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CCNA 2 v3.1 Module 1WANs & Routers

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Wide Area Network Characteristics

• It is a data communications network

• Connect devices separated by wide geographical area

state, province, or country

• Use the services of carrier providers

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

• Use serial connections to access bandwidth

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How do WANs differ from LANs

• WAN data connections across a broad geographic area

• connect company sites so that information can be exchanged between distant offices

• Interconnect LANs

• Exchange data packets and frames between routers and switches and the LANs they support

• What layer do WANs operate at

Datalink layer (2)

Physical layer (1)

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WAN Devices

• Routers

Connect two networks

Allow communication between two networks

Determine the best path for data to travel

• Switches provide connectivity for voice, data, and video

• Modems

Interface voice-grade services

Channel service units/digital service units (CSU/DSUs) that interface T1/E1 services

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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WAN DataLink layer Protocols

• Describe how frames are carried between systems on a single data link

• Protocols designed to operate over

Dedicated point-to-point link

Multipoint link

Multi-access switched services (Frame Relay)

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WAN Standards Authroities

• International Telecommunication Union-Telecommunication Standardization Sector (ITU-T)

formerly the Consultative Committee for International Telegraph and Telephone (CCITT)

• International Organization for Standardization (ISO)

• Internet Engineering Task Force (IETF)

• Electronic Industries Association (EIA)

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Router Components

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CPU

• The Central Processing Unit (CPU)

microprocessor

• Executes operating system instructions

System initialization

Routing functions

Network interface control

• Large routers may have multiple CPUs

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RAM• Dynamic RAM (DRAM)

Can be upgraded using Dual In-Line Memory Modules (DIIMS

• Stores

routing tables

Running configuration – temporarily while router is on

ARP cache

Performs packet buffering – packet queues

Maintains packet-hold queues

Run time space for executable Cisco IOS software

• Volatile – power fails information is lost

• Divided into

Main processor memory

Shared input/output (I/O) memory

Shared among interfaces for temporary storage of packets

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NVRAM

• Non-Volatile Random-Access Memory

• Provides storage for the startup/backup configuration file

• Non-volatile

Retains information when router is powered down or restarted

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Flash Memory

• Electronically erasable, programmable ROM (EEPROM)

• Holds full copy of operating system image (IOS)

Default settings for IOS is flash

Can be in compressed or uncompressed format

Executable copy of IOS transferred to RAM during boot up

Can store multiple versions of IOS

• IOS software can updated without removing and replacing chips on the processor

• Volatile

• To add or replace flash

Single In-Line Memory Modules (SIMMs)

PCMCIA cards can upgrade the amount of flash

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ROM

• Permanently stores startup diagnostic code

ROM Monitor

Hardware diagnositics - power-on self test (POST)

Stores bootstrap program

Loads CISCO IOS software from flash to RAM

• Not erasable

Can only be upgraded by replacing the ROM chips in the sockets of the motherboard

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Bus

• System Bus

Used to transfer packets between the CPU and the interfaces

• CPU Bus

Used by the CPU to transfers instructions and data to or from specified memory addresses

Power Supply

• Provides necessary power to operate the internal components

• Larger routers use multiple or modular power supplies

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Interfaces• Router connections to the outside

• Types of interfaces

LAN interfaces

Either ethernet or token ring connections

WAN interfaces

Serial, ISDN, and Integrated Channel Service Unit (CSUs

Console / Auxilary

Serial port used for initial configuration of the router

Used for terminal sessions from coms port on computer

• LAN and WAN configurations can be

Fixed – E1, E0, S1, S0

Modular – Fastethernet 0/0, Fastethernet 0/1, serial 0/1, serial 0/0

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Routers for Segmenting LAN

Routers operate at the network layer (3)They make decisions based on IP addressesDivide networks into smaller collision domainsDivide networks into smaller broadcast domains

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Routers have both LAN and WAN Connections

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• Making decisions based on network addresses

To determine the network address AND subnet mask and destination ip address

• Router functions

Routers select the best path

Routers switch the frames to the proper interface

• How do routers accomplish this

Building routing tables

Exchanging network information with other routers

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• Routing tables are maintained

Statically by administrator

Dynamically by routing protocols exchanging topology information

• A correctly configured internetwork provides

Consistent end-to-end addressing

Addresses that represent network topologies

Best path selection

Dynamic or static routing

Switching

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Routers Role in WAN

• WAN physical layer describes the interface between DTE and DCE

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Routers

• Operate as both LAN and WAN devices

• Can exclusively be a LAN or WAN device

LAN – L1, L2, L3

WAN – L1, L2

• Can sit at the boundary between a LAN and a WAN

LAN and WAN device at the same time

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• WAN physical layer standards and protocols:

EIA/TIA-232, EIA/TIA-449

V.24, V.35, X.21

G.703, EIA-530

ISDN, T1, T3, E1, and E3

xDSL, SONET (OC-3, OC-12, OC-48, OC-192)

• WAN data link layer standards and protocols:

High-level data link control (HDLC)

Frame Relay

Point-to-Point Protocol (PPP)

Synchronous Data Link Control (SDLC)

Serial Line Internet Protocol (SLIP)

X.25, ATM, LAPB, LAPD, LAPF Try the interactive media lab 1.1.5

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Internal Components of 2600 Router

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External Components of 2600 Router

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LAN interfaces Allow the router to connect to the Local Area Network mediaUsually some form of Ethernet (could be Token Ring)

Wide Area Network connectionsProvide connections through a service provider to a distant site

Management ConnectionsConsole Port or Auxiliary Port

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Configuration through Console Port

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• Used for

Initial router configuration

Monitoring

Disaster recovery procedures

(password recovery)

• Console port is preferred for troubleshooting

It displays router startup, debugging, error messages by default

Used when networking services have not been started/ failed

Console Port

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In order to configure a Router

• Terminal must support VT100 terminal emulation

HyperTerminal

• Configure terminal emulation software on the PC for:

The appropriate com port

9600 baud

8 data bits

No parity

1 stop bit

No flow control

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Modem Connection to Auxiliary Port

Used to configure router from a remote connection

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Connecting LAN Interfaces

• Ethernet Connection – E0, E1

• Fast Ethernet Connection – FastEthernet 0/0

Router communicates with LANVia a hub or switch

Crossover cable used to connect router Ethernet connection directly to a computer or another router

Straight Through Cable

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WAN Connection Types