Bài giảng mạng máy tính nâng cao (advanced computer networks) chương 2 wan and router

 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 comm

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Mạng Máy Tính Nâng Cao

Chương 2:WAN AND ROUTER

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 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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 Describe the purpose of the IOS

 Describe the basic operation of the IOS

 Identify various IOS features

 Identify the methods to establish a command-line interface (CLI) session with the router

 Move between the user command executive (user EXEC) and privileged EXEC modes

 Establish a HyperTerminal session on a router

 Log into a router

 Use the help feature in the command line interface

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 Communication servers concentrate dial-in and dial-out user communication

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 WAN physical layer protocols describe how to

provide electrical, mechanical, operational, and functional connections for WAN services

 WAN data link protocols describe how frames are

carried between systems on a single data link

 WAN standards are defined and managed by a

number of recognized authorities, including the following agencies:

 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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WAN physical layer protocols

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WAN data link protocols

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 High-Level Data Link Control (HDLC) an IEEE standard; 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, which means it can send Layer 2 information much more rapidly than other WAN protocols

 Point-to-Point Protocol (PPP) described by RFC

1661; two standards developed by the IETF; contains

a protocol field to identify the network layer protocol

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 Link Access Procedure Balanced (LAPB) data

link protocol used by X.25; has extensive error checking capabilities

 Link Access Procedure D-channel (LAPD) the

WAN data link protocol used for signaling and call setup on an ISDN D-channel Data transmissions take place on the ISDN B channels

 Link Access Procedure Frame (LAPF)

for Frame-Mode Bearer Services; a WAN data link protocol, similar to LAPD, used with frame relay technologies

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 POTS (Plain Old Telephone Service) not a computer

data service, but included for two reasons: (1) many of its technologies are part of the growing data infrastructure, (2) it is a model of an incredibly reliable, easy-to-use, wide-area communications network; typical medium is twisted-pair copper wire

 Narrowband ISDN (Integrated Services Digital Network) a versatile, widespread, historically important

technology; was the first all-digital dial-up service; usage varies greatly from country to country; cost is moderate;

maximum bandwidth is 128 kbps for the lower cost BRI (Basic Rate Interface) and about 3 Mbps for the PRI

(Primary Rate Interface); usage is fairly widespread, though it varies considerably from country to country; typical medium is twisted-pair copper wire

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 X.25 an older technology, but still widely used; has

extensive error-checking capabilities from the days when WAN links were more prone to errors, which make it reliable but limits its bandwidth; bandwidth may be as high as 2 Mbps;

 Frame Relay a packet-switched version of

Narrowband ISDN; has become an extremely popular WAN technology in its own right; more efficient than X.25, but with similar services; maximum bandwidth is 44.736 Mbps; 56kbps and 384kbps are extremely popular in the U.S.; usage is widespread; cost is moderate to low; Typical media include twisted-pair copper wire and optical fiber

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 ATM (Asynchronous Transfer Mode) closely

related to broadband ISDN; becoming an increasingly important WAN (and even LAN) technology; uses small, fixed length (53 byte) frames to carry data; maximum bandwidth is currently 622 Mbps, though higher speeds are being developed; typical media are twisted-pair copper wire and optical fiber; usage is widespread and increasing; cost is high

 SMDS (Switched Multimegabit Data Service)

closely related to ATM, and typically used in MANs; maximum bandwidth is 44.736 Mbps; typical media are twisted-pair copper wire and optical fiber; usage not very widespread; cost is relatively high

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Dedicated Digital Services

 T1, T3, E1, E3 the T series of services in the U.S and the

E series of services in Europe are extremely important WAN technologies

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Dedicated Digital Services

 SONET (Synchronous Optical Network) a family of very high-speed physical layer technologies; designed for optical fiber, but can also run on copper cables implemented at different OC (optical carrier) levels ranging from

51.84 Mbps (OC-1) to 9,952 Mbps (OC-192)

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 Dial-up modems (switched analog)

 Cable modems (shared analog)

 Wireless

WAN Technology-CompleteView

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Routers are Computers

 Routers are at the network center

• A router connects multiple networks This means

that it has multiple interfaces that each belong to a different IP network

• Each network that a router connects to typically

requires a separate interface These interfaces are used to connect a combination of both Local Area Networks (LANs) and Wide Area Networks (WANs).

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Routers are Computers

primary responsibility of a router is to direct packets destined for local and remote networks by:

• Determining the best path to send packets

• Forwarding packets toward their destination

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 Integrated voice and data capabilities, allowing routers

to provide voice gateway features for IP telephony.

 Today the router is an integrated platform for providing advanced services in security, content delivery, and

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Cisco Router Series

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Router Internal Components

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 CPU-Executes operating system instructions

 Random access memory (RAM)-Contains the running copy of configuration file Stores routing table RAM contents lost when power is off

 Read-only memory (ROM)-Holds diagnostic software used when router is powered up Stores the router’s bootstrap program

 Non-volatile RAM (NVRAM)-Stores startup configuration This may include IP addresses (Routing protocol, Hostname of router)

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 Flash memory -Contains the operating system (Cisco IOS)

 Interfaces -There exist multiple physical interfaces that are used to connect network Examples of interface types:

• Ethernet / FastEthernet interfaces

• Serial interfaces

• Management interfaces

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 Interfaces – The router connections to the outside The three types of interfaces:

• Local-area network (LANs),

• Wide-area network (WANs),

• Console/AUX

 The LAN interfaces are usually one of several different varieties of Ethernet or Token Ring The LAN interfaces may be a fixed configuration or modular

 The WAN interfaces include serial, ISDN The WAN interfaces may be a fixed configuration or modular

 The Console/AUX ports are serial ports used primarily for the initial configuration of the router They are used for terminal sessions from the communication ports on the computer or through a modem

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 Router Interface is a physical connector that enables

a router to send or receive packets

 Each interface connects to a separate network

 Consist of socket or jack found on the outside of a router

 Types of router interfaces:

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• Are used to connect

router to LAN network

• Has a layer 2 MAC address

• Can be assigned a Layer

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Routers and the Network Layer

 The main purpose of a router is to connect multiple networks and forward packets destined either for its own networks or other networks

 A router is considered a Layer 3 device because its primary forwarding decision is based on the information in the Layer 3 IP packet, specifically the destination IP address This process is known

as routing

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Routers and the Network Layer

 Routers Operate at Layers 1, 2 & 3

• Router receives a stream of encoded bits

• Bits are decoded and passed to layer 2

• Router de-encapsulates the frame

• Remaining packet passed up to layer 3

 Routing decision made at this layer by examining destination IP address

• Packet is then re-encapsulated & sent out

outbound interface

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Connecting console interfaces

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 To connect the PC to a router : Configure

terminal emulation software (HyperTerminal) on the PC for:

• The appropriate com port

 Connect the RJ-45 connector of the rollover cable

to the router console port

 Connect the other end of the rollover cable to the

RJ-45 to DB-9 adapter

 Attach the female DB-9 adapter to a PC

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Connecting auxiliary (AUX) port

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Connecting WAN interfaces

Show more

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• Basic routing and switching functions

• Reliable and secure access to networked resources

 The IOS file: several megabytes, is stored in a semi-permanent

memory area called flash Flash memory provides non-volatile storage.

 Using flash memory allows the IOS to be upgraded to newer versions or to have new features added The IOS may be copied into RAM when the device is powered on and the IOS runs from RAM when the device is operating.

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• Low speed serial connection to directly connect a

computer or terminal to the console port on the router or switch

• Provides access to a router

• Often used to access a device when the networking

services have not been started or have failed.

 Examples of console use are:

• The initial configuration of the network device

• Disaster recovery procedures and troubleshooting

where remote access is not possible

• Password recovery procedures

• The device should be located in a locked room or

equipment rack to prevent physical access.

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• Require active networking services on the device.

• Run on layer 7 in OSI model

 Secure Shell (SSH) protocol

• Like telnet but more secure access

• Stronger password

• Uses encryption when transporting session data

• Use can use ssh client on PC name: Putty

http://www.chiark.greenend.org.uk/~sgtatham/putt y/download.html

 As a best practice, always use SSH in place of Telnet whenever possible.

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 Another way to establish a CLI session remotely

is via a telephone dialup connection using a

modem connected to the router's AUX port

 Can used locally, like console port

 Console port is also preferred over the auxiliary port for troubleshooting because it displays router startup, debugging, and error messages

by default

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Establishing a HyperTerminal session

 Take the following steps to connect a terminal

to the console port on the router:

1 Connect the terminal using the RJ-45 to RJ-45

rollover cable and an RJ-45 to DB-9 or RJ-45 to DB-25 adapter

2 Configure the terminal or PC terminal emulation

software for 9600 baud, 8 data bits, no parity, 1 stop bit, and no flow control

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Types of Configuration Files

• used during the current operation of the

device

• Changes to the running configuration will

immediately affect the operation of the Cisco device

• used as the backup configuration and is

loaded when the device is started

• The startup configuration file or startup-config

file is stored in non-volatile RAM (NVRAM)

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Router user interface modes

 For security purposes, the router has

two levels of access to commands

• User EXEC mode Typical tasks include

those that check the router status In this mode, router configuration changes are not allowed

• Privileged EXEC mode Typical tasks

include those that change the router configuration

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Router user interface modes

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Cisco IOS Modes

 Different modes and the mode prompts in the CLI

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Basic IOS Command Structure

 After entering each complete command, including

any keywords and arguments, press the <Enter>

key to submit the command to the command interpreter

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Using CLI Help

 Using “?”

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Using CLI Help

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Using CLI Help

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Using CLI Help

 Tab -Completes the remainder of the command or

 Ctrl-Shift-6-Allows the user to interrupt an IOS

process such as ping or traceroute

 Ctrl-C orCtrl-Z -Aborts the current command and

exits the configuration mode

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Enhanced editing commands

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Router command history

 Set the command history buffer size

 Recall commands

 Disable the command history feature

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IOS Configuration modes

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IOS Configuration mode

 Interface mode-to configure one of the network

interfaces (Fa0/0, S0/0/0, )

 Line mode-to configure one of the lines (physical or

virtual) (console, AUX, VTY, )

 Router mode-to configure the parameters for one of

the routing protocols

 Remember, as configuration changes are made within an interface or process, the changes only affect that interface or process.

• Once a change has been made from the global

mode, it is good practice to save it to the startup configuration file stored in NVRAM

Router#copy running-config startup-config

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Global Configuration Mode

 All command-line interface (CLI) configuration changes

to a Cisco router are made from the global configuration mode For Examples:

• exit : Returns the router to global configuration mode from one of these specific configuration modes

• Ctrl-Z : Returns the router to privileged EXEC mode

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