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Without VLANs, this coni guration would require three or more separate vSwitches, each
bound to a different physical adapter, and each physical adapter would need to be physically
connected to the correct network segment, as illustrated in Figure 5.24.
Figure 5.24
Supporting multiple
networks without
VLANs can increase
the number of
vSwitches, uplinks,
and cabling that is
required.
ESXi host
vSwitch0
vSwitch1
vSwitch2
vSwitch3
Management
network
vMotion
network
Production
network
Test/dev
network
Add in an IP-based storage network and a few more VM networks that need to be supported
and the number of required vSwitches and uplinks quickly grows. And this doesn't even take
uplink redundancy, for example NIC teaming, into account!
VLANs are the answer to this dilemma. Figure 5.25 shows the same network as in
Figure 5.24, but with VLANs this time.
While the reduction from Figure 5.24 to Figure 5.25 is only a single vSwitch and a single
uplink, you can easily add more VM networks to the coni guration in Figure 5.25 by simply
adding another port group with another VLAN ID. Blade servers provide an excellent example
of when VLANs offer tremendous benei t. Because of the small form factor of the blade cas-
ing, blade servers have historically offered limited expansion slots for physical network adapt-
ers. VLANs allow these blade servers to support more networks than they would be able to
otherwise.
No VLAN Needed
Virtual sw itches in the VMkernel do not need V L A Ns if an ESX i host has enough physical network
adapters to connect to each of the diff erent network segments. However, VLANs provide added fl ex-
ibility in adapting to future network changes, so the use of VLANs where possible is recommended.
As shown in Figure 5.25, VLANs are handled by coni guring different port groups within
a vSwitch. The relationship between VLANs and port groups is not a one-to-one relationship;
 
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