Connectivity Guide
Enable overlay routing between virtual networks
The previous sections described how a VTEP switches trac between hosts within the same L2 tenant segment, the virtual network, and
transports trac over an IP underlay fabric. This section describes how a VTEP enables hosts in dierent 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 trac 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 trac routing between virtual networks, congure 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 ecient trac 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 dierent VTEPs, congure 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, congure a dierent 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 Conguration mode. For multi-tenancy, create a VRF instance for each
tenant.
ip vrf tenant-vrf-name
exit
2 Congure the anycast gateway MAC address all VTEPs use in all VXLAN virtual networks in Conguration 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 congured anycast MAC address. Congure the same MAC address on all VTEPs so that the
anycast gateway MAC address remains the same if a VM migrates to a dierent VTEP. Because the congured MAC address is
automatically used for all VXLAN virtual networks, congure it in global Conguration mode.
ip virtual-router mac-address mac-address
3 Congure a virtual-network interface, assign it to the tenant VRF, and congure an IP address.
The interface IP address must be unique on each VTEP, including VTEPs in VLT pairs. You can congure an IPv6 address on the
virtual-network interface. Dierent virtual-network interfaces you congure on the same VTEP must have virtual-network IP
addresses in dierent 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 Congure 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.
Congure 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 congured in Step
3. Congure 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 congurations.
interface virtual-network vn-id
ip virtual-router address ip-address
684
VXLAN