3com 3CDSG8 User Guide
48
VLANS
If the network has adequate performance and security for your current needs, it is
recommended that you leave the VLAN settings in the default configuration. The default
configuration is as follows:
recommended that you leave the VLAN settings in the default configuration. The default
configuration is as follows:
• All ports are members of VLAN 1
• The switch management interface is on VLAN 1 (this cannot be changed)
• All ports have a Port VLAN ID (PVID) of 1
• All ports can send and receive both VLAN-tagged and untagged packets (i.e. they are
• The switch management interface is on VLAN 1 (this cannot be changed)
• All ports have a Port VLAN ID (PVID) of 1
• All ports can send and receive both VLAN-tagged and untagged packets (i.e. they are
"hybrid" ports)
In the default configuration, any port is able to send traffic to any other port and a PC
connected to any port will be able to reach the management interface. Broadcast traffic, for
example, will be flooded to all ports on the switch.
connected to any port will be able to reach the management interface. Broadcast traffic, for
example, will be flooded to all ports on the switch.
There are three different parameters that can be configured for each port on the switch; VLAN
IDs (VLAN membership), PVID and Packet Type. Note that the ports within a Trunk cannot be
configured individually; configure the Trunk instead (Trunks are labeled T1 to T4).
IDs (VLAN membership), PVID and Packet Type. Note that the ports within a Trunk cannot be
configured individually; configure the Trunk instead (Trunks are labeled T1 to T4).
7.1.2 VLAN IDs
• VLAN 1 is a special VLAN; it cannot be deleted and, if there is a possibility that a port
could become isolated, the Web User-interface will add the port to VLAN 1.
• You can add up to 64 VLANs to the configuration of the switch. Each VLAN must be
given a VLAN ID in the range 1-4094.
• A port can be a member of up to 64 VLANs.
• All packets travelling through the switch are associated with one and only one VLAN.
• If a port is not a member of a VLAN, it cannot send or receive packets associated with
• All packets travelling through the switch are associated with one and only one VLAN.
• If a port is not a member of a VLAN, it cannot send or receive packets associated with
that VLAN.
• A tagged packet carries its VLAN ID in the payload of the packet.
• An untagged packet, received on a port with Packet Type set to All, is associated with the
• An untagged packet, received on a port with Packet Type set to All, is associated with the
VLAN identified by the PVID.
7.1.3 PVID
• The PVID is (Port VLAN ID) is the VLAN ID that is associated with untagged, ingress
packets.
• It is not possible to remove a port from VLAN 1 unless its PVID has been changed to
something other than 1.
• Outgoing packets are tagged unless the packet's VLAN ID is the same as the PVID. When
the PVID is set to "None," all outgoing pacekts are tagged.
7.1.4 Packet Type
• PCs should be connected to ports with Packet Type set to All. PCs cannot, in general,
send or receive tagged packets.
• Switches should be connected to each other with Packet Type set to Tagged.
• If the Packet Type is set to All, the port can accept incoming tagged and untagged
• If the Packet Type is set to All, the port can accept incoming tagged and untagged
packets. Untagged packets will be associated with the VLAN identified by the PVID.
Tagged packets will be dropped unless the port is a member of the VLAN identified by
the VLAN tag in the packet. Outgoing packets will be tagged unless the packet's VLAN ID
is the same as the PVID.
Tagged packets will be dropped unless the port is a member of the VLAN identified by
the VLAN tag in the packet. Outgoing packets will be tagged unless the packet's VLAN ID
is the same as the PVID.