PLANET WGS3-24240 - Manual (Page 113)

User’s Manual of WGS3-24000 / WGS3-24240
113
Adding an IEEE802.1Q Tag
Dest. Addr. Src. Addr. Length/E. type Data Old CRC
Dest. Addr. Src. Addr. E. type Tag Length/E. type Data New CRC
Priority CFI VLAN ID
Port VLAN ID
Packets that are tagged (are carrying the 802.1Q VID information) can be transmitted from one 802.1Q compliant network
device to another with the VLAN information intact. This allows 802.1Q VLAN to span network devices (and indeed, the entire
network – if all network devices are 802.1Q compliant).
Every physical port on a switch has a PVID. 802.1Q ports are also assigned a PVID, for use within the switch. If no VLAN are
defined on the switch, all ports are then assigned to a default VLAN with a PVID equal to 1. Untagged packets are assigned the
PVID of the port on which they were received. Forwarding decisions are based upon this PVID, in so far as VLAN are
concerned. Tagged packets are forwarded according to the VID contained within the tag. Tagged packets are also assigned a
PVID, but the PVID is not used to make packet forwarding decisions, the VID is.
Tag-aware switches must keep a table to relate PVID within the switch to VID on the network. The switch will compare the VID
of a packet to be transmitted to the VID of the port that is to transmit the packet. If the two VID are different the switch will drop
the packet. Because of the existence of the PVID for untagged packets and the VID for tagged packets, tag-aware and
tag-unaware network devices can coexist on the same network.
A switch port can have only one PVID, but can have as many VID as the switch has memory in its VLAN table to store them.
Because some devices on a network may be tag-unaware, a decision must be made at each port on a tag-aware device before
packets are transmitted – should the packet to be transmitted have a tag or not? If the transmitting port is connected to a
tag-unaware device, the packet should be untagged. If the transmitting port is connected to a tag-aware device, the packet
should be tagged.
Default VLANs
The Switch initially configures one VLAN, VID = 1, called "default." The factory default setting assigns all ports on the Switch to
the "default". As new VLAN are configured in Port-based mode, their respective member ports are removed from the "default."
VLAN and Link aggregation Groups
In order to use VLAN segmentation in conjunction with port link aggregation groups, you can first set the port link aggregation
group(s), and then you may configure VLAN settings. If you wish to change the port link aggregation grouping with VLAN
already in place, you will not need to reconfigure the VLAN settings after changing the port link aggregation group settings.
VLAN settings will automatically change in conjunction with the change of the port link aggregation group settings
4.3.1.1 VLAN Configuration
802.1Q VLAN Configuration
There are up to 4041 configurable VLAN groups. By default when 802.1Q is enabled, all ports on the switch belong to default
Original Ethernet
New Tagged Packet