Vxlan Packet Format; Vxlan Tunnel Endpoint - Cisco ASR 9000 Series Configuration Manuallines

Implementing VXLAN
• BGP does not work with VXLAN anycast feature within a data center.
• IGP works on the underlay network within a data center.
• BGP and IGP should be used on the WAN side.
• Data center top-of-rack (TOR) switches to use static routes between router customer IP to the anycast
Requirement to deploy VxLAN Anycast Gateway
Since the multicast group is used for mirroring the control frames, in case of IPv6 neighbor advertisements,
the duplicate address detection (DAD) protocol will bring down the service because the same addresses are
detected between two routers (or interface). Hence you must disable IPv6 DAD on the BVI interface and
enable unsolicited node detection (ND) responses.

VXLAN Packet Format

VXLAN defines a MAC-in-UDP encapsulation scheme where the original Layer 2 frame has a VXLAN
header added and is then placed in a UDP-IP packet. With this MAC-in-UDP encapsulation, VXLAN tunnels
Layer 2 network over Layer 3 network. The VXLAN packet format is shown in the following figure.
Figure 67: VXLAN Packet Format
As shown in the above figure, VXLAN introduces an 8-byte VXLAN header that consists of a 24-bit VNID
and a few reserved bits. The VXLAN header together with the original Ethernet frame goes in the UDP
payload. The 24-bit VNID is used to identify Layer 2 segments and to maintain Layer 2 isolation between
the segments. With all 24 bits in VNID, VXLAN can support approx 16 million LAN segments.

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.
gateway.
L2VPN and Ethernet Services Configuration Guide for Cisco ASR 9000 Series Routers, IOS XR Release 6.3.x
VXLAN Packet Format
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