In legacy cisco environment we can only create 4094 Vlans as
it only uses 12 bits Vlan id. If we talk about cloud infrastructure where there
are many clients.
Do we think 4094 vlan are sufficient?
Answer is NO.
We certainly need a large number of vlan or similar
technique to provide Layer 2 isolation. Cisco worked with vendors like VM, citrix
etc. and developed a layer 2 technique known as VXLAN. It uses 24 segment id which comes out to be 16 million segments. This unique segment ID is called
VXLAN network identifier(VNID).
VXLAN is a way to send Layer 2 traffic over L3 network. L3
can be shared by various other vendors and gives more flexibility from
deployment prospective.
It is also known as MAC in UDP technique as it encapsulates
Layer 2 frame in Layer 3 UDP packet.
Not only it divide the layer 2 network in large number of
isolated network but it also enable us to use all the uplink called ECMP ( equal
cost multipath) as it uses L3 routing table which is not possible is Legacy STP
environment.
This technique is not available in legacy catalyst switches.
Cisco nexus 9000,5672UP and 56128P are capable of VXLAN and most suitable product for large Datacenters
and other cloud infrastructures.
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