Chapter 5: Layer 2 Fundamentals; Layer 2 Switching And Bridging; Mac Bridging - Avaya 2330 Manual

Chapter 5: Layer 2 fundamentals

Ethernet is one of the most widely deployed Layer 2 Local Area Network (LAN) transport technologies
today. A LAN is a data communications network connecting terminals, computers, and printers within a
building or other geographically limited area. Advantages of Ethernet include:
• Ability to scale in bandwidth and speed — Ethernet switches support high port densities and
forwarding rates in the millions of packets per second
• Support of Class of Service (CoS) that allows up to eight classes of service to be defined
• Ease of deploying multipoint communications
The Avaya Secure Router 2330/4134 Ethernet Layer 2 features support VLAN MAC bridging of traffic
within the LAN, and between LAN to WAN for traffic in and out of the carrier network. The Secure Router
2330/4134 platform uses both the hardware network processor and software forwarding logic for Ethernet
Layer 2 switching. The network processor handles LAN switching. Software forwarding works with the
network processor to achieve LAN to WAN (and WAN to LAN) data switching. The Secure Router
2330/4134 also supports termination of Layer 3 traffic on a VLAN to achieve routing using the Layer 3
engine.

Layer 2 switching and bridging

Local Area Network (LAN) is a data communications network connecting terminals, computers
and printers within a building or other geographically limited areas. These devices could be
connected through wired cables or wireless links. Ethernet and Token Ring are examples of
standard LAN technologies. LAN switching involves examining physical network addresses
that uniquely identify a device in the network.
LAN bridging offers an extension of the LAN by supporting the connection of multiple LAN
segments. MAC addresses of the datagram that flow through bridges are examined to build a
table of known destinations. If the destination of a datagram is on the same segment as the
source of the datagram, the bridge drops the datagram because forwarding is not required.
However, if the destination is on another segment, the bridge transmits the datagram on that
segment only. If the bridge does not know the destination segment, it transmits the datagram
on all segments except the source segment (a technique known as flooding).

MAC bridging

MAC Bridging allows multiple LANs to be connected together. Transparent bridging involves
the creation of MAC address tables, and limits the Ethernet collision domain by filtering data
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