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Configuration Guide - IP Unicast Routing

CloudEngine 12800 and 12800E V200R002C50

This document describes the configurations of IP Unicast Routing, including IP Routing, Static Route, RIP, RIPng, OSPF, OSPFv3, IPv4 IS-IS, IPv6 IS-IS, BGP, Routing Policy, and PBR.

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Enable ECMP Load Balancing Consistency

Enable ECMP Load Balancing Consistency


Equal-Cost Multi-Path routing (ECMP) implements load balancing and link backup. ECMP applies to the network where multiple links to the same destination are available. In the traditional routing technology, packets are forwarded to the destination through one link only; the other links are in backup or inactive state; switching between these links requires a certain period when dynamic routes are used. Different from the traditional routing technology, ECMP can use multiple links to increase transmission bandwidth and transmit data on a faulty link without any delay or packet loss.

When one link of equal-cost multiple paths fails, all traffic needs to be load balanced again based on hash calculation. ECMP load balancing consistency, however, ensures that hash calculation is performed only for traffic on this faulty link, without affecting traffic on other normal links. This function ensures normal operation of services, in which sessions need to be maintained, on normal links.


  1. Run system-view

    The system view is displayed.

  2. Run load-balance ecmp stateful enable

    The ECMP load balancing consistency function is enabled.

    When configuring this function, pay attention to the following points:
    • To use this function, ensure that different destination addresses are reachable through the same or completely different equal-cost multiple paths.

    • After enabling this function, do not change the configured load balancing hash algorithm, hash algorithm offset, and load balancing mode. Otherwise, this function may be unable to take effect.

    • This function may be unable to take effect when outbound ports of equal-cost links are intermittently disconnected.
    • The ECMP load balancing consistency function only takes effect only for common IPv4 traffic, but not for traffic transmitted over tunnels.
    • The ECMP load balancing consistency function is unable to take effect for IPv6 traffic.

  3. Run commit

    The configuration is committed.

Verifying the Configuration

Run the display port forwarding-path { src-ip src-ip-data [ ip-mask-len | source-ip-mask ] | dst-ip dst-ip-data [ ip-mask-len | dst-ip-mask ] | src-mac src-mac-data | dst-mac dst-mac-data | protocol { protocol-number | gre | icmp | igmp | ip | ipinip | ospf | tcp [ l4-src-port src-port-data | l4-dst-port dst-port-data ]* | udp [ l4-src-port src-port-data | l4-dst-port dst-port-data ] * } } * [ enhanced ] command to check the outbound interface of packets that contain specified 5-tuple information, source MAC address, and destination MAC address.

Updated: 2019-03-21

Document ID: EDOC1000166601

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