Hirschmann MS30, Power MICE, MACH 4000, OCTOPUS, User Manual

Page: 123 / 196

Traffic control
Layer 2 Enhanced with Layer 2 Professional
Release 1.0 10/05
8.6 VLANs
121
VLANs are based on logical (instead of physical) links and are flexible
elements in the network design. The biggest advantage of VLANs is the
possibility of forming user groups based on the participant function and not
on their physical location or medium.
Since broad/multicast data packets are transmitted exclusively within a
virtual LAN, the remaining data network is unaffected.
The VLAN function is defined in the IEEE 802.1Q standard. The maximum
number of VLANs is limited by the structure of the VLAN tag
(see Fig. 36) to
4094.
Key words often used in association with VLANs are:
U
Ingress Rule
The ingress rules stipulate how incoming data is to be handled by the
Switch.
U
Egress Rule
The egress rules stipulate how outgoing data is to be handled by the
Switch.
U
VLAN identifier
The assignment to a VLAN is effected via a VLAN ID. Every VLAN exi-
sting in a network is identified by an ID. This ID must be unique, i.e.
every ID may only be assigned once in the network.
U
Port VLAN identifier (PVID)
The management assigns a VLAN ID for every port. It is known, there-
fore, as the port VLAN ID.
The Switch adds a tag to every data packet received with no tag. This tag
contains a valid VLAN ID.
When a data packet is received with a priority tag the Switch adds the
port VLAN ID.