84 Virtual LANs (VLANs) ELS100-24TX
If the ELS100-24TX is so configured, and, if the frame does not already
contain a tag, a VLAN identifier is placed in a tag which is appended to
frames as they are received by the switch. With in the swit ch and betwe en
switches compliant with IEEE 802.1Q, th ese identifie rs are used to control
the destination of broadcast frames, preventing them from being flooded
to all connected stations and interfa ces. When frame s are forwarde d back
to destination end stations, the tag may or may not be stripped off,
depending on the configuration of the end station and the switch port.
By using 802.1Q tagged VLANs, users from physically dispersed
locations can be formed into gr oups by assigni ng them to s pecifi c VLANs.
Broadcast and multicast traffic for these specific VLANs can be directed
across the network without being radiated out to stations that are not
members of the same VLANs. Up to 4094 different VLANs can be
specified by the 802.1Q tag, thus permitting the configuration of up to
4094 virtual workgroups. This implementation is nonintrusive to end-
station applications and the associated clients.
ELS100-24TX VLAN Configuration
VLAN operation on the ELS100-24TX is disabled by default. When
VLANs are enabled, all frames are transfer red internally throug h the
switch with a VLAN tag . This tag may already be on the frame entering
the switch, or added to the frame by the swi tch. VLAN i nformatio n already
existing on frames e n t ering the switch is aut omatically handled by the
switch. The ELS100-24TX learns VLAN information from tagged frames
and appropriately switches frames out the proper ports based on this
information. The co nf iguration of VLANs f o r frames entering the switch
without tags must be m a de by the user of the swi t ch. This configurati o n
can be made either through the VLAN Menu in the console interface or
via SNMP. The paramet ers used to configur e V LANs on the ELS100-
24TX are explained below.

VLAN ID

The VLAN ID is used to uniquely identify different VLANs on a network.
The VLAN ID information is contained in the 802.1Q tag header on a
frame, and so identifies the VLAN to whi ch a frame b elongs. The ELS100-
24TX recognizes VLAN IDs in the tags on fr ames ente ring the s witch, and
can also add tags with an appropriate VLAN ID to untagged frames.

Ports in VLAN

When configuring VLAN s on the ELS100-24TX, in dividual ports are
assigned to specific VLANs by setting the Port VLAN ID (PVID) for each
port. Frames entering the switch which are untagged are automatically
assigned a VLAN ID by the switch based on the PVID of the incoming
port. The Ports in VLAN parameter makes the assignment of ports to
PVIDs. An individual port can on l y be as si gn ed to a single PVID with this
parameter.