36 | Rapier Switch User Guide |
indicating whether a VLAN is up or down, is passed to the Internet Protocol (IP) module. IP uses this information to determine route availability.
By default the switch is configured to include all ports as untagged members of a single default VLAN, with no VLAN tagging required on incoming frames, or added to outgoing frames. This default VLAN cannot be deleted from the switch. If all the devices on the physical LAN are to belong to the same logical LAN, that is, the same broadcast domain, then the default settings will be acceptable, and no additional VLAN configuration is required.
The ability to decouple logical broadcast domains from the physical wiring topology offers several advantages, which include:
■Workstations can be grouped logically or functionally, regardless of their physical location on the network.
■VLAN memberships can be changed at any time by software configuration, without moving the workstations physically, or by simply moving a cable from one port to another.
■By using VLAN tagging, network servers or other network resources can be shared between different work groups without losing data isolation or security.
■One port on the switch can be configured as an uplink to another 802.1Q- compatible switch. By using VLAN tagging, this one port can carry traffic from all VLANs on the switch. (With port based VLANs, one uplink port is required to uplink each VLAN to another switch.)
VLANs can consist of simple logical groupings of untagged ports, in which the ports receive and transmit untagged packets. Alternatively, VLANs can include tagged ports, which add VLAN tags to packets they transmit. A port can transmit either untagged packets or VLAN tagged packets to a VLAN of which it is a member, but not both. A port can be tagged for more than one VLAN, so that a single port can be used to uplink several VLANs to another compatible switch.
A VLAN can contain a mixture of VLAN tagged and untagged ports.
The switch is VLAN aware, in that it can accept VLAN tagged frames, and supports the VLAN switching required by such tags. A network can contain a mixture of VLAN aware devices, for instance other 802.1Q compatible switches, and VLAN unaware devices, for instance, workstations and legacy switches that do not support VLAN tagging. The switch can be configured to send VLAN tagged or untagged frames on each port, depending on whether or not the devices connected to the port are VLAN aware. By assigning a port to two different VLANs, to one as an untagged port and to another as a tagged port, it is possible for the port to transmit both
A port can belong to only one Spanning Tree entity (STP), and STP membership is per VLAN. A port cannot be added to a VLAN that is in a different STP from the VLANs to which the port already belongs, with one exception. The exception is that an untagged port in the default VLAN, that is not tagged for any other VLANs, can be moved from the default VLAN to any other VLAN in any STP.
Rapier Switch Software Release 2.2.1
