Enterasys Networks 700 - Manual (Page 81)

Managing the Module 2-61
The MultiSwitch 700 Device View
What Is A VLAN?
A Virtual Local Area Network (VLAN) is a logical group of devices that function
as a single Local Area Network segment (broadcast domain). Devices comprising
a VLAN may be (physically) widely separated, allowing users located in separate
areas or connected to separate ports to belong to a single VLAN group. Users
assigned to a VLAN can send and receive broadcast and multicast traffic as
though they were all physically connected to a single network segment.
VLAN-capable switches isolate broadcast and multicast traffic received from
VLAN groups, and contain broadcasts and multicasts from members of a VLAN
within that group.
What Is An 802.1Q Port-Based VLAN?
Switches that support the pre-standard IEEE 802.1Q draft specification for
port-based VLANs act by classifying frames into VLAN membership. Usually,
VLAN classification is based on tag headers (VLAN tags) in the headers of data
frames. The tag header is inserted into the frame directly after the Source MAC
address field. A four-byte field in the tag header is used as the VLAN identifier.
These VLAN tags are added to data frames by the switch as the frames are
transmitted and/or received by certain ports, and are later used to make
forwarding decisions by the switch and other 802.1Q switches. In the absence of a
VLAN tag, a frame is assigned VLAN membership according to the VLAN
configuration of the switch port that receives the frame.
About 802.1Q VLAN Configuration and Operation
An 802.1Q VLAN is defined by assigning it a unique identification number (the
VLAN ID) and an optional name. The VLAN ID is used to identify data frames
that originate from, and are intended for, the ports assigned to the VLAN. Up to
64 VLANs may be created, with VLAN IDs ranging from 2-4094. VLAN ID 1 is
reserved for the Default VLAN.
NOTES
For older versions of MultiSwitch 700 firmware, if 802.1Q is to be utilized it is required
that all modules in the chassis be configured to operate in 802.1Q mode. Distributed
Chassis Management may not be supported for MultiSwitch 700 modules operating in
802.1Q mode. In such cases, it is recommended that all modules installed in the
MultiSwitch 700 chassis be configured via Local Management to operate in Standalone
mode. Contact the Global Technical Assistance Center for firmware upgrade information.
NOTE
For current versions of MultiSwitch 700 firmware, DELHF-UA modules cannot be
installed in a MultiSwitch 700 that is operating in 802.1Q mode. This will be corrected in
a future version of firmware.