Overlay Tunnels - Virtual Extensible Local Area Network (VXLAN)

6 important questions on Overlay Tunnels - Virtual Extensible Local Area Network (VXLAN)

What are some problems traditional Layer 2 networks face?


1. Only 4000 vlans with 802.1Q
2. Very large MAC address tables with hundreds of thousands of VMs
3. STP Blocks links, large number of disabled links, which is unacceptable.
4. ECMP is not supported
5. Host Mobility is difficult to implement.   

What is important to note about the UDP port used by VXLAN?

The default destination port assigned by IANA is 4789, however Linux uses the default destination port of 8472.

What is the VXLAN Network Identifier?

The VXLAN Network Identifier or VNI is similar to the VLAN ID. However, the VNI is 24 bits which results in 16 million possible VXLAN segments commonly known as overlay networks.
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In VXLAN, what are VTEPs?

VTEP are VXLAN Tunnel EndPoints. VTEPs originate or terminate VXLAN tunnels and are in between the endpoints and the VXLAN network.

What are the 4 Control and Data planes supported by Cisco and when are they preferred?

1. VXLAN with Multicast underlay (Popular for data center and private cloud)
2. VXLAN with static unicast VXLAN tunnels
3. VXLAN with MP-BGP EVPN control plane (Popular for data center and private cloud)
4 VXLAN with LISP control plane (preferred for campus)

Cisco SD-Access is an example of VXLAN with the LISP control plane. What is interesting about LISP and VXLAN?

VXLAN originated from a Layer 2 LISP specification.

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