MDS213 Datasheet, PDF (54/120 Pages) Zarlink Semiconductor Inc – 12-Port 10/100Mbps + 1Gbps Ethernet Switch

MDS213
Data Sheet
14.0 Virtual Local Area Networks (VLAN)
14.1 Introduction
A Virtual LAN (VLAN) is a logical, independent workgroup within a network. The members in this workgroup
communicate as if they are sharing the same physical LAN segment. VLANs are not limited by the hardware
constraints that physically connect traditional LAN segments to a network. As a result, VLANs can define a network
into multiple logical configurations.
14.2 VLAN Implementation
The MDS213 based VLAN implementation allows up to 256 VLANs in one switch. By using explicit or implicit VLAN
tagging and the GARP/GVRP protocol (defined in IEEE 802.1p and 802.1Q), VLANs may span across multiple
switches. A MAC address can belong to multiple VLANs, and a switch port may be associated with multiple VLANs.
14.2.1 Static Definitions of VLAN Membership
The MDS213 defines VLAN membership based on ports. Port based VLANs are organized by physical port
numbers. For example, switch ports 1, 2, 4, and 6 can be one VLAN, while ports 3, 5, 7, and 8 can be another
VLAN. Broadcasts from servers within each group would only go to the members of its own VLAN. This ensures
that broadcast storms cannot cause a network meltdown due to traffic volume.
14.2.2 Dynamic Learning of VLAN Membership
While port based VLAN only defines static binding between a VLAN and its port members, the MDS213's
forwarding decision needs to be based on the following:
• A destination MAC address and its associated port ID for a unicast frame, or
• The associated VLAN of a source MAC address, if the destination MAC address is unknown or it is a
multicast/broadcast frame. To make valid forwarding and flooding decisions, the MDS213 learns the
relationship of the MAC address to its associated port number and VLAN ID and builds up the internal
Switching Database at run-time for further use.
14.2.3 Dynamic Learning of Remote VLAN
In addition to adding and deleting VLAN member ports through network management tools statically, a MDS213
based switch can also support GVRP (GARP VLAN Registration Protocol). GVRP allows for dynamic registration of
VLAN port members within a switch and across multiple switches. In addition to supporting the dynamic update of
registration entries in a switch, GVRP is also used to communicate VLAN registration information to other VLAN-
aware switches, so that a VLAN member can be covered by a wide range of switches in a network. GVRP allows
both VLAN-aware workstations and switches to issue and revoke VLAN memberships. VLAN-aware switches
register and propagate VLAN membership to all ports belonging to the active topology of the VLAN.
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