User`s guide

DES-3226S Layer 2 Switch CLI Reference
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ASYMMETRIC VLANS COMMANDS
The DES-3226S supports Asymmetric VLANs implementation for more
efficient use of shared resources such as server or gateway devices. An
asymmetric VLAN can be set up to allow a server (or several servers) to
communicate with several clients through a single physical link on the switch.
At the same time however, the clients are not allowed to link to each other
directly. For example, asymmetric VLANs can be set up so that the network
email server can be accessed by all email clients. All email clients can send
and receive data packets through the port connected to the email server, but
they are not allowed to send and receive data to the remaining ports. The email
server can freely associate with all ports, that is, all clients connected to the
switch.
The key difference between conventional 802.1q VLAN implementation or
symmetric VLANs, and asymmetric VLANs is in how address mapping is
handled. Symmetric VLANs use separate address tables so there is no address
sharing between VLANs. Asymmetric VLANs can use a single, shared
address table. Address sharing however takes place in only one direction. In
the example above, the VLAN created for the port connected to the email
server has the entire address table at its disposal so that any address can be
mapped to its port (PVID).
This feature can be enabled with the following important restrictions:
• Asymmetric VLAN support is limited to standalone switches.
• Each participating port must be untagged.
• GVRP and IGMP Snooping are not supported