Equal-Cost Multi-Path in NSX-T Data Center

You can configure Equal-Cost Multi-Path (ECMP) routing on ESXi hosts that have Enhanced Network Stack (ENS) enabled.

The ECMP 5-tuple feature (hashing on protocol number, source and destination address, and source and destination port) is disabled by default in ESXi. You can enable it by setting the parameter lb_ecmp to true with the following API call:

PUT https://<nsx-manager>/policy/api/v1/infra/connectivity-global-config
{
    "lb_ecmp": true,
    ...
}

You can see the current lb_ecmp value with the API GET https://<nsx-manager>/policy/api/v1/infra/connectivity-global-config.

Notes about 5-tuple ECMP:

• When 5-tuple ECMP for ESXi is enabled, it will be applied to all ESXi hosts. Only hosts that have ENS enabled will work properly.
• Do not enable this feature if you have non-ENS hosts, or a mix of ENS and non-ENS hosts.
• When 5-tuple ECMP is enabled, ENS-enabled hosts will consume significantly more flows. When the flow limit is reached, the performance of the host might be impacted.
• Certain topologies, such as a load balancer, where layer 3 does not provide enough path diversity, might benefit more with 5-tuple ECMP enabled.