Cabletron Systems SmartSTACK ELS100-24TXM Installation And User Manual

Also see for SmartSTACK 100 ELS100-24TXM: User guide addendum

Contents

90 Virtual LANs (VLANs) ELS100-24TXMIf the ELS100-24TXM is so configured, and, if the frame does not alreadycontain a tag, a VLAN identifier is placed in a tag which is appended toframes as they are received by the switch. Within the switch and betweenswitches compliant with IEEE 802.1Q, these identifiers are used to controlthe destination of broadcast frames, preventing them from being floodedto all connected stations and interfaces. When frames are forwarded backto 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 dispersedlocations can be formed into groups by assigning them to specific VLANs.Broadcast and multicast traffic for these specific VLANs can be directedacross the network without being radiated out to stations that are notmembers of the same VLANs. Up to 4094 different VLANs can bespecified by the 802.1Q tag, thus permitting the configuration of up to4094 virtual workgroups. This implementation is nonintrusive to end-station applications and the associated clients.ELS100-24TXM VLAN ConfigurationVLAN operation on the ELS100-24TXM is disabled by default. WhenVLANs are enabled, all frames are transferred internally through theswitch with a VLAN tag. This tag may already be on the frame enteringthe switch, or added to the frame by the switch. VLAN information alreadyexisting on frames entering the switch is automatically handled by theswitch. The ELS100-24TXM learns VLAN information from tagged framesand appropriately switches frames out the proper ports based on thisinformation. The configuration of VLANs for frames entering the switchwithout tags must be made by the user of the switch. This configurationcan be made either through the VLAN Menu in the console interface orvia SNMP. The parameters used to configure VLANs on theELS100-24TXM are explained below.VLAN IDThe 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 aframe, and so identifies the VLAN to which a frame belongs. TheELS100-24TXM recognizes VLAN IDs in the tags on frames entering theswitch, and can also add tags with an appropriate VLAN ID to untaggedframes.Ports in VLANWhen configuring VLANs on the ELS100-24TXM, individual ports areassigned to specific VLANs by setting the Port VLAN ID (PVID) for eachport. Frames entering the switch which are untagged are automaticallyassigned a VLAN ID by the switch based on the PVID of the incomingport. The Ports in VLAN parameter makes the assignment of ports toPVIDs. An individual port can only be assigned to a single PVID with thisparameter.