User`s manual

EDS-P510 Series Featured Functions
3-47
Communication between VLANs
If devices connected to a VLAN need to communicate to devices on a different VLAN, a router or Layer 3
switching device with connections to both VLANs needs to be installed. Communication between VLANs can
only take place if they are all connected to a routing or Layer 3 switching device.
VLANs: Tagged and Untagged Membership
The EDS-P510 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 the EDS-P510,
while inter-switch connections will be tagged members of all VLANs, defined as “Trunk Port” in the EDS-P510.
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.
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 to which VLAN. To communicate between
VLANs, a router must be used.
The EDS-P510 supports two types of VLAN port settings:
• Access Port: The port connects to a single device that is not tagged. The user must define the default port
PVID that determines to which VLAN the device belongs. Once the ingress packet of this Access Port
egresses to another Trunk Port (the port needs all packets to carry tag information), the EDS-P510 will
insert this PVID into this packet to help the next 802.1Q VLAN switch recognize it.
• Trunk 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-P510
Port 3 (Trunk Port, PVID 1)
VLAN 5 Untagged Device
VLAN 3 Untagged
Device
VLAN 4 Untagged
Device
VLAN 5 Untagged Device
VLAN 2 Untagged
Device
VLAN 4 Tagged Device, VID 4
VLAN 3 Tagged Device, VID 3
VLAN 2 Untagged
Device
VLAN 2 Untagged
Device
Device A Switch A Switch B
Device C
Device B
Device D
Device E
Device F
Device G
Device H
Device I
Port 1 (Access Port
PVID 5)
Port 7 (Access Port
PVID 4)
Port 5 (Access Port
PVID 3)
Port 4 (Access
Port PVID 2)
Port 2 (Trunk Port PVID 2,
Fixed VLAN (Tagged)=3,4)
Port 6 (Access Port PVID 5)
HUB
PWR1
PWR2
FAULT
7
6
5
4
3
2
1
G1
G2
G1
G3
G2
G3
EDS-P510
MASTER
G3
G2
G1
COUPLER
10/100/1000
7
6
5
4
3
2
1
10/100
EtherDevice Switch
Turbo
Ring
PoE
PWR1
PWR2
FAULT
7
6
5
4
3
2
1
G1
G2
G1
G3
G2
G3
EDS-P510
MASTER
G3
G2
G1
COUPLER
10/100/1000
7
6
5
4
3
2
1
10/100
EtherDevice Switch
Turbo
Ring
PoE