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CHAPTER 8
Configuring VLANs
This chapter explains VirtualLocal Area Networks (VLANs) in detail and provides
configuration instructions and examples. It contains the following sections:
■“Overview of VLANs” on page 67
■“Configuring VLANs in a Solaris Environment” on page 69
■“Configuring VLANs in a Linux Environment” on page 71
Withmultiple VLANs on an adapter, a server with a single adapter can have a
logical presence on multiple IP subnets. By default, 128 VLANs can be defined for
each VLAN-aware adapter on your server.However, this number can be increased
by changing the system parameters.
If your network does not require multiple VLANs, you can use the default
configuration, in which case no further configuration is necessary.

Overview of VLANs

VLANs enable you to split your physical LAN into logical subparts, providing an
essential tool for increasing the efficiency and flexibilityof your network.
VLANs are commonly used to separate groups of network users into manageable
broadcast domains, to create logical segmentation of workgroups, and to enforce
security policies among each logical segment. Each defined VLAN behaves as its
own separate network, with its traffic and broadcasts isolated fromthe others,
increasing the bandwidth efficiency within each logical group.
Although VLANs are commonly used to create individual broadcast domains
and/or separate IP subnets, it can be useful for a server to have a presence on more
than one VLAN simultaneously.Several Sun products support multiple VLANs on a
per port or per interface basis, allowing very flexible network configurations.
FIGURE8-1 shows an example network that uses VLANs.