Networks Fundamentals Based On Cisco Systems

Networks Fundamentals Based On Cisco Systems

Course Introduction

Cisco Career Certifications
CCNA Exam Expert Required Exam Recommended Training Through Cisco Learning Partners Lesson Aim <Enter lesson aim here.> CCIE CCNA Professional Cisco Certified Network Associate CCNP Introduction to Cisco Networking Technologies and Interconnecting Cisco Network Devices INTRO and ICND Associate CCNA

Course Topics - Day 1 : Introduction , OSI & TCP/IP Introduction
- Day 2 : OSI & TCP/IP Layers - Day 3 : IP Addressing - Day 4 : Introduction to Cisco IOS - Day 5 : Routing Fundamentals & WAN Overview

Networking Technologies
is basically all the components (H/W & S/W) involved in connecting computer across small and large distance Importance of Networks: Easy access and sharing of information Sharing of expensive devices and network resources Modern Technologies (IP telephony, Video on Demand, ….etc)

Network components Network has three main components
Computers (servers and hosts) - Source of applications (network aware applications) - ex: HTTP (Hyper Text Transmission Protocol), FTP (File Transfer Protocol), SNMP (Simple Network Management Protocol) Telnet Network Devices - Devices that interconnect different computers together - ex: Repeaters, hub, bridge, switch, router, NIC and modems Connectivity - Media that physically connect the computers and network devices - ex: Wireless and cables

Network Types LAN (Local Area Network):
It is a group of network components that work within small area MAN (Metropolitan Area Network): It is a group of LANs that are interconnected WAN (Wide Area Network): within large area

Reference Models - describe data transfer standards
- a framework (guideline) for network implementation and troubleshooting - divides complex functions in to simpler components - Reference model types : - OSI - TCP/IP

Reference Models The OSI Model The TCP/IP Model 7 Application
Transport Internet Network Access 6 Presentation 5 Session 4 Transport 3 Network 2 Data Link 1 Physical

OSI Model Overview Application (Upper) Layers Presentation Session
Transport Layer Layer 2 of 2: Purpose: This figure orients the students to the next set of concepts. Emphasize: The Data Link layer of the OSI reference model is implemented by Switches and Bridges. These devices encapsulate date in “frames”. The Network layer of the OSI reference model is implemented by Routers. These devices encapsulate data in ‘packets’. The Transport layer of the OSI reference model is implemented by various protocols; one of which is TCP. TCP uses ports and encapsulates the data in ‘segments’. Network Layer Data Flow Layers Data Link Physical

The OSI Reference model
transmission example A B 7 Application 7 Application 6 Presentation 6 Presentation 5 Session 5 Session 4 Transport 4 Transport 3 Network 3 Network 2 Data Link 2 Data Link 1 Physical 1 Physical

Encapsulation Process

Layer 7 - The Application Layer
This layer deals with networking applications. Examples:   Web browsers Each application uses a certain service from Transport Layer (reliable or unreliable) PDU - User Data 6 Presentation 5 Session 4 Transport 3 Network 2 Data Link 1 Physical

Layer 6 - The Presentation Layer
7 Application - Presenting the data in the required format which may include:  Encryption Compression - Translates between multiple data format by using a common format . PDU - Formatted Data 6 Presentation 5 Session 4 Transport 3 Network 2 Data Link 1 Physical

Layer 5 - The Session Layer
7 Application Establishes, manages, and terminates sessions between two communicating hosts. Example:  Client Software ( Used for logging in) PDU - Formatted Data 6 Presentation 5 Session 4 Transport 3 Network 2 Data Link 1 Physical

Layer 4 - The Transport Layer
7 Application -Breaks up the data from the sending host and then reassembles it in the receiver. (segmentation) -Insure reliable data transport across the network (reliability and flow control) PDU - Segments 6 Presentation 5 Session 4 Transport 3 Network 2 Data Link 1 Physical

Layer 3 - The Network Layer
7 Application Logical addressing (IP address) Selects the best Path Determination (routing) PDU - Packets 6 Presentation 5 Session 4 Transport 3 Network 2 Data Link 1 Physical

Layer 2 - The Data Link Layer
7 Application - provides reliable transit of data across a physical link hop by hop - Makes decisions based on physical addresses (usually MAC addresses) - Provides error detection PDU - Frames 6 Presentation 5 Session 4 Transport 3 Network 2 Data Link 1 Physical

Layer 1 - The Physical Layer
This is the physical media through which the data, represented as electronic signals, is sent from the source host to the destination host. Examples:  UTP  Coaxial (like cable TV)  Fiber optic PDU - Bits 7 Application 6 Presentation 5 Session 4 Transport 3 Network 2 Data Link 1 Physical

TCP/IP model The OSI Model The TCP/IP Model 7 Application Application
6 Presentation 5 Session 4 Transport 3 Network 2 Data Link 1 Physical Application Transport Internet Network Access

Hierarchical Network Model

The Physical Layer Purpose: This chapter introduces the Cisco IOS™ CLI on the Catalyst® 1900 switch and router. Timing: This chapter should take about 2 hours to present. Note: The Catalyst 1900 switch only has a subset of the router Cisco IOS commands available. Contents: Introduction to Cisco IOS. Explain to the student what is IOS? Cisco Device startup procedures in general. IOS configuration source. General introduction to the IOS CLI. Cat 1900 switch startup procedures. Intro to Cat 1900 CLI. This part covers the basic configuration on the switch, like setting the IP address and hostname. More details about the various Cat 1900 switch configuration commands are explained in Chapter 6 and 7. Router startup procedures. More details on the router startup process is discussed in chapter 5. Router IOS CLI. 23

Physical Layer Responsibilities
Description of LAN/WAN cables & connectors Description of LAN/WAN standards (maximum length, bit rates, pin assignment, voltage levels) Physical Layer Devices

LAN Physical Layer Ethernet cables : - Copper ( UTP , STP , Coaxial )
- Fiber

Unshielded Twisted Pair (UTP) Cable
prevents EMI , RFI CAT5 CAT 5e , CAT6 RJ-45 to avoid attenuation

Using UTP cable to connect devices
1- straight cable 2- cross cable 3- roll over cable

Straight-Through or Crossover cables
switch hub modem Cross cable PC router Cross cable straight cable

Shielded Twisted Pair (STP) Cable

Coaxial Cable thick coaxial , thin coaxial (200 m)

Fiber Optic Cable

Fiber Optic Connectors
single mode fiber multimode fiber

WAN Physical Layer serial cables

Transmission modes - Full duplex :
devices can send , receive data at the same time (two ways for transmission) - Half duplex: one circuit for transmission , so only one device can use the bus (send or receive) at a time , if two devices sent at the same time collision occurs .

Layer 1 devices 1- Repeater
A repeater is a network device used to regenerate a signal. Repeaters regenerate analog or digital signals distorted by transmission loss due to attenuation. Rule : no more than four repeaters can be used between hosts on a LAN.

repeater and hub work in half duplex mode
A Hub is a multi-port Repeater Hubs takes data bits from input port and forward it to all other ports repeater and hub work in half duplex mode

The Data-Link Layer Purpose: This chapter introduces the Cisco IOS™ CLI on the Catalyst® 1900 switch and router. Timing: This chapter should take about 2 hours to present. Note: The Catalyst 1900 switch only has a subset of the router Cisco IOS commands available. Contents: Introduction to Cisco IOS. Explain to the student what is IOS? Cisco Device startup procedures in general. IOS configuration source. General introduction to the IOS CLI. Cat 1900 switch startup procedures. Intro to Cat 1900 CLI. This part covers the basic configuration on the switch, like setting the IP address and hostname. More details about the various Cat 1900 switch configuration commands are explained in Chapter 6 and 7. Router startup procedures. More details on the router startup process is discussed in chapter 5. Router IOS CLI. 37

Data-Link Layer Responsibilities
Description of H/W addressing MAC (Media Access Control) address frame format Error detection between hop to hop Data-Link layer standards : LAN: Ethernet, Token Ring, FDDI WANs: HDLC, PPP, ISDN, X.25, Frame-Relay, ATM

Ethernet Overview - Ethernet is now the dominant LAN technology in the world. - Ethernet is not one technology but a family of LAN technologies. - Ethernet specifications support different media, bandwidths, and other Layer 1 and 2 variations.

MAC Address - MAC address is 48 bits in length and expressed as twelve
hexadecimal digits. - MAC addresses are burned into read-only memory (ROM) of the NIC - each NIC has a unique MAC address - MAC address can represent unicast , broadcast and multicast ex. A34C.52BD.1234

Ethernet Frame Structure

Layer 2 devices A layer 2 device is a device that understand MAC,
for example: NIC (Network Interface Card) Bridge : - address learning - forwarding decisions are based on software - bridge is used for LAN segmentation Switch: - a multi-port bridge - forwarding decisions are based on hardware ASIC (faster than bridge)

Ethernet Switches and Bridges
Emphasize: The next few slides discuss the basic function of a bridge/switch: 1. How it learns the location of the hosts by reading the source MAC address of incoming frames. 2. How it makes forwarding/filtering decisions. There are three conditions in which a switch will flood a frame out on all ports except to the port on which the frame came in, as follows: Unknown unicast address Broadcast frame Multicast frame 3. How STP is used to avoid loops in a switched/bridged network. Transparent Bridge and Switches has 3 main functions Address learning Forward/filter decision Loop avoidance

1- Address Learning Switch learns which MAC’s are connected to which ports by checking the frame source MAC address .

2- Forwarding - Forwarding is done by checking the destination MAC address - The frame is flooded if the destination MAC is unknown unicast or broadcast or multicast - for the known unicast, switch perform micro segmentation

Forwarding modes Cut-Through
Switch checks destination address and immediately begins forwarding frame. Fragment-Free Switch checks the first 64 bytes, then begins forwarding frame. Store and Forward Complete frame is received and checked before forwarding. Layer 3 of 3 Note: 64 bytes is the minimum Ethernet frame size. The command to switch the mode on the 1900 is: wg_sw_a(config)#switching-mode ? fragment-free Fragment Free mode store-and-forward Store-and-Forward mode

3- Remove Layer 2 loops MAC port A 3 1
Lesson Aim <Enter lesson aim here.> MAC port A 3 1 Solution : using Spanning tree protocol (STP)

Frame creation Burned on the NIC - ARP - Proxy ARP - Static
Source MAC Destination MAC Source IP Destination IP Burned on the NIC - ARP - Proxy ARP - Static - Dynamic (RARP , BOOTP , DHCP) DNS

- Source MAC Burned on the NIC

- Source IP 1- by static configuration

- Source IP - DHCP : - Dynamic host configuration protocol
- DHCP allows a host to obtain an IP address dynamically without the network administrator having to set up an individual profile for each device. - a range of IP addresses on a DHCP server is defined . - the entire network configuration of a computer can be obtained in one message from the server. Lesson Aim <Enter lesson aim here.>

- Destination IP DNS : Application specified in the TCP/IP suite
Means to translate human-readable names into IP addresses

- Destination MAC - ARP :
- each PC form an ARP table containing the learned MAC’s Lesson Aim <Enter lesson aim here.>

- Destination MAC - Proxy ARP : A B Router R I take care, to forward
Broadcast Message to all: If your IP address matches “B” then please tell me your Ethernet address B Yes, I know the destination network, let me give you my I take care, to forward IP packets to B - Proxy ARP :

The Transport Layer Purpose: This chapter introduces the Cisco IOS™ CLI on the Catalyst® 1900 switch and router. Timing: This chapter should take about 2 hours to present. Note: The Catalyst 1900 switch only has a subset of the router Cisco IOS commands available. Contents: Introduction to Cisco IOS. Explain to the student what is IOS? Cisco Device startup procedures in general. IOS configuration source. General introduction to the IOS CLI. Cat 1900 switch startup procedures. Intro to Cat 1900 CLI. This part covers the basic configuration on the switch, like setting the IP address and hostname. More details about the various Cat 1900 switch configuration commands are explained in Chapter 6 and 7. Router startup procedures. More details on the router startup process is discussed in chapter 5. Router IOS CLI. 55

The Transport Layer reliable service unreliable service

Flow Control - Windowing (PAR): error in 2 2 2 2 3 3 Lesson Aim
<Enter lesson aim here.> error in 2 2 2 2 3 3

Flow Control - Windowing (PAR):

Multiplexing applications
2 1 web server 3 Source IP Destination IP Source port Destination port 1 1200 80 2 1500 80 3 1200 80

TCP Header Lesson Aim <Enter lesson aim here.>

UDP Header Lesson Aim <Enter lesson aim here.>

The Application Layer Purpose: This chapter introduces the Cisco IOS™ CLI on the Catalyst® 1900 switch and router. Timing: This chapter should take about 2 hours to present. Note: The Catalyst 1900 switch only has a subset of the router Cisco IOS commands available. Contents: Introduction to Cisco IOS. Explain to the student what is IOS? Cisco Device startup procedures in general. IOS configuration source. General introduction to the IOS CLI. Cat 1900 switch startup procedures. Intro to Cat 1900 CLI. This part covers the basic configuration on the switch, like setting the IP address and hostname. More details about the various Cat 1900 switch configuration commands are explained in Chapter 6 and 7. Router startup procedures. More details on the router startup process is discussed in chapter 5. Router IOS CLI. 62

TCP/IP Application Layer Overview
File transfer FTP TFTP Simple Mail Transfer Protocol Remote login Telnet Network management Simple Network Management Protocol Name management Domain Name System Purpose: This figure discusses application-layer protocols. Emphasize: The common network applications today include file transfer, remote login, network management, and . We focus on TCP/IP in this course for several reasons: TCP/IP is a universally available protocol and you will use it at work. TCP/IP is a useful reference for understanding other protocols, because it includes elements that are representative of other protocols. TCP/IP is important because the router uses it as a configuration tool. The router uses Telnet for remote configuration, TFTP to transfer configuration files and operating system images, and SNMP for network management. Transition: The next section moves down the model to discuss the transport layer.

Port Numbers Lesson Aim <Enter lesson aim here.>

The TCP/IP Internet Layer
Purpose: This chapter introduces the Cisco IOS™ CLI on the Catalyst® 1900 switch and router. Timing: This chapter should take about 2 hours to present. Note: The Catalyst 1900 switch only has a subset of the router Cisco IOS commands available. Contents: Introduction to Cisco IOS. Explain to the student what is IOS? Cisco Device startup procedures in general. IOS configuration source. General introduction to the IOS CLI. Cat 1900 switch startup procedures. Intro to Cat 1900 CLI. This part covers the basic configuration on the switch, like setting the IP address and hostname. More details about the various Cat 1900 switch configuration commands are explained in Chapter 6 and 7. Router startup procedures. More details on the router startup process is discussed in chapter 5. Router IOS CLI. 65

Internet Layer Internet Layer is responsible for the following:
Support of logical addressing for network components Routing (Finding the best path for data) Layer 3 devices Internet Layer protocols are IP (Internet Protocol) ICMP (Internet Control Management Protocol) ARP (Address Resolution Protocol), RARP (Revere ARP) Routing Protocols ex. OSPF , EIGRP ,

IP (Internet Protocol)
IP has the following characteristics Provide Logical addressing Provide connectionless “best effort” delivery of data

IP Packet IP packets consist of the data from upper layers plus an IP header. The IP header consists of the following:

IP addressing - Each host in the network must have a unique IP address
because duplicate addresses would make routing impossible - IP Addressing is a hierarchical structure as the IP address combines two identifiers into one number . the first part identifies the network address , the second part, called the host part, identifies which particular machine it is on the network. - IP address is a 32 bit (4 bytes= 4 octets) address that is mainly divided to network part (representing the network ID where the device is located in) & Host part (representing the ID of the host) - It is represented in a dotted decimal form, where each octet is transformed to its decimal value. ex

IP Address Classes IP addresses are divided into classes to define the large, medium, and small networks. Class A addresses are assigned to larger networks. Class B addresses are used for medium-sized networks, Class C for small networks, Class D for Multicasting Class E for Experimental purposes

Identifying Address Classes
Note : for Class A , networks 0 & 127 are reserved (class A range )

Public IP Addresses - Unique addresses are required for each device on a network - Originally, an organization known as the Internet Assigned Numbers Authority (IANA) handled this procedure. - No two machines that connect to a public network can have the same IP address because public IP addresses are global and standardized.

Private IP Addresses Private IP addresses are another solution to the problem of the impending exhaustion of public IP addresses.As mentioned, public networks require hosts to have unique IP addresses. However, private networks that are not connected to the Internet may use any host addresses, as long as each host within the private network is unique.

IP address types IP address could be one of three categories
Network address Host address Broadcast address

Network / Broadcast Addresses
- Network address : the first IP address in it which all host part bits = 0 - Broadcast address: the last IP address in the network which all host part bits = 1 no. of host bits - other addresses are host addresses = - Here are some examples: Class Network Address Broadcast Address A B C

Subnet Mask - 32 bit mask ( 1’s followed by 0’s )
- Used by routers and hosts to determine the number of network- significant bits ( identified by 1’s ) and host- significant bits in an IP address (identified by 0’s) - example : Class Network Address Default subnet mask A or /8 B or /16 C or /24

Octet Values of a Subnet Mask
Subnet masks like IP addresses can be represented in the dotted decimal format like

Subnetting Network part Host part Network part Host part
- Subnetting a network means to use the subnet mask to divide the network and break a large network up into smaller, more efficient and manageable segments, or subnets. - Subnetting is done by taking part of host bits then add it to the network part IP address Network part Host part Subnet bits Network part Host part

Subnetting Example Divide network 192.168.1.0/24 into 4 subnets
Solution: 4 subnets need 2 bits to to to to subnet mask is or /26 The first subnet is /26 The second subnet is /26 The third subnet is /26 The fourth subnet is /26 0 - 63

Divide network 192.168.1.0/24 into 4 subnets
Solution : - 4 subnets need 2 bits - subnet mask = - interesting octet is 192 - hop count = 256 – 192 = 64 - The first subnet is /26 - The second subnet is /26 - The third subnet is /26 - The fourth subnet is /26

Determine if this IP is network address or host address or broadcast address 172.16.5.0/23
Solution : - subnet mask = - interesting octet is 254 - hop count = 256 – 254 = 2 - The first subnet is /23 - The second subnet is /23 - The third subnet is /23 - The fourth subnet is /23 So /23 is a host address /23

- Which IP address should be assigned to PC B ?
/27 ? Answer : C

- Given the choices below, which address represents a unicast address?
B . FFFF. FFFF. FFFF. C /30 D E /18 Answer : E

Layer 3 devices Router : - Best path determination
- Creating routing table - Connecting different LANs - Network traffic filtration - Quality Of Serves .

Find number of broadcast domains and number of collision domains
Solution : no. of broadcast domains = 2 no. of collision domains = 4

Operating Cisco IOS Software
Purpose: This chapter introduces the Cisco IOS™ CLI on the Catalyst® 1900 switch and router. Timing: This chapter should take about 2 hours to present. Note: The Catalyst 1900 switch only has a subset of the router Cisco IOS commands available. Contents: Introduction to Cisco IOS. Explain to the student what is IOS? Cisco Device startup procedures in general. IOS configuration source. General introduction to the IOS CLI. Cat 1900 switch startup procedures. Intro to Cat 1900 CLI. This part covers the basic configuration on the switch, like setting the IP address and hostname. More details about the various Cat 1900 switch configuration commands are explained in Chapter 6 and 7. Router startup procedures. More details on the router startup process is discussed in chapter 5. Router IOS CLI. 87

Cisco Software components
Cisco IOS (Internetwork Operating System) It is the operating system that manages the hardware platform it is working on. Configuration File It is a program file that contains commands that reflect how the router will react.

Router Internal Components
Note: RAM—Packet buffers, running configurations, running Cisco IOS ROM—POST, ROM monitor, baby Cisco IOS (Rxboot) NVRAM—Backup configurations, config register Flash—Cisco IOS Flash memory is nonvolatile. It behaves like a file system. It is more expensive than NVRAM. It is readable and writeable. The 2500 routers run from Flash. If it is running Cisco IOS from Flash, then the Flash is in the readable state. Use the boot system command to boot Cisco IOS from a TFTP server so the 2500 can run from RAM if you need to write or erase Flash online.

An Overview of Cisco Device Startup
Purpose: This slide introduces the startup process on Cisco routers and switches. Emphasize: Paraphrase or restate the three points and make sure your students follow the description. This description is necessary to keep a common perspective of what is occurring on the switch and the router; these three steps should be an anchor to return to as needed. Transition: Where are the sources for configuration software?

Step in Router Initialization

External Components of a 2600 Router

Computer/Terminal Console Connection

HyperTerminal Session Properties

Setup mode - Permit the administrator to install a minimal configuration for a router ( appeared if no saved configuration , Ctrl-C to skip ) Purpose: This slide describes the console output on the Catalyst 1900 switch during startup. Emphasize: If a POST fails, a corresponding console message will be displayed indicating the POST failure. In this slide, the switch started up without any POST error. From the User Interface menu, select K to access the command-line interface. In this class, we will only discuss the Catalyst 1900 CLI configuration method.

Other Router Modes Emphasize: Here is a list of some of the configuration modes available. For a complete list of the router configuration modes, refer to the Cisco Documentation CD-ROM.

IOS Features Support context help and abbreviations ( ? )
Support of auto complete ( Tab button ) Support syntax error detection

Context help features

Configuring Router Identification
Slide 2 of 2 Emphasize: Layer 2—The interface description command allows you to enter a one-line descriptive statement for each interface. This description is displayed in the output from the show interfaces command and appears in the show running-config and show startup-config listings.

Configuring a Router Password
Layer 2 of 2 Emphasize: The router has one enable password. Remember that this is your only protection. Whoever owns this password can do anything with the router, so be careful about communicating this password to others. To provide an additional layer of security, particularly for passwords that cross the network or are stored on a TFTP server, you can use either the enable password or enable secret commands. Both commands accomplish the same thing; that is, they allow you to establish an encrypted password that users must enter to access enable mode (the default), or any privilege level you specify. Cisco recommends that you use the enable secret command because it uses an improved encryption algorithm. Use the enable password command only if you boot an older image of the Cisco IOS software, or if you boot older boot ROMs that do not recognize the enable secret command. If you configure the enable secret password, it is used instead of the enable password, not in addition to it. Cisco supports password encryption. Turn on password encryption using the service password-encryption command. Then enter the desired passwords for encryption. Immediately, on the next line, enter the no service password-encryption command. Only those passwords that are set between the two commands will be encrypted. If you enter service password-encryption and then press Ctrl-Z to exit, all passwords will be encrypted. Note: Password recovery is not covered in the course materials. Refer the students to the IMCR class.

Configuring Interfaces
/30 /30 Router#config t RouterA(config)# interface serial 0/0 RouterA(config-if)# ip address RouterA(config-if)# no shutdown RouterA(config-if)# clock rate (required for serial DCE only) RouterA(config-if)# bandwidth (a value in kbps) RouterA(config-if)# exit RouterB(config)# int serial 0/ RouterB(config-if)# ip address RouterB(config-if)# no shutdown RouterB(config-if)# exit RouterB(config)# exit Router# To know which interface is the DCE : RouterA# show controller s0/0

monitoring and debugging
show commands are typed in both privileged EXEC and user EXEC modes #show interfaces – Displays all the statistics for all the interfaces #show int s0/ – Displays statistics for interface Serial 0/1 #show ip interface brief – Displays a summary about interfaces #show flash – Displays info about flash memory and what IOS in it #show start – Displays the saved configuration located in NVRAM #show run – Displays the configuration currently running in RAM #show version – Displays info about the router and the IOS #show ARP – Displays the ARP table of the router #show protocol – Displays the global and interface specific status of any configured Layer 3 protocols #show controllers serial0/ – Displays information-specific to the interface hardware #erase nvram – erase the saved configuration file #reload – restart the router #copy run start – save the current configuration in RAM into the NVRAM

show version Command Purpose: This slide presents the show version command. Emphasize: Point out that this command is useful when troubleshooting problems because it gives the versions of the various software components and files. It also displays how long the router has been in operation and where it obtained the image file. Config register is discussed in Chapter 6, “Catalyst Switch Operations.”

Configuration Register Values
The configuration register value set the boot option Layer 4 of 4 Emphasize: Layer 4—Finishes with the third case, a boot field setting in the range of 0x2 to 0xF. The entry of a configuration register value in the 0x2 to 0xF range is significant. When the router attempts to boot from the net (Netboot), the bootstrap program generates a Cisco IOS filename based on the value of the boot field. For example, with the setting 0x2, the default Cisco IOS filename generated will be cisco2-xxxx, where xxxx refers to a processor name (for example, 2500). Again, refer students to the IMCR course for details. You use the config-register command to change the value. Notice that the bottom lines of the show version output indicates what value the config register will be on the next reload. 0x2100 0x2101 0x2102 to 0x210F The value 0x2142 is used to bypass the NVRAM

Boot system command - beside the configuration register you can use the boot system command to force booting location. Router(config)# boot system flash Router(config)# boot system rom Router(config)# boot system tftp

show flash command Emphasize: The show flash command is an important tool to use to gather information about your router memory and image file. Caution students that they must know that they are loading the correct and appropriate image. The name for the Cisco IOS image file contains multiple parts, each with a specific meaning: The first part of the image name contains the platform on which the image runs. In this example, the platform is C2500. The second part of the name identifies the special capabilities of the image file. A letter or series of letters identifies the feature sets supported in that image. In this example, the “j” indicates this is an enterprise image, and the “s” indicates it contains extended capabilities. The third part of the name specifies where the image runs and if the file is compressed. In this example, “l” indicates the file is relocatable and not compressed. Relocatable means the Cisco IOS can be run from Flash or from RAM. You should be careful in reading the Cisco IOS image filename. Some fonts display the lowercase letter “l” and the number 1 as the same character. How you enter the characters will impact the ability of the router to load the files correctly. The fourth part of the name indicates the version number. In this example, the version number is 12.0 (3). The final part of the name is the file extension. The .bin extension indicates this file is a binary executable file. The Cisco IOS software naming conventions, name part field meaning, image content, and other details are subject to change. Refer to Cisco Connection Online (CCO) for updated details.

show running-config and show startup-config Commands
Purpose: This slide is a repeated slide from Chapter 4, “Operating and Configuring a Cisco IOS Device.” Displays the current and saved configuration

show interfaces Command
Purpose: This slide presents the show interfaces command, which indicates whether the network is operating at the physical and data link layers. The command output is interpreted later in this chapter. Emphasize: The top line of the output tells us that the line is up. A few lines down, the output provides the IP address, and below that some characteristics like BW for bandwidth, and DLY for delay. On the next line down, we find an encapsulation type of ARPA. ARPA means Ethernet II, which is the default IP encapsulation type for Ethernet interfaces on Cisco routers. A runt is an Ethernet frame that is too small to be legal (less than 64 bytes), and a giant is an Ethernet frame that is too big (greater than 1518 bytes).

Interpreting the Interface Status
Interface is working properly Layer 1 status Layer 2 status Other interface status : Purpose: This slide explains how to interpret the show interfaces serial command output. Emphasize: The show interfaces serial command output indicates that the serial interface is up and the line protocol is up. The first parameter refers to the hardware layer and essentially reflects whether the interface is receiving the Carrier Detect signal from the other end. The second parameter refers to the data link layer. This parameter reflects whether the data link layer protocol keepalives are being received. If both the interface and the line protocol are up, the connection is operational. If the hardware is up and the line protocol is down, a connection problem exist such as no clocking, wrong encapsulation type, or no keepalives. If both the line protocol and the interface are down, a cable might never have been attached to the router. On the serial cable, you can plug in the cable upside-down, causing the pins on the serial cable to break. There is one more possibility. If the information says “administratively down,” you have manually disabled (shut) the interface. Cisco offers a hardware class (IMCR) that discusses the router hardware in more detail. - Serial0/1 is administratively down , line protocol is down interface is shut down - Serial0/1 is down , line protocol is down interface or cable H/W failure ( no keep-alives ) - Serial0/1 is up , line protocol is down different encapsulation type ( PPP , HDLC , FR ) or no clock rate on the DCE device.

Serial Interface show controller Command
Emphasize: This command requires a space between the word serial and the interface number. The router only checks for the cable type at powerup. Shows the cable type of serial cables

Discovering Neighbors with CDP
CDP runs on routers with Cisco IOS to get information about the direct connected Cisco devices. Summary information includes: Device identifiers Address list Port identifier Capabilities list Platform Emphasize: CDP is media- and protocol-independent and runs on all Cisco-manufactured equipment including routers, access servers, switches, and some managed hubs. With CDP, network management applications can retrieve the device type and SNMP agent address of neighboring devices. This capability enables applications to send SNMP queries to neighboring devices. CDP allows network management applications to dynamically discover Cisco devices that are neighbors. CDP runs on all media that support the Subnetwork Access Protocol, including LAN and Frame Relay. CDP runs over the data link layer only, not the network layer. Therefore, two systems that support different network-layer protocols can learn about each other. Cached CDP information is available to network management applications. Cisco devices never forward a CDP packet. When new information is received, old information is discarded. The holdtime determines how long to keep existing information from a neighbor.

Using the show cdp neighbors Command
Emphasize: This graphic shows the show cdp neighbors command initiated from a router, which displays a summary of the capabilities and access details for the CDP neighbors. The show cdp neighbors detail command shows detailed information about the same devices. Note: If the neighbor is a Catalyst 1900 switch, the switch MAC address is also displayed. If the switch is a 2900xl, its MAC address is not displayed. RouterA# show cdp neighbors detail provide also the neighbors ip addresses.

Using Telnet to Connect to Remote Devices
Emphasize: Another way to learn about a remote device is to connect to it. Telnet, a virtual terminal protocol that is part of the TCP/IP protocol suite, allows connections to remote hosts. By default, a router can have up to five simultaneous incoming Telnet sessions. With Cisco’s implementation of TCP/IP, you need not enter the connect or telnet command to establish a Telnet connection. If you prefer, you can just enter the learned host name, and the router will resolve the host name using DNS or a local host table. To end a Telnet session, use the exit or logout EXEC command. These are alternate commands for the operations listed on the graphic: Initiate a session: Denver> connect paris Denver> paris Denver> Resume a session (enter session number or name): Denver> 1 Paris> End a session: Paris> exit Note: The Catalyst 1900 can accept incoming Telnet connections but cannot initiate an outgoing Telnet session. Telnet is used to check all the TCP/IP stack

Using the ping and trace Commands
Emphasize: As you use CDP and Telnet, you should note the information retrieved from the devices you successfully contacted. Documenting that information helps put the network into a visual perspective, and can be referenced at a later time. This concludes the network discovery portion of the chapter. In the next section, we will discuss configuration file and Cisco IOS image management. Ping commands tests the connectivity and path to a remote device ( test layer 3 in TCP/IP )

Cisco IOS copy Command To save IOS image or configuration file # # # #
Layer 4 of 4 # # # #

Networks Fundamentals Based On Cisco Systems

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Networks Fundamentals Based On Cisco Systems

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