Administrator Guide

Version Description
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.
The system 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.
ip ecmp-group
Enable and specify the maximum number of ecmp that the L3 CAM hold for a route, By default, when maximum paths are not configured,
the CAM can hold a maximum of 16 ecmp per route.
C9000 Series
Syntax
ip ecmp-group {maximum-paths | {number} {path-fallback}
To negate a command, use the no ip ecmp-group maximum-paths {number} command.
Parameters
maximum-paths Specify the maximum number of ECMP for a route. The range is 2 to 64.
path-fallback Use the keywords path-fallback to enable this feature. If you enable the feature, re-
enter this keyword to disable the feature.
Defaults 16
Command Modes CONFIGURATION
Command History
Version Description
9.9(0.0) Introduced on the C9010.
9.2(1.0) Introduced on the Z9500.
9.0.0.0 Introduced on the Z9000.
8.3.10.0 Introduced on the S4810.
Usage Information You must save the new ECMP settings to the startup-config (write-mem) then reload the system for the new
settings to take effect.
Related
Commands
show ip cam linecard – Display content-addressable memory (CAM) entries for a set of ports on a line card.
626 Equal Cost Multi-Path (ECMP)