Deployment Guide
Equal Cost Multi-Path (ECMP)
Dell Networking OS supports equal cost multi-path (ECMP).
ECMP for Flow-Based Anity
Dell Networking OS supports ECMP for ow-based anity.
NOTE: IPv6 /128 routes having multiple paths do not form ECMPs. The /128 route is treated as a host entry and nds its place in
the host table.
NOTE: Using XOR algorithms results in imbalanced loads across an ECMP/LAG when the number of members in said ECMP/LAG
is a multiple of 4.
Enabling Deterministic ECMP Next Hop
Deterministic ECMP next hop arranges all ECMPs in order before writing them into the content addressable memory (CAM).
For example, suppose the RTM learns eight ECMPs in the order that the protocols and interfaces came up. In this case, the forwarding
information base (FIB) and CAM sort them so that the ECMPs are always arranged. This implementation ensures that every chassis having
the same prexes orders the ECMPs the same.
With eight or less ECMPs, the ordering is lexicographic and deterministic. With more than eight ECMPs, ordering is deterministic, but it is
not in lexicographic order.
To enable deterministic ECMP next hop, use the appropriate command.
NOTE
: Packet loss might occur when you enable ip/ipv6 ecmp-deterministic for the rst-time only.
• Enable IPv4 Deterministic ECMP Next Hop.
CONFIGURATION mode.
ip ecmp-deterministic
• Enable IPv6 Deterministic ECMP Next Hop.
CONFIGURATION mode.
ipv6 ecmp-deterministic
Link Bundle Monitoring
Monitoring linked ECMP bundles allows trac distribution amounts in a link to be monitored for unfair distribution at any given time.
A threshold of 60% is dened as an acceptable amount of trac 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.
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, 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.
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