6.0.3

Table Of Contents
VLANs let you segment a physical network so that two machines in the network are unable to transmit
packets back and forth unless they are part of the same VLAN. For example, accounting records and
transactions are among a company’s most sensitive internal information. In a company whose sales,
shipping, and accounting employees all use virtual machines in the same physical network, you might
protect the virtual machines for the accounting department by seing up VLANs.
Figure 81. Sample VLAN Layout
Host 1
Standard Switch
Standard Switch
VM6 VM7 VM8
VM3 VM4 VM5
Standard Switch
VM9 VM10 VM11
Standard Switch
VM12
VLAN
B
VM13
VLAN
A
VM14
VLAN
B
VLAN A
VLAN B
Broadcast
Domain A
Broadcast
Domain B
Broadcast
Domain A and B
Multiple VLANs
on the same
virtual switch
Standard Switch
VM0 VM1 VM2
Host 3
Host 4
Host 2
Router
Switch 1
Switch 2
In this conguration, all employees in the accounting department use virtual machines in VLAN A and the
employees in sales use virtual machines in VLAN B.
The router forwards packets containing accounting data to the switches. These packets are tagged for
distribution to VLAN A only. Therefore, the data is conned to Broadcast Domain A and cannot be routed
to Broadcast Domain B unless the router is congured to do so.
This VLAN conguration prevents the sales force from intercepting packets destined for the accounting
department. It also prevents the accounting department from receiving packets intended for the sales group.
The virtual machines serviced by a single virtual switch can be in dierent VLANs.
Security Considerations for VLANs
The way you set up VLANs to secure parts of a network depends on factors such as the guest operating
system and the way your network equipment is congured.
ESXi features a complete IEEE 802.1q-compliant VLAN implementation. VMware cannot make specic
recommendations on how to set up VLANs, but there are factors to consider when using a VLAN
deployment as part of your security enforcement policy.
Chapter 8 Securing vSphere Networking
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