Dell PowerConnect M6220, User Configuration Manual

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Configuring VLANs
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• General — General ports can act like access or trunk ports or a hybrid of
both.
VLAN membership rules that apply to a port are based on the switchport
mode configured for the port. Table 21-2 shows the behavior of the three
switchport modes.
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 M6220, M6348, M8024, and M8024-k 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.
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.
Table 21-2. Switchport Mode Behavior
Mode VLAN Membership Frames
Accepted Frames Sent Ingress
Filtering
Access One VLAN Untagged Untagged Always On
Trunk All VLANs that exist
in the system
Tagged Tagged Always On
General As many as desired Tagged or
Untagged
Tagged or
Untagged
On or Off
NOTE:
A stack of switches behaves as a single switch, so VLAN tagging is not
required for packets traversing different stack members.