Cabletron Systems SmartSTACK ELS10-27TX Supplement Manual

Contents

A-1APPENDIX AVIRTUAL LANS (VLANS)A.1 VLANS AND FRAME TAGGINGThe ELS10-27TX supports IEEE 802.1Q-compliant virtual LANs (VLANs). Thiscapability provides a highly efficient architecture for establishing VLANs within anetwork and for controlling broadcast/multicast traffic between workgroups.Central to this capability is an explicit frame tagging approach for carrying VLANinformation between interconnected network devices.With frame tagging, a four-byte data tag field is appended to frames that cross thenetwork. The tag identifies which VLAN the frame belongs to. The tag may beadded to the frame by the end station itself or by a network device, such as a switch.In the example in Figure A-1 below, the workstations attached to the top switch aremembers of the same two VLANs as the workstations attached to the bottomswitch. The 802.1Q tags are used to carry VLAN information in the framestraveling between the two switches.* Note is true if it does not have a tag and is a hybrid port, or the port is anaccess port.* Note is only stripped, if the hybrid port and the tag in the packet matches thePVID or is an access port.Figure A-1. Two-Switch VLAN Configuration2X 4X 6X 8X 10X 12X 14X 16X 18X 20X 22X 24X2627RESETELS10-27TXEPIM100PWRCPUETHERNET SWITCH25X 26X 27X10BASE-T/100BASE-TXCOMLINKSTATUSLINKSTATUSLINKSTATUSLINKSTATUSLINKSTATUSLINKSTATUSLINKSTATUSLINKSTATUSLINKSTATUSLINKSTATUSLINKSTATUSLINKSTATUSLINKSTATUSLINKSTATUSLINKSTATUSPORT STATUS MODESTATUSTX ACT FDX MONRX COL 100 USR2X 4X 6X 8X 10X 12X 14X 16X 18X 20X 22X 24X2627RESETELS10-27TXEPIM100PWRCPUETHERNET SWITCH25X 26X 27X10BASE-T/100BASE-TXCOMLINKSTATUSLINKSTATUSLINKSTATUSLINKSTATUSLINKSTATUSLINKSTATUSLINKSTATUSLINKSTATUSLINKSTATUSLINKSTATUSLINKSTATUSLINKSTATUSLINKSTATUSLINKSTATUSLINKSTATUSPORT STATUS MODESTATUSTX ACT FDX MONRX COL 100 USRVLAN YVLAN Y802.1Q tag addedby Incoming port*802.1Q tag carriesVLAN Identifier802.1Q used byswitch to determineVLAN, then strippedby forwarding port*123VLAN XVLAN X13