VXLAN use case

[netstar-sg-service]

Hi,

I just read some documentation regarding VXLAN deployment in Nexus 9000.

One of the advantages of having VXLAN is more namespace (24bit) compare to VLAN(12bit). So it is said that VXLAN can have more than 16millions logical subnet.

How do we apply this in real deployment of Nexus 9000?

I can only saw that the vlan and vxlan is one to one mapping. For example:

vlan 10
 vn-segment 100010
vlan 20
 vn-segment 100020
vlan 30
 vn-segment 100030

So how can we achieve this 16 millions if the mapping is only one to one?

[Philip D'Ath]

Consider cases where the VXLAN never leaves the virtual environment.  You never need a VLAN.

Also some devices can terminate a VXLAN directly (like an ASA) without having to go to a VLAN.

[netstar-sg-service]

I haven't learned about VXLAN in virtual environment (like VMWare NSX). But I assume that the vswitch will apply the VXLAN directly to the individual port (something like switchport access vxlan). Is that correct?

So this particular use case will not be applicable to nexus 9k then since it is using one to one mapping between VXLAN and VLAN.

[Manish Gogna]

The guidelines and limitations for VXLAN are described in detail in the following link

http://www.cisco.com/c/en/us/td/docs/switches/datacenter/nexus9000/sw/6-x/vxlan/configuration/guide/b_Cisco_Nexus_9000_Series_NX-OS_VXLAN_Configuration_Guide/b_Cisco_Nexus_9000_Series_NX-OS_VXLAN_Configuration_Guide_chapter_010.html

Manish

[jkilleda]

VXLAN use case

It means that VLAN uses 12 bits VLAN ID to address layer 2 segments , which results in limited scalability of only 4094 VLANs. VXLAN uses a 24 bit segment ID known as the VXLAN network identifier, which enables up to 16 million VXLAN segments so we can go beyond 4094 L2 segments as compared to regular VLAN.

[Rick1776]

There is way more cooler things then more vlans. VxLAN will allow you to extend two data center with L2 over L3 (think of a better slicker version of OTV), it will allow the Gateway to live on every leaf switch (AnyCast Gateway) to know more routing, and one of the most important is that spanning-tree doesn't live in a VxLAN deployment.
So for all of the advantages more VLAN's is the least of my worries unless I'm an ISP. Most ISP will reuse VLAN 10 in a different VRF for a different customer with a different vn-segment number, that's where the power of VxLAN comes into play.

This is a good link that illustrates the above concepts
concept.https://www.cisco.com/c/en/us/td/docs/switches/datacenter/nexus9000/sw/7-x/vxlan/configuration/guide/b_Cisco_Nexus_9000_Series_NX-OS_VXLAN_Configuration_Guide_7x/b_Cisco_Nexus_9000_Series_NX-OS_VXLAN_Configuration_Guide_7x_chapter_0100.html