Equal cost multi-path (ECMP) routing protocol increases the north and south communication bandwidth by adding an uplink to the tier-0 logical router and configure it for each Edge node in an Edge cluster. The ECMP routing paths are used to load balance traffic and provide fault tolerance for failed paths.

ECMP paths are automatically created from the VMs attached to logical switches to the Edge nodes on which the tier-0 logical router is instantiated. A maximum of eight ECMP paths are supported.

Figure 1. ECMP Routing Topology
Equal cost multi-path routing with two uplinks to the tier-0 logical router of each Edge nose in a cluster.

For example, the topology shows two tier-0 logical routers in an edge cluster. Each tier-0 logical router is in an edge node and these nodes are part of the cluster. The uplink ports and define how the transport node connects to the logical switch to gain access to the physical network. When the ECMP routing paths are enabled these paths connect the VMs attached to logical switches and the two Edge nodes in the Edge cluster. The multiple ECMP routing paths increase the network throughput and resiliency.