Cabletron Systems SmartSTACK ELS10-27TX Supplement Manual

Contents

A-2ELS10-27TX VLAN ConfigurationIf the ELS10-27TX is so configured, and, if the frame does not already contain atag, a VLAN identifier is placed in a tag which is appended to frames as they arereceived by the switch. Within the switch and between switches compliant withIEEE 802.1Q, these identifiers are used to control the destination of all frames,preventing them from being flooded to all connected stations and interfaces. Whenframes are forwarded to destination end stations, the tag may or may not bestripped off, depending on the configuration of the switch port.By using 802.1Q tagged VLANs, users from physically dispersed locations can beformed into groups by assigning them to specific VLANs. Broadcast, Unicast andmulticast traffic for these specific VLANs can be directed across the networkwithout being radiated out to stations that are not members of the same VLANs.Up to 32 different VLANs can be specified by the 802.1Q tag. Thisimplementation is non-intrusive to end-station applications and the associatedclients. Both tagged and non-tagged as defined can function properly in theenvironment.A.2 ELS10-27TX VLAN CONFIGURATIONVLAN operation on the ELS10-27TX is disabled by default.You must configureall VLANs, prior to using them. When VLANs are enabled, all frames aretransferred internally through the switch with a VLAN tag. This tag may alreadybe on the frame entering the switch, or it may be added to the frame by the switch.VLAN information already existing on frames entering the switch isautomatically handled by the switch. The ELS10-27TX uses VLAN informationfrom tagged frames and appropriately switches frames out the proper ports basedon this information. This configuration can be made either through the VLANMenu in the console interface or via SNMP. The parameters used to configureVLANs on the ELS10-27TX are explained below.If tag-unaware devices are to be supported, access ports and default VLAN IDsfor the ports must be configured.A.2.1 VLAN IDThe VLAN ID is used to uniquely identify different VLANs on a network. TheVLAN ID information is contained in the 802.1Q tag header on a frame, and soidentifies the VLAN to which a frame belongs. The ELS10-27TX recognizesVLAN IDs in the tags on frames entering the switch, and can also add tags withan appropriate VLAN ID to untagged frames.