Vxlan Tunnel Endpoint - Cisco Nexus 7000 Series Configuration Manual

Overview

VXLAN Tunnel Endpoint

VXLAN uses VXLAN tunnel endpoint (VTEP) devices to map tenants' end devices to VXLAN segments
and to perform VXLAN encapsulation and de-encapsulation. Each VTEP function has two interfaces: One
is a switch interface on the local LAN segment to support local endpoint communication through bridging,
and the other is an IP interface to the transport IP network.
The IP interface has a unique IP address that identifies the VTEP device on the transport IP network known
as the infrastructure VLAN. The VTEP device uses this IP address to encapsulate Ethernet frames and transmits
the encapsulated packets to the transport network through the IP interface. A VTEP device also discovers the
remote VTEPs for its VXLAN segments and learns remote MAC Address-to-VTEP mappings through its IP
interface.
The VXLAN segments are independent of the underlying network topology; conversely, the underlying IP
network between VTEPs is independent of the VXLAN overlay. It routes the encapsulated packets based on
the outer IP address header, which has the initiating VTEP as the source IP address and the terminating VTEP
as the destination IP address.
Virtual Network Identifier (VNI)
In RFC 4364 L3VPNs, a 20-bit MPLS label that is assigned to a VPN route determines the forwarding behavior
in the data plane for traffic following that route. These labels also serve to distinguish the packets of one VPN
from another.
On the other hand, the various IP overlay encapsulations support a virtual network identifier (VNI) as part of
their encapsulation format.
A VNI is a value that at a minimum can identify a specific virtual network in the data plane. It is typically a
24- bit value which can support up to 16 million individual network segments.
There are two useful requirements regarding the scope of these VNIs.
• Network-wide scoped VNIs
• Locally assigned VNIs
Depending on the provisioning mechanism used within a network domain such as a data center, the VNI
may have a network scope, where the same value is used to identify the specific Layer-3 virtual network
across all network edge devices where this virtual network is instantiated. This network scope is useful
in environments such as within the data center where networks can be automatically provisioned by
central orchestration systems.
Having a uniform VNI per VPN is a simple approach, while also easing network operations (i.e.
troubleshooting). It also means simplifies requirements on network edge devices, both physical and
virtual devices. A critical requirement for this type of approach is to have a very large amount of network
identifier values given the network-wide scope.
In an alternative approach supported as per RFC 4364, the identifier has local significance to the network
edge device that advertises the route. In this case, the virtual network scale impact is determined on a
per node basis, versus a network basis.
When it is locally scoped, and uses the same existing semantics of a MPLS VPN label, the same
forwarding behaviors as specified in RFC 4364 can be employed. It thus allows a seamless stitching
together of a VPN that spans both an IP based network overlay and a MPLS VPN.
Cisco Nexus 7000 Series NX-OS VXLAN Configuration Guide
VXLAN Tunnel Endpoint
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