WANs and Router Basics Semester 2 Chapter 2: WANs & Routers Chapter 3: Router CLI By: Allan Johnson

WANs and Router Basics

Semester 2Chapter 2: WANs & Routers

Chapter 3: Router CLI

By: Allan Johnson

Table of ContentsTable of Contents

WAN Devices

WAN Standards

WAN Technologies

Router Basics

Router User Interface

WAN Devices

Table of Contents

WAN ServicesWAN Services

WANs provide for the exchange of data packets/frames between routers/bridges and the LANs they support.

A WAN interconnects LANs that are usually separated by large geographic areas.

WANs connect devices. Such devices include...

RoutersRoutersRouters offer many services including:

InternetworkingWAN serial interfaces

Routers can operate as...Internal RoutersBackbone Routers Area Border RoutersAutonomous System Boundary Routers

WAN Bandwidth SwitchesWAN Bandwidth Switches

Service provider equipment that connects to WAN bandwidth for voice, data and video communications.

ModemsModems

Also called CSU/DSUs (channel service units/digital service units)

Interface with voice-grade connection in order to convert analog signal to digital.

Represents the DCE side of the DTE/DCE connection.

More on DTE/DCE later

Communication ServersCommunication Servers

Concentrates dial-in and dial-out services.Equipment is usually at the service provider’s

site.

WAN Standards

Table of Contents

WAN StandardsWAN Standards

What layers of the OSI model do WAN standards describe?

Physical and Data Link Layers

WAN Physical LayerWAN Physical Layer

Protocols that describe how to provide electrical, mechanical, operational, and functional connections for WAN services.

These services are most often obtained from WAN service providers such as RBOCs, alternate carriers, post-telephone, and telegraph (PTT) agencies.

Describes the interface between the data terminal equipment (DTE) and the data circuit-terminating equipment (DCE).


Typically, 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.


Several physical layer standards specifying this interface between the DTE & DCE are...

EIA/TIA-232 EIA/TIA-449 V.24 V.35 X.21 G.703 EIA-530

WAN Data-Link LayerWAN Data-Link Layer

WAN data link protocols describe how frames are carried between systems on a single data link.

They include protocols designed to operate over dedicated point-to-point, multipoint, and multi-access switched services.

WAN standards are defined and managed by a number of recognized authorities, including the following agencies: ITU-T, ISO, IETF, & EIA

WAN Data-Link EncapsulationsWAN Data-Link Encapsulations

High-Level Data Link Control (HDLC) Cisco default encapsulation; typically used between

routers running Cisco IOS; replacing SDLCStreamlined: no windowing or flow control may not be compatible with different vendors because

of the way each vendor has chosen to implement it. HDLC supports both point-to-point and multipoint

configurations with minimal overhead


Frame Relay uses high-quality digital facilities; uses simplified framing with no error correction

mechanisms (connectionless!!);it can send Layer 2 information much more rapidly

than other WAN protocols


PPP (Point-to-Point Protocol)Developed by IETF; replacing SLIPContains a field to identify the network layer protocolPPP can check for link quality during connection

establishmentSupports PAP (Password Authentication Protocol) &

CHAP (Challenge Handshake Authentication Protocol)

WAN Technologies

Table of Contents

WAN Technologies Overview


Dedicated• T1, E1, T3, E3• xDSL• SONET

Analog• Dial-up modems• Cable modems• Wireless

Switched

Circuit Switched

• POTS• ISDN

Packet Switched

• X.25• Frame Relay

Cell Switched• ATM• SMDS





Switched

Circuit Switched

• POTS• ISDN

Packet Switched



Dedicated Digital ServicesDedicated Digital Services

T series in U.S. and E series in EuropeUses time division multiplexing to “slice up” data and

assign time slots for transmissionsT1 = 1.544 MbpsT3 = 44.736 MbpsE1 = 2.048 MbpsE3 = 34.368 Mbps

•Uses twisted pair & fiber•Extremely popular•Moderate cost

Dedicated Digital Services provide full-time connectivity through a point-to-point link


Digital Subscriber Lines (xDSL); the x stands for a family of technologies

New WAN Technology for home use; decreasing bandwidth with increasing distance from the phone companies CO.

Data rates as high as 51.84 Mbps but more common to be in the 100s of Kbps

Varieties include HDSL, SDSL, ADSL, & VDSLModerate expense and getting cheaper


Synchronous Optical Network (SONET)Specialized high bandwidth technology for use at

various Optical Carrier speeds (OC) ranging from 51.84 Mbps (OC-1) to 9,952 Mbps (OC-192)

Uses lasers to divide the wavelength of the light into sections that can carry large amounts of data (Wave Division Multiplexing)

Very expensive; used by large ISPs and other Internet backbone entities.





Switched

Circuit Switched

• POTS• ISDN

Packet Switched



Analog ServicesAnalog Services

Dial-up Modems (switched analog)Limited to 56 kbpsWorks with existing phone networkLow cost and widespread usage


Cable Modems (Shared Analog)Puts data signals on the same cable as television

signalsIncreasing in popularity Maximum bandwidth can be 10 Mbps, though this

degrades as more users attach to a given network segment (behaving like an unswitched LAN)

Cost is relatively low; usage is small but increasing; the medium is coaxial cable.


TerrestrialBandwidths typically in the

11 Mbps range Cost is relatively lowLine-of-sight is usually

requiredUsage is moderate

SatelliteCan serve mobile users

and remote usersUsage is widespreadCost is very high

Wireless





Switched

Circuit Switched

• POTS• ISDN

Packet Switched



Circuit Switched ServicesCircuit Switched Services

Plain Old Telephone System (POTS)Not a computer data service but...

POTS is an important component of our communication infrastructure and

It is still the standard for designing reliable networks

Circuit Switched ServicesCircuit Switched Services

Integrated Services Digital Network (ISDN)Historically important--first dial-up digital serviceCost is moderate; max. bandwidth = 128 kbps for

BRI (Basic Rate Interface)2 B channels @ 64kps and 1 D channel @ 16kpsB channels are voice/data channels; D for signaling

B

B

D





Switched

Circuit Switched

• POTS• ISDN

Packet Switched



Packet Switched ServicesPacket Switched Services

X.25 (Connection-oriented)Older WAN technology developed in 1970sReliable--X.25 has been extensively debugged and

is now very stable--literally no errors in modern X.25 networks

Store & Forward--Since X.25 stores the whole frame to error check it before forwarding it on to the destination, it has an inherent delay (unlike Frame Relay) and requires large, expensive memory buffering capabilities.

Packet Switched ServicesPacket Switched Services

Frame Relay (Connectionless)More efficient and much faster than X.25Packet switched version of ISDN (which is circuit

switched); data rates up to 44.736Mbps with 56kbps and 384kbps being the most popular

Used mostly to forward LAN IP and IPX packets but can be used to forward other types of traffic

Primary competitive advantage is its low cost





Switched

Circuit Switched

• POTS• ISDN

Packet Switched



Cell Switched ServicesCell Switched ServicesAsynchronous Transfer Mode (ATM)

Relatively new WAN Technology related to broadband ISDN; max. bandwidth = 622 Mbps

Developed in order to provide one technology for both WANs and LANs to transport data, video, and voice. (High Cost)

Key Benefits:One network for all traffic--voice, data, videoCompatible with current wiring infrastructure (cable plant)Very flexible and scalableSimplifies network management

Cell Switched ServicesCell Switched Services

Switched Multimegabit Data Service (SMDS)Closely related to ATM; SMDS is the MAN

(Metropolitan Area Network) implementation of ATMHigh Cost with max. bandwidth 44.736 Mbps

Acronym Name Max. Bandwidth Comments

T1, T3 T1, T3 1.544 & 44.736 Mbps Widely used telecommunicationsxDSL Digital Subscriber Line 384 kbps New technology over phone lines

SONETSynchronous Optical Network

9,992 Mbps Very fast optical fiber transmission

Dial-up Modem Modem 56 kbps Mature technology over phone lines

Cable Modem Cable Modem 10 Mbps New technology using cable TV

Terrestrial Wireless Wireless 11 Mbps Microwave and laser links

Satellite Wireless Wireless 2 Mbps Microwave and laser links

POTSPlain Old Telephone Service

4 kHz Analog The Standard for Reliability

ISDNIntegrated Services Digital Network

128 kbps Data and Voice Together

X.25 X.25 An Old Reliable, WorkhorseFrame Relay Frame Relay up to 44.736 Mbps A flexible new workhorse; son of ISDN

ATMAsynchronous Transfer Mode

622 Mbps High powered Networks

SMDSSwitched Multimegabit Data Service

1.544 & 44.736 Mbps MAN variant of ATM

Cell Switched Services

Dedicated Digital Services

Analog Services

Circuit Switched Services

Packet Switched Services

WAN Technologies Review

Router Basics

Table of Contents

Internal ComponentsInternal Components

RAM NVRAM Flash ROM

InterfacesConsoleAuxiliary

RAMRAM

Temporary storage for router configuration filesRAM content is lost on power down or restartStores...

Routing tablesARP cacheFast switching cachePacket bufferingAnd Packet hold queues

NVRAMNVRAM

Non-volatile RAMStores backup/startup configuration filesContent is not lost when router is powered down

or restarted.

FlashFlash

EEPROM (Electronically Erasable Programmable Read-Only Memory)

Holds the Cisco IOS (Internet Operating System)Allows updating of software without replacing the

Flash chipMultiple versions of IOS can be storedRetained on power down

ROMROM

Contains POST (Power On Self Test)A bootstrap program (loads the Cisco IOS)And operating system software

Backup, trimmed down version of the IOSUpgrades require installing new chip set

InterfacesInterfaces

Network connections through which packets enter and exit the router

Attached to the motherboard or as separate modules.

LabsLabs

Before moving on to Ch. 3, make sure you have done both of the required labs for Ch. 2

Lab 2.2.2Lab 2.2.3.2

Router User Interface

Table of Contents

User EXEC ModesUser EXEC Modes

User modeLimited mode used for checking the routers status,

looking at routing tables, etc.You cannot configure the routerOnce you’ve typed the password to enter user mode,

you will see the > prompt. The word “Router” will be the name of the router.

Password:Router>

Means you’re in user mode

Privileged EXEC ModesPrivileged EXEC Modes

Privileged modeDoes everything User mode doesFull power to configure the routerIn user mode, you enter the command “enable” and

then the privileged password

Router> enablePassword:Router#

Means you’re in privileged mode

Command ListsCommand Lists

To get a list of commands available in either user mode or privileged mode, enter a ? at the prompt.

Router> ?Router# ?Since the available commands will be more than

the screen can hold, you will get the --More-- message at the bottom.

Hitting the space bar will advance the screen to show the next page.

ipflash:interfacesipxversionparser

Router# show ?

Getting Help on a Command

Getting Help on a Command

The ? can be used with a partial command to learn all the available commands that match what you entered.

To use this help feature, enter the partial command, then tap the space bar, then type ?

For example...

The Router returned all the available commands

for “show”

Error IndicatorError Indicator

When you’ve entered an error in the command string, a carat (^) symbol will indicate where the error occurred.

For example...

Router# show runing-config ^% Invalid input detected at the ‘^’ marker

LabsLabs

Before taking the Ch. 2/3 test, make sure you have done both of the required labs for Ch. 3

Lab 3.2.1Lab 3.2.2

End Slide Show

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WANs and Router Basics Semester 2 Chapter 2: WANs & Routers Chapter 3: Router CLI By: Allan Johnson