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Network Virtualization

Cumulus Linux supports these forms of network virtualization:

VXLAN (Virtual Extensible LAN), is a standard overlay protocol that abstracts logical virtual networks from the physical network underneath. You can deploy simple and scalable layer 3 Clos architectures while extending layer 2 segments over that layer 3 network.

VXLAN uses a VLAN-like encapsulation technique to encapsulate MAC-based layer 2 Ethernet frames within layer 3 UDP packets. Each virtual network is a VXLAN logical L2 segment. VXLAN scales to 16 million segments - a 24-bit VXLAN network identifier (VNI ID) in the VXLAN header - for multi-tenancy.

Hosts on a given virtual network are joined together through an overlay protocol that initiates and terminates tunnels at the edge of the multi-tenant network, typically the hypervisor vSwitch or top of rack. These edge points are the VXLAN tunnel end points (VTEP).

Cumulus Linux can initiate and terminate VTEPs in hardware and supports wire-rate VXLAN with Tomahawk, Trident II+ and Trident II platforms. VXLAN provides an efficient hashing scheme across IP fabric during the encapsulation process; the source UDP port is unique, with the hash based on L2-L4 information from the original frame. The UDP destination port is the standard port 4789.

Cumulus Linux includes the native Linux VXLAN kernel support and integrates with controller-based overlay solutions like VMware NSX and Midokura MidoNet.

VXLAN is supported only on switches in the Cumulus Linux HCL using Tomahawk, Trident II+ and Trident II chipsets.

VXLAN encapsulation over layer 3 subinterfaces is not supported. Therefore, VXLAN uplinks should be only configured as layer 3 interfaces without any subinterfaces.

Furthermore the VXLAN tunnel endpoints cannot share a common subnet; there must be at least one layer 3 hop between the VXLAN source and destination.


  • brctl

  • bridge fdb

  • ip link

  • ovs-pki

  • ovsdb-client

  • vtep-ctl

Useful Links