Ch.1 – WANs and Routers

CCNA 2 version 3.0

Rick Graziani

Cabrillo College

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Overview

Students completing this module should be able to:

• Identify organizations responsible for WAN standards

• Explain the difference between a WAN and LAN and the type of addresses each uses

• Describe the role of a router in a WAN

• Identify internal components of the router and describe their functions

• Describe the physical characteristics of the router

• Identify common ports on a router

• Properly connect Ethernet, serial WAN, and console ports

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Introduction to WANs

These are the major characteristics of WANs: • They connect devices that are separated by wide geographical areas. • They use the services of carriers such as the Regional Bell Operating

Companies (RBOCs), Sprint, MCI, VPM Internet Services, Inc., and Altantes.net.

• They use serial connections of various types to access bandwidth over large geographic areas.

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Introduction to WANs

• Routers offer many services, including internetworking and WAN interface ports. • Switches in the WAN provide connectivity for voice, data, and video

communication. • Modems include interface voice-grade services, channel service units/digital

service units (CSU/DSUs) that interface T1/E1 services, and Terminal Adapters/Network Termination 1 (TA/NT1s) that interface Integrated Services Digital Network (ISDN) services.

• Communication servers concentrate dial-in and dial-out user communication.

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Introduction to WANs

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Introduction to routers in a WAN

Routers connect and allow communication between two networks and determine the best path for data to travel through the connected networks.

RAM

• Stores routing tables

• Holds ARP cache

• Holds fast-switching cache

• Performs packet buffering (shared RAM)

• Maintains packet-hold queues

• Provides temporary memory for the configuration file of the router while the router is powered on

• Loses content when router is powered down or restarted

NVRAM

• Provides storage for the startup configuration file

• Retains content when router is powered down or restarted

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Introduction to routers in a WAN

Flash memory• Holds the operating system image (IOS) • Allows software to be updated without removing

and replacing chips on the processor • Retains content when router is powered down or

restarted • Can store multiple versions of IOS software • Is a type of electronically erasable,

programmable ROM (EEPROM) Read-only memory (ROM) has the following

characteristics and functions: • Maintains instructions for power-on self test

(POST) diagnostics • Stores bootstrap program and basic operating

system software • Requires replacing pluggable chips on the

motherboard for software upgrades

Interfaces • Connect router to network for

frame entry and exit • Can be on the motherboard

or on a separate module

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Router LANs and WANs

• Smaller broadcast domains

• Connecting Layer 3 networks

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Router LANs and WANs

• Routers are the backbone devices of large intranets and of the Internet.

• They operate at Layer 3 of the OSI model, making decisions based on network addresses.

• The two main functions of a router are the selection of best path for and the switching of frames to the proper interface.

• Routers accomplish this by building routing tables and exchanging network information with other routers.

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Router role in a WAN

• The WAN physical layer describes the interface between the data terminal equipment (DTE) and the data circuit-terminating equipment (DCE).

• Generally, the DCE is the service provider and the DTE is the attached device. In this model, the services offered to the DTE are made available through a modem or a CSU/DSU.

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Router role in a WAN

• The primary WAN roles of a router are therefore not routing, but providing connections to and between the various WAN physical and data-link standards.

• For example, a router may have an ISDN interface using PPP encapsulation and a serial interface terminating a T1 line using Frame Relay encapsulation.

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Academy approach to hands-on labs

• In the academy lab, devices that make up the WAN cloud are simulated by the connection between the back-to-back DTE-DCE cables.

• One of the routers will provide the clock rate (later).

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Router internal components

• CPU • RAM • Flash • NVRAM

• Buses • ROM • Interfaces • Power Supply

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Router physical characteristics

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Router external connections

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Management port connections

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Management port connections

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Connecting console interfaces

When connected using the console interface, the computer is acting as a “dumb terminal”.

<Router Output>

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Connecting console interfaces

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Connecting console interfaces

<Router Output>

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Connecting LAN interfaces

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Connecting WAN interfaces

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Connecting WAN interfaces

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Connecting WAN interfaces

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Summary

An understanding of the following key points should have been achieved:

• WAN and LAN concepts

• Role of a router in WANs and LANs

• WAN protocols

• Configuring encapsulation

• The identification and description of the internal components of a router

• The physical characteristics of a router

• The common ports on a router

• How to connect router console, LAN, and WAN ports