Dell PowerConnect 7048P User Manual - Page 575

Table 21-2. Switchport Mode Behavior Mode Access Trunk General VLAN Membership Frames Accepted One VLAN Untagged All VLANs that exist Tagged in the system As many as desired Tagged or Untagged Frames Sent Untagged Tagged Ingress Filtering Always On Always On Tagged or Untagged On or Off When a port is in General mode, all VLAN features are configurable. When ingress filtering is on, the frame is dropped if the port is not a member of the VLAN identified by the VLAN ID in the tag. If ingress filtering is off, all tagged frames are forwarded. The port decides whether to forward or drop the frame when the port receives the frame. VLAN Tagging PowerConnect 7000 Series switches support IEEE 802.1Q tagging. Ethernet frames on a tagged VLAN have a 4-byte VLAN tag in the header. VLAN tagging is required when a VLAN spans multiple switches, which is why trunk ports transmit and receive only tagged frames. NOTE: A stack of switches behaves as a single switch, so VLAN tagging is not required for packets traversing different stack members. Tagging may be required when a single port supports multiple devices that are members of different VLANs. For example, a single port might be connected to an IP phone, a PC, and a printer (the PC and printer are connected via ports on the IP phone). IP phones are typically configured to use a tagged VLAN for voice traffic, while the PC and printers typically use the untagged VLAN. When a port is added to a VLAN as an untagged member, untagged packets entering the switch are tagged with the PVID (also called the native VLAN) of the port. If the port is added to a VLAN as an untagged member, the port does not add a tag to a packet in that VLAN when it exits the port. Configuring VLANs 575