Compaq SW3323, SW3324, SW3322 manual Vlan Access Ports, 2Virtual Lans VLANs

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C-2Virtual Lans (VLANs)

If the switch is so configured, a unique VLAN identifier is placed in a tag appended to the packet when it is received by the switch from end-station nodes, if the packet does not already contain this information. The tag is then stripped off when the packets are forwarded to the destination end stations. Within the switch and between switches compliant with IEEE 802.1Q, these identifiers are used to control the destination of broadcast frames and to prevent flooding these broadcasts to all ports and connected interfaces.

Broadcast/multicast traffic from geographically dispersed stations can be directed across these links without radiating out to stations that are not part of the same VLAN. Up to 4094 different VLANs can be carried across these links, thus permitting the configuration of up to 4094 virtual workgroups. This approach is nonintrusive to end-station applications and the associated clients. You can configure VLANs using the VLAN Menu in the console interface and associated submenus, or via SNMP.

VLAN Access Ports

SW3322/SW3323/SW3324 ports can be configured as one of two types for the purpose VLAN configuration: access or hybrid. A VLAN access port is used to connect one or more VLAN-unaware devices into a port of a VLAN device. There can be no VLAN tagged frames entering an access port. If a tagged frame does arrive on an access port, the switch will drop the frame. You can configure a port as an access port (typically one connected to a VLAN-unaware end-user workstation) to ensure that it only receives untagged frames.

In the following example (Figure C-2), both ports are designated as access ports. The ports are both configured to be on VLAN X. The untagged frame (1) comes in through the left port and gets tagged with a VLAN X tag (2), based on the incoming port. As the frame comes out through the right side port, the tag is stripped (3) since the outgoing port is an access port as well and only accepts untagged frames. The incoming and outgoing frames can only propagate in this example because they are on the same VLAN.

Figure C-2VLAN Access Ports