Moxa Technologies user manual Sample Applications of VLANs using PT-7728

Models: PT-7728

1 87
Download 87 pages 13.62 Kb
Page 55
Image 55

PT-7728 User’s Manual

Featured Functions

VLANs: Tagged and Untagged Membership

The PT-7728 supports 802.1Q VLAN tagging, a system that allows traffic for multiple VLANs to be carried on a single physical (backbone, trunk) link. When setting up VLANs you need to understand when to use untagged and tagged membership of VLANs. Simply put, if a port is on a single VLAN it can be an untagged member, but if the port needs to be a member of multiple VLANs, tagged membership must be defined.

A typical host (e.g., clients) will be untagged members of one VLAN, defined as Access Port in PT-7728, while inter-switch connections will be tagged members of all VLANs, defined as Trunk Port in PT-7728.

The IEEE Std 802.1Q-1998 defines how VLANs operate within an open packet-switched network. An 802.1Q compliant packet carries additional information that allows a switch to determine which VLAN the port belongs to. If a frame is carrying the additional information, it is known as a tagged frame.

To carry multiple VLANs across a single physical (backbone, trunk) link, each packet must be tagged with a VLAN identifier so that the switches can identify which packets belong in which VLAN. To communicate between VLANs, a router must be used.

The PT-7728 supports two types of VLAN port settings:

yAccess Port: The port connects to a single device that is not tagged. The user must define the default port PVID that assigns which VLAN the device belongs to. Once the ingress packet of this Access Port egresses to another Trunk Port (the port nePT all packets to carry tag information), PT-7728 will insert this PVID into this packet to help the next 802.1Q VLAN switch recognize it.

yTrunk Port: The port connects to a LAN that consists of untagged devices/tagged devices and/or switches and hubs. In general, the traffic of the Trunk Port must have a Tag. Users can also assign PVID to a Trunk Port. The untagged packet on the Trunk Port will be assigned the port default PVID as its VID.

The following section illustrates how to use these ports to set up different applications.

Sample Applications of VLANs using PT-7728

3-41

Page 55
Image 55
Moxa Technologies user manual Sample Applications of VLANs using PT-7728, VLANs Tagged and Untagged Membership