Cabletron Systems SmartSwitch Router, Руководство пользователя

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Chapter 3: Bridging Configuration Guide
58 SmartSwitch Router User Reference Manual
Multicast-based VLANs
Multicast-based VLANs are created dynamically for multicast groups. Typically, each
multicast group corresponds to a different VLAN. This ensures that multicast frames are
received only by those ports that are connected to members of the appropriate multicast
group.
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 which 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.
SSR VLAN Support
The SSR supports:
• Port-based VLANs
• Protocol-based VLANs
• Subnet-based VLANs
When using the SSR as an L2 bridge/switch, use the port-based and protocol-based
VLAN types. When using the SSR 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 SSR, as seen in the section on
configuring the SSR.
VLANs and the SSR
VLANs are an integral part of the SSR family of switching routers. The SSR switching
routers can function as layer-2 (L2) switches as well as fully-functonal layer-3 (L3) routers.
Hence they can be viewed as a switch and a router in one box. To provide maximum
performance and functionality, the L2 and L3 aspects of the SSR switching routers are
tightly coupled.
The SSR can be used purely as an L2 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 SSR switching router to use port-based VLANs, protocol-
based VLANs, or a mixture of the two types.
The SSR can also be used purely as a router, i.e., each physical port of the SSR is a separate
routing interface. Packets received at any interface are routed and not bridged. In this
case, no VLAN configuration is required. Note that VLANs are still created implicitly by