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Chapter 2: Bridging Configuration Guide
Subnet-Based VLANs
Subnet-based VLANs are a subset of protocol-based VLANs and determine the VLAN of
a frame based on the subnet to which the frame belongs. To do this, the switch must look
into the network layer header of the incoming frame. This type of VLAN behaves
similarly to a router by segregating different subnets into different broadcast domains.
Policy-Based VLANs
Policy-based VLANs are the most general definition of VLANs. Each incoming
(untagged) frame is looked up in a policy database, which determines the VLAN to which
the frame belongs. For example, you could set up a policy that creates a special VLAN for
all email traffic between the management officers of a company so that this traffic will not
be seen anywhere else.
IA VLAN Support
The IA supports the following VLANs:
•
Port-based
•
Protocol-based
•
Subnet-based
When using the IA as a Layer-2 bridge/switch, use the port-based and protocol-based
VLAN types. When using the IA as a combined switch and router, use the subnet-based
VLANs in addition to port-based and protocol-based VLANs. It is not necessary to
remember the types of VLANs in order to configure the IA, as seen in the section on
configuring the IA.
VLANs and the IA
VLANs are an integral part of the IA family of switching routers. The IA switching routers
can function as Layer-2 switches as well as fully functional Layer-3 routers. Hence, they
can be viewed as a switch and a router in one box. To provide maximum performance and
functionality, the Layer-2 and Layer-3 aspects of the IA switching routers are tightly
coupled.
The IA can be used purely as a Layer-2 switch. Frames arriving at any port are bridged
and not routed. In this case, setting up VLANs and associating ports with VLANs is all
that is required. You can set up the IA switching router to use port-based VLANs,
protocol-based VLANs, or a mixture of the two types.
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Internet Appliance User Reference Manual
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