Vlans - Avaya 2330 Manual

Layer 2 fundamentals
sent between LAN segments. This reduces network congestion and allows networks to be
partitioned for administrative purposes.

VLANs

A Virtual LAN (VLAN) is a switched network that is logically segmented on an organizational
basis, by functions, project teams, or applications rather than on a physical or geographical
basis. VLAN segments the physical local-area network (LAN) infrastructure into different
subnets so that packets are switched only between ports within the same VLAN. Devices on
a VLAN are configured so that they can communicate as if they were attached to the same
physical wire, when in fact they are located on a number of different LAN segments. With VLAN
partitioning, traffic stays within the appropriate groups, minimizing wasteful broadcasts.
A VLAN is made up of a group of ports that define a logical broadcast domain. These ports
can belong to a single device, or they can be spread across multiple devices. In a VLAN-aware
device, every frame received on a port is classified as belonging to one and only one VLAN.
Whenever a broadcast, multicast, or unknown destination frame must be flooded by a VLAN-
aware device, the frame is sent out only through all the other active ports that are members of
this VLAN.
The default device configuration groups all ports into the port-based default VLAN 1. This VLAN
cannot be deleted from the system.
The Secure Router 2330/4134 supports port-based and protocol-based VLANs.
A port-based VLAN is a VLAN whose ports are explicitly configured as members. In port-based
VLANs, all ports are always static members. When creating a port-based VLAN, you assign a
VLAN identification number (VID) and specify which ports belong to the VLAN. The VID is used
to coordinate VLANs across multiple devices.
Protocol-based VLANs are an effective way to segment your network into broadcast domains
according to the network protocols in use. Traffic generated by any network protocol can be
automatically confined to its own VLAN.
VLAN tagging is a MAC option. A VLAN-tagged frame is a basic MAC data frame that has had
a 4-byte VLAN header inserted between the SA and Length/Type fields. The VLAN header
consists of the following fields:
• A reserved 2-byte type value, indicating that the frame is a VLAN frame
• Tag Protocol Identifier (TPID) - defined value of 8100 in hex. When a frame has the
EtherType equal to 8100, this frame carries the tag IEEE 802.1Q/802.1P.
• TCI - Tag Control Information field including user priority, Canonical format indicator and
VLAN ID.
VLAN tagging can be enabled or disabled on each interface.
The Secure Router 2330/4134 uses IEEE 802.1Q tagging of frames and coordinates VLANs
across multiple devices. The following figure shows the additional 4-octet (tag) header that is
inserted into a frame after the source address and before the frame type. The tag contains the
VLAN ID associated with the frame.
30 Configuration — Layer 2 Ethernet
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July 2013