNEVEN_DISTRIBUTION: Found uneven distribution in LAG bundle
11.
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, you can specify interfaces. If you enable monitoring for the ECMP group, utilization calculation performs 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 you congure 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, to enable the link bundle monitoring feature, use the ecmp-group command. In the
following example, 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]
Gi 1/1 Up 36
Gi 1/1 Up 52
Managing ECMP Group Paths
To avoid path degeneration, congure the maximum number of paths for an ECMP route that the L3 CAM can hold. 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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