Tier 0 gateway A Tier 0 gateway has downlink connections to Tier 1 gateways and uplink connections to physical networks. The Tier 0 gateway provides a gateway service between the logical and physical network. The Tier 0 gateway enables route redistribution, routing, and BGP, as well as optional T0 services. The interfaces for this gateway connect the physical edge hosts to each ToR switch using the uplink segments described in the Segments topic. In the VMware NSX-T Data Center for VxBlock System design, by default, there is one Tier 0 gateway to handle the T0-GW-1 traffic. T0-GW-1 uses BGP and ECMP to link the nodes to the Cisco Nexus 9000 Series ToR switches. The following figure shows the North-South routing for the Tier 0 gateway in the design: Parent topic Edge ECMP topologyIn VMware NSX-T Data Center for VxBlock Systems, ECMP provides load-balancing across multiple paths northbound from the T0s to the Cisco Nexus 9000 Series ToR switches. VMware NSX-T Data Center supports a maximum of eight paths per edge node cluster.