User`s guide

SET UP
Page 40 User’s guide ref 9018809-01 XSRING+ SHDSL switch
14 VLAN
14.1 Overview
VLAN function
The VLAN technology conform to the IEEE 802.1Q norm makes possible to transmit up to 4096
Ethernet networks over the same physical Ethernet layer.
The devices belonging to the same Ethernet VLAN can exchange Ethernet frames with one another
but cannot exchange frames with devices belonging to another VLAN except if a level 3 switch or an
equivalent device makes possible to bridge that VLANs.
Ethernet ports
When we speak of an Ethernet port of an XSRING+, we speak not only of 10/100 BT Ethernet ports,
but also of the SHDSL ports.
All SHDSL ports are supposed to be a unique SHDSL port.
Principles of operations
A particular field of each Ethernet frame stores the VLAN identity (VID) to which the frame belongs.
When that field stores the VLAN ID, one says the frame is tagged.
How are Ethernet frames tagged and untagged ?
An Ethernet frame can be tagged by the device which produces it.
Otherwise, the Ethernet frame is tagged by the switch to which the device is connected.
Reciprocally, the VLAN ID of an Ethernet frame can be removed by the Ethernet switch before being
transmitted to the Ethernet device or can be transmitted tagged to the device.
The switch filters the Ethernet frames according to their VLAN ID
When they come into the switch on an Ethernet port, Ethernet frames are tagged with the VLAN ID
assigned to that Ethernet port.
When it is received by the switch, a tagged Ethernet frame can only come out to an Ethernet port, if
the VLAN ID assigned to that port is the same as the VLAN ID of the Ethernet frame.
Html administration server and the serial gateway
If the VLAN function is enabled, Ethernet frames produced by the html administration server and the
serial gateway are tagged with a particular VLAN.
If the html administration server and the serial gateway do not belong to the same VLAN, a separate
IP address must be assigned to the serial gateway
Setting up the VLAN function
The VLAN set up is divided in two parts : The Egress policy set up and the Ingress policy set up.
The Egress policy consists in registering the authorised VLAN IDs and defining which Ethernet
ports belong to each VLAN.
The Ingress policy consists in defining which process must be applied to each Ethernet frames
going into the switch :
Tagging the frame with a VLAN ID or leaving the frames untagged etc …