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Layer 1
This is referred to as the physical layer. It handles the
electrical connections and signaling required to make a
physical link from one point in the network to another. It is
on this layer that the unique Media Access Control (MAC)
address is defined.
Layer 2
This layer, commonly called the switching layer, allows end
station addressing and the establishment of connections
between them.
Layer 2 switching forwards packets based on the unique
MAC address of each end station and offers high-
performance, dedicated-bandwidth of Fast or Gigibit
Ethernet within the network.
Layer 2 does not ordinarily extend beyond the intranet. To
connect to the Internet usually requires a router and a
modem or other device to connect to an Internet Service
Provider's WAN. These are Layer 3 functions.
Layer 3
Commonly referred to as the routing layer, this layer
provides logical partitioning of networks (subnetting),
scalability, security, and Quality of Service (QoS).
The backbone of the Internet is built using Layer 3 functions.
IP is the premier Layer 3 protocol.
IP is itself, only one protocol in the IP protocol suite. More
extensive capabilities are found in the other protocols of the
IP suite. For example; the Domain Name System (DNS)
associates IP addresses with text names, the Dynamic Host
Configuration Protocol (DCHP) eases the administration of
IP addresses, and routing protocols such as the Routing
Information Protocol (RIP), the Open Shortest Path First
(OSPF), and the Border Gateway Protocol (BGP) enable
Layer 3 devices to direct data traffic to the intended
148 VH-2402-L3 Management Guide
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