Command Reference Guide

500 | Equal Cost Multi-Path
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Parameters
Defaults
None
Command Modes
CONFIGURATION
Command
History
Usage
Information
Deterministic ECMP sorts ECMPs in order even though RTM provides them in a random
order. However, the hash algorithm uses as a d 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 d to ensure that on each
configured system, the ECMP selection is same. When configured, the same d is set for
ECMP, LAG, and NH, and is used for incoming traffic only.
ip ecmp-deterministic
e
Deterministic ECMP Next Hop arranges all ECMPs in order before writing them into the
CAM. For example, suppose the RTM learns 8 ECMPs in the order that the protocols and
interfaces came up. In this case, the FIB and CAM sort them so that the ECMPs are always
arranged.This implementation ensures that every chassis having the same prefixes orders the
ECMPs the same.
With 8 or less ECMPs, the ordering is lexicographic and deterministic. With more than 8
ECMPs, ordering is deterministic, but it is not in lexicographic order.
Syntax
ip ecmp-deterministic
Defaults
Disabled
Command Modes
CONFIGURATION
d value
Enter the keyword followed by the d value.
Range: 0 to 4095
linecard slot
Enter the keyword linecard followed by the linecard slot number.
port-set number
Enter the keyword port-set followed by the linecard port-pipe
number.
Version 8.3.1.0 Introduced on E-Series.
Note: While the d is stored separately on each port-pipe, the same d is used across
all CAMs.
Note: You cannot separate LAG and ECMP, but you can use different algorithms
across chassis with the same d. If LAG member ports span multiple port-pipes and
line cards, set the d to the same value on each port-pipe to achieve deterministic
behavior.
Note: If the hash algorithm configuration is removed. Hash d will not go to original
factory default setting.