9032947 Virtual LANs (VLANs) 85VLAN Egress PortsThe VLAN Egress Ports parameter is used to assign ports to a VLAN forcarrying VLAN tagged frames across a network. The assignment ofegress ports does not affect the assignment of VLAN IDs to framesentering the switch. However, frames exiting the switch may be sent outthe egress ports configured for a specific VLAN ID. Frames exiting theswitch via egress ports for a given VLAN are normally tagged.VLAN Access PortsIndividual ELS100-24TXG ports can be configured as one of two types forthe purpose of VLAN configuration: Access or Hybrid. A VLAN Accessport is used to connect one or more VLAN-unaware devices to the switch.VLAN tagged frames are not allowed to enter or exit an Access port. If atagged frame enters the switch on an Access port, the switch will drop theframe. End-user stations which do not support 802.1Q tags should beattached to ports on the switch configured as Access ports.In Example 1 in Figure D-2, both ports are designated as Access ports.The ports are both configured to be on VLAN X. An untagged frame (1)comes in through the left port and gets tagged with a VLAN X tag (2),based on the incoming port PVID. As the frame exits through the rightport, the tag is stripped (3) since the outgoing port is an Access port aswell and can only transmit untagged frames. The frame can propagatethrough the switch in this example only because both ports are on thesame VLAN.In Example 2 in Figure D-2, both ports are also Access ports, however theport on the left is on VLAN X while the port on the right on VLAN Y. Theuntagged frame (1) comes in through the left port and again gets taggedwith a VLAN X tag (2). However, because the outgoing port is on adifferent VLAN (VLAN Y), the frame is dropped. In general, frames cannotpropagate between ports unless both ports belong to the same VLAN.Figure D-2. VLAN Access Ports
