Moxa Technologies user manual Sample Applications of VLANs using Moxa EDS-726, Hub

EDS-726 Series User’s Manual Featured Functions

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.

MOXA EDS-726 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 needs all packets to carry tag information), EDS-726 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 MOXA EDS-726

Device A

VLAN 5 Untagged Device

Port 1 (Access Port

PVID 5)

	Port 7 (Access Port	Device I
	PVID 4)	VLAN 4 Untagged
Switch A	Switch B
		Device

Port 3 (Trunk Port, PVID 1)	Port 5 (Access Port
	PVID 3)	Device H
		VLAN 3 Untagged
Port 2 (Trunk Port PVID 2,		Device
Fixed VLAN (Tagged)=3,4)

HUB

Port 4 (Access	Port 6 (Access Port PVID 5)
Port PVID 2)

Device F

VLAN 2 Untagged	Device G
Device	VLAN 5 Untagged Device

Device E

VLAN 4 Tagged Device, VID 4

Device B	Device C	Device D
VLAN 2 Untagged		VLAN 3 Tagged Device, VID 3
Device	VLAN 2 Untagged
	Device

In this application,

yPort 1 connects a single untagged device and assigns it to VLAN 5; it should be configured as “Access Port” with PVID 5.

yPort 2 connects a LAN with two untagged devices belonging to VLAN 2. One tagged device with VID 3 and one tagged device with VID 4. It should be configured as “Trunk Port” with PVID 2 for untagged device and Fixed VLAN (Tagged) with 3 and 4 for tagged device. Since each port can only have one unique PVID, all untagged devices on the same port can only belong to the same VLAN.

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