Dell PowerSwitch S4128F-ON OS10 Enterprise Edition User Guide Release 10.4.3.0 - Page 684

Enable overlay routing between virtual networks The previous sections described how a VTEP switches traffic between hosts within the same L2 tenant segment, the virtual network, and transports traffic over an IP underlay fabric. This section describes how a VTEP enables hosts in different L2 segments belonging to the same tenant VRF communicate with each other. NOTE: On the S4248-ON switch, IPv6 overlay routing between virtual networks is not supported with static VXLAN. IPv6 overlay routing is, however, supported with BGP EVPN. Each tenant is assigned a VRF and each virtual-network interface is assigned an IP subnet in the tenant VRF. The VTEP acts as the L3 gateway that routes traffic from one tenant subnet to another in the overlay before encapsulating it in the VXLAN header and transporting it over the IP underlay fabric. To enable host traffic routing between virtual networks, configure an interface for each virtual network and associate it to a tenant VRF. Assign a unique IP address in the IP subnet range associated with the virtual network to each virtual-network interface on each VTEP. To enable efficient traffic forwarding on a VTEP, OS10 supports distributed gateway routing. A distributed gateway means that multiple VTEPs act as the gateway router for a tenant subnet. The VTEP nearest to a host acts as its gateway router. To support seamless migration of hosts and virtual machines on different VTEPs, configure a common virtual IP address, an anycast IP address, on all VTEPs for each virtual network. Use this anycast IP address as the gateway IP address on VMs. To support multiple tenants when each tenant has its own L2 segments, configure a different IP VRF for each tenant. All tenants share the same VXLAN underlay IP fabric in the default VRF. 1 Create a non-default VRF instance for overlay routing in Configuration mode. For multi-tenancy, create a VRF instance for each tenant. ip vrf tenant-vrf-name exit 2 Configure the anycast gateway MAC address all VTEPs use in all VXLAN virtual networks in Configuration mode. When a VM sends an Address Resolution Protocol (ARP) request for the anycast gateway IP address in a VXLAN virtual network, the nearest VTEP responds with the configured anycast MAC address. Configure the same MAC address on all VTEPs so that the anycast gateway MAC address remains the same if a VM migrates to a different VTEP. Because the configured MAC address is automatically used for all VXLAN virtual networks, configure it in global Configuration mode. ip virtual-router mac-address mac-address 3 Configure a virtual-network interface, assign it to the tenant VRF, and configure an IP address. The interface IP address must be unique on each VTEP, including VTEPs in VLT pairs. You can configure an IPv6 address on the virtual-network interface. Different virtual-network interfaces you configure on the same VTEP must have virtual-network IP addresses in different subnets. If you do not assign the virtual-network interface to a tenant VRF, it is assigned to the default VRF. interface virtual-network vn-id ip vrf forwarding tenant-vrf-name ip address ip-address/mask no shutdown exit 4 Configure an anycast gateway IPv4 or IPv6 address for each virtual network in INTERFACE-VIRTUAL-NETWORK mode. This anycast IP address must be in the same subnet as the IP address of the virtual-network interface in Step 3. Configure the same IPv4 or IPv6 address as the anycast IP address on all VTEPs in a virtual network. All hosts use the anycast gateway IP address as the default gateway IP address in the subnet that connects to the virtual-network interface configured in Step 3. Configure the anycast gateway IP address on all downstream VMs. Using the same anycast gateway IP address allows host VMs to move from one VTEP to another VTEP in a VXLAN. Dell EMC recommends using an anycast gateway in both VLT and non-VLT VXLAN configurations. interface virtual-network vn-id ip virtual-router address ip-address 684 VXLAN