BASIC NETWORKING LAB MANUAL FOR BEGINNERS
Version 1.0CONTENTS :
1. Introduction
2. Numbering Systems and Conversion
a. Binary numbers to decimal numbers conversion and vice versa
b. Binary to Hexadecimal conversion and vice versa
c. Decimal to Hexadecimal conversion and vice versa
3. IPv4 Addressing
4. Subnetting
5. DHCP (Dynamic Host Configuration Protocol)
a. Common DHCP configuration parameters
b. Configuring TCP/IP Configuration Settings Manually Without a DHCP Server
6. DOS Utilities for Troubleshooting Network problems
a. PING b. TRACERT c. IPCONFIG d. IPCONFIG/ALL e. NBTSTAT f. NETSTAT g. NETSH
7. Frequently used TCP/IP Protocols
a. HTTP
b. FTP
c. Telnet
d. Email-Protocols (SMTP, POP, and IMAP)
8. Connectors and Cabling
a. DB9
b. DB25
d. RJ-11
e. RJ-45
f. DB9 to USB
9. Appendix
a. Troubleshooting Network Interface Card (NIC) For Physical Connectivity
b. Modem connectivity and Troubleshooting
1. Introduction:
This manual provides information that was previously assumed that a candidate will have prior to working with Juniper router networks. The manual covers topics such as number conversion, networking connectors and cables, and troubleshooting network connectivity.
2. Numbering Systems and Conversion:
We need to convert from one system to another during the process of network design and implementation. For example, when you are optimizing for subnet mask or designing a wildcard mask (you will learn it while studying for Cisco Certification exams) you need to convert one numbering system to another. Of course, there are calculators available for this purpose. Three important systems of numbering are:
a. Decimal - The Decimal system is what you use everyday when you count. The system uses ten digits: 0, 1, 2, 3, 4, 5, 6, 7, 8 and 9. These digits are what we call the symbols of the decimal system.
b. Binary - The Binary system uses two symbols, 0 and 1. Basically, a computer uses binary digits for all its operations and understands only binary values. Each symbol is
represented by low level or high level signal.
c. Hexadecimal - This system uses 16 symbols, these are 0 - 9, A, B, C, D, E, F. The need for Hex system aroused because the Hex numbers can easily broken in to binary digits for consumption by digital computers and vice versa. For example, a large binary number such as 1101 1011 1110 1001 is equivalent to B7D2 H (H or h is used for hexadecimal system). Another advantage of hex system is that it is easy to be understood by humans. The following sections explain conversion from one numbering system to another.
a. Binary Numbers to Decimal Number Conversion and Vice Versa:
Decimal is a Base 10 system with 10 possible values (0 to 9) and Binary is a Base 2 system with only two numbers 0 or 1.
i. Converting binary to decimal - The weightage of binary digits from right most bit position to the left most bit position is given below.
27 26 25 24 23 22 21 20
128 64 32 16 8 4 2 1
There are eight bits in the binary number. The decimal value for each bit position is given below:
128 64 32 16 8 4 2 1 « Decimal equivalent of the binary position 1 0 0 1 1 1 0 1 « Given binary number
To convert, you simply take a value from the top row wherever there is a 1 below, and then add the values together.
For instance, in our example we would have
1*27 + 0*26 + 0*25 + 1*24 + 1*23 + 1*22 + 0*21 + 1*20 =128 + 0 + 0 + 16 + 8 + 4 + 0 + 1 = 157 (decimal value)
ii. Converting decimal to binary
To convert decimal to binary is also very simple, you simply divide the decimal value by 2 and then write down the remainder, repeat this process until you cannot divide by 2 anymore.
For example, take the decimal value 157: 157 ÷ 2 = 78 with a remainder of 1 78 ÷ 2 = 39 with a remainder of 0 39 ÷ 2 = 19 with a remainder of 1 19 ÷ 2 = 9 with a remainder of 1 9 ÷ 2 = 4 with a remainder of 1 4 ÷ 2 = 2 with a remainder of 0 2 ÷ 2 = 1 with a remainder of 0
1 ÷ 2 = 0 with a remainder of 1 <--- to convert, write this remainder first Next write down the value of the remainders from bottom to top (in other words write down the bottom remainder first and work your way up the list) which gives:
10011101 = 157
b. Binary to Hexadecimal Conversion and Vice Versa:
To convert binary to hexadecimal, take blocks of 4 bits of the binary number starting from the right most bit and convert it to equivalent hexadecimal number using the following table:
Hex digit Equivalent binary value
0 0000 1 0001 2 0010 3 0011 4 0100 5 0101 6 0110 7 0111 8 1000 9 1001 A 1010 B 1011 C 1100 D 1101 E 1110 F 1111
Example: To convert 11110010110001 into hexadecimal, group the numbers into 4 bits each, if there is shortage of numbers, we can add '0s' at the beginning so that groups of four digits are formed.
0111 1100 1011 0001
7 C B 1
Therefore the hexadecimal equivalent of 111110010110001 is 7CB1.Note that we have added one 0 bit at the left most position to make it a block of 4 bits.
c. Decimal to Hexadecimal Conversion and Vice Versa:
i. Decimal to HexadecimalTo convert a decimal number to hexadecimal , divide the number by 16 until we get '0' . The remainders , in reverse order, are used to code the hexadecimal.
Example: To convert 28436 into hexadecimal number 28436 divided by 16 = 1777 Remainder : 4 1777 divided by 16 = 111 Remainder : 1 111 divided by 16 = 6 Remainder : 15 6 divided by 16 = 0 Remainder : 6
The remainders in reverse order are : 6-15-1-4 which is 6F14 in Hexadecimal (Replace 15 by F).
ii. Hexadecimal to Decimal
To convert hexadecimal to decimal, just multiply the digits with 160, 161, 162 and so on from right to left, and then add the results to get the decimal number.
Example: Convert B61F h to its equivalent decimal value. B61F = B*163+6*162+1*161+F*160
= (11*4096)+(6*256)+(1*16)+(15*1) = 45056+1536+16+15
3. IPv4 Addressing:
An IP address is a unique logical identifier for a node or host connection on an IP network.
An IPv4 address is a 32 bit binary number, and represented as 4 decimal values of 8 bits each. The decimal values range from 0 to 255. This is known as "dotted decimal" notation.
Example: 192.189.210.078
It is sometimes useful to view the values in their binary form. 192 .189 .210 .078
11000000.10111101.11010010.1001110
Every IP address consists of network identifier and node identifier. The IP network is divided based on Class of network. The class of network is determined by the leading bits of the IP address as shown below.
Address Classes
There are 5 different address classes. You can determine which class any IP address is in by examining the first 4 bits of the IP address.
• Class A addresses begin with 0xxx, or 1 to 126 decimal. • Class B addresses begin with 10xx, or 128 to 191 decimal. • Class C addresses begin with 110x, or 192 to 223 decimal. • Class D addresses begin with 1110, or 224 to 239 decimal.
• Class E addresses begin with 1111, or 240 to 254 decimal.
Addresses beginning with 01111111, or 127 decimal, are reserved for loopback and for internal testing on a local machine.
Class D addresses are reserved for multicasting.
Class E addresses are reserved for future use. They should not be used for host addresses.
Now we can see how the Class determines, by default, which part of the IP address belongs to the network (N) and which part belongs to the Host/node (H).
Class A: NNNNNNNN.HHHHHHHH.HHHHHHHH.HHHHHHHH Class B: NNNNNNNN.NNNNNNNN.HHHHHHHH.HHHHHHHH Class C: NNNNNNNN.NNNNNNNN.NNNNNNNN.HHHHHHHH
In the example, 192.189.210.078 is a Class C address so by default the Network part of the address (also known as the Network Address) is defined by the first three octets (192.189.210.XXX) and the node part is defined by the last one octets (XXX.XXX.XXX.078).
In order to specify the network address for a given IP address, the node section is set to all "0"s. In our example, 192.189.210.0 specifies the network address for 192.189.210.078. When the node section is set to all "1"s, it specifies a broadcast that is sent to all hosts on the network. 192.189.210.255 specifies the broadcast address.
b. Private Subnets
There are three IP network addresses reserved for private networks. The addresses are 10.0.0.0/8,
172.16.0.0/12, and 192.168.0.0/16. They can be used by anyone setting up internal IP networks, such as an intranet. Internet routers never forward the private addresses over the public Internet.
4. Subnetting:
Subnetting an IP Network is done primarily for better utilization of available IP address space, and routing purpose. Other reasons include better organization, use of different physical media (such as Ethernet, WAN, etc.), and securing network resources.
A subnet mask enables you to identify the network and node parts of the address. The network bits are represented by the 1s in the mask, and the node bits are represented by the 0s. A logical AND operation between the IP address and the subnet mask provides the Network Address.
For example, using our test IP address and the default Class C subnet mask, we get: 192.189.210.078: 1100 0000.1011 1101.1101 0010.0100 1110 Class C IP Address
255.255.255.000: 1111 1111.1111 1111.1111 1111.0000 0000 Default Class C subnet mask 192.189.210.0 1100 0000 1011 1101 1101 0010 0000 0000
As can be seen above, by using and AND operator, we can compute the network portion of an IP address. The network portion for the IP address given in the above example is 192.189.210.0, and the host portion of the IP address is 078.
CIDR Notation
A Subnetmask normally contains the host portion of the bits also. This is called Classless Inter Domain Routing (CIDR). This will enable more networks for a given class of network address. For example, allowing 3 host bits towards subnet portion in our previous IP address, will allow us to offer 2X2X2 or 8 additional subnetworks. Traditionally, all zeros, and all ones subnets are not used, and hence we are left with 6 subnets.
192.189.210.078: 1100 0000.1011 1101.1101 0010.0100 1110 Class C IP Address
255.255.255.224: 1111 1111.1111 1111.1111 1111.1110 0000 Class C subnet mask with 3 additional bits of host portion used for Subnetting.
Broadcast address: 1100 0000.1011 1101.1101 0010.0101 1111 :192.189.210.95
The above is the broadcast address for a given subnet (192.189.210.078). Under Classful routing, the broadcast address would have been 192.189.210.255.
Note that by using Subnetting, we are able to increase the number of networks available within a given IP address. On the otherhand, we will be loosing the number of hosts available within a subnet to 24 or 16 hosts per subnet. Again, all zeros, and all ones host addresses are traditionally reserved for other purposes.
CIDR (Classless InterDomain Routing) notation: Subnet mask is also represented as below: 192.189.210.078/27, where 27 is the number of bits in the network portion of the IP address. Why use CIDR?
impossible to allocate a classful IP address to every individual or a corporate. Using CIDR, the biggest ISPs are given large pool of IP address space. The ISP's customers such as individual or Corporates are then allocated networks from the big ISP's pool. This kind of arrangement will enable efficient management and utilization of the Internet.
Classful addresses can easily be written in CIDR notation
Class A = A.B.C.D/8, Class B = A.B.C.D/16, and Class C = A.B.C.D/24 Where A,B,C,D are dotted decimal octets.
CIDR Chart
CIDR Block Prefix # Equivalent Class C # of Host Addresses (2ⁿ-2 )
/30 1/128th of a Class C 2 hosts /27 1/8th of a Class C 30 hosts /26 1/4th of a Class C 62 hosts /25 1/2 of a Class C 126 hosts /24 1 Class C 254 hosts /23 2 Class C 510 hosts /22 4 Class C 1022 hosts /21 8 Class C 2046 hosts /20 16 Class C 4094 hosts /19 32 Class C 8190 hosts /18 64 Class C 16382 hosts /17 128 Class C 32766 hosts
/15 512 Class C 131070 hosts
/14 1024 Class C 262142 hosts
/13 2048 Class C 524286 hosts
*Important points to note:
• A subnet mask is used to determine the break between network and host subsections of an IP addressing
• VLSM allows for conservation of address space by allowing the subnet mask to allocate bits across the entire range of the IP address
• An address where all the host bits are set to 1 is the broadcast • An address where all the host bits are set to 0 is the network
• There are 2ⁿ-2 addresses in a CIDR block, where n is the number of host bits
5. DHCP (Dynamic Host Configuration Protocol):
In a TCP/IP network, a host computer needs to be configured for some basic parameters such as IP address, subnet mask, default gateway, etc. There are two ways to configure these TCP/IP network parameters. One is to configure them manually using the workstation's network applet or command prompt. The other is to configure automatically as and when the host computer is switched ON. DHCP is the term used for the automatic configuration of host computers (or workstations). For DHCP to operate, you need a DHCP server that was pre-configured with IP address range and other parameters for passing on to DHCP clients (host computers). The DHCP server provides TCP/IP configuration parameters (IP address, subnet mask, default gateway, etc.) to DHCP client computers. A DHCP server need not be a stand alone machine. It could be a Cisco router or a Linux/Windows server working as a DHCP server as well. Note that the DHCP server itself requires that its TCP/IP network parameters (IP address, subnet mask, etc.) be configured manually.
a. Common DHCP configuration parameters:
Normally the DHCP server provides the client with at least this basic information: • IP Address - This is the client computer IP address
• Subnet Mask - This is the subnet mask to be used by the client computer
• Default Gateway - This is the default gateway to be used by the client computer. Other information can be provided as well, such as Domain Name Service (DNS) server
addresses and Windows Internet Name Service (WINS) server addresses. DNS resolution is the procedure used to resolve an IP address from a domain name. It occurs when a client queries a name server to obtain the IP Address with which it wants to connect. All computers communicate by addressing each other using IP Addresses over any TCP/IP network. So every time we connect to a website or send an email, DNS resolution occurs.
Note: Sometimes, you may want to bypass DNS look up for certain addresses. Then, you can use what is known as HOSTS file to map hostnames to IP addresses. The hosts file contains lines of text consisting of an IP address in the first text field followed by one or more hostnames, each field separated by white space (blanks or tabulation characters).
It is located in " %SystemRoot%\system32\drivers\etc\" on Windows 2003/XP/Vista computers.
Given below is an example of the hosts file. 207.46.197.32 office.microsoft.com 96.0.7.166 practicetests.info
127.0.0.1 localhost loopback ::1 localhost
The following sections describe the DHCP configuration for Windows 7 client computers. It is assumed that the DHCP server computer is already configured and available.
are given below: Using GUI applet
Right-click on " Network" icon on the desktop and click properties which opens "Network and Sharing" window as shown.
Network and Sharing window shows up the basic network information and also shows all the current connections.
Click on "Local Area Connection" on the previous screen that opens Local Area Connection Properties window as shown below
.
Double-click on Internet Protocol Version 4 (TCP/IPv4) option, the window Internet Protocol Version4(TCP/IPv4) Properties shows up as below. If your DHCP is configured with IPv6, please use TCP/IPv6.
Click on "OK" until the network dialogue boxes are closed.
This specific adapter is now set for DHCP. Reboot your system for the changes to take effect. Further, it is assumed that the DHCP server is already configured and present.
Note : These steps are with respect to Windows 7 operating system. Other operating systems like windows 2000/XP etc, the steps are almost the same.
2. Using Command Prompt
• Netsh.exe, dos utility can be used to configure NIC to automatically obtain an IP address from a DHCP server. The command is given below:
netsh interface ip set address "Local Area Connection" dhcp
• To configure DNS and WINS addresses from the Command Prompt, use the following command:
netsh interface ip set dns "Local Area Connection" static 192.168.0.200 • To configure your NIC to dynamically obtain it's DNS settings using
DHCP:
netsh interface ip set dns "Local Area Connection" dhcp
b. Configuring TCP/IP Configuration Settings Manually Without a DHCP
Server:
1. Configure TCP/IP settings using Windows 2000/XP/Vista, and Windows7 Using GUI
Right-click on "Network" icon on the desktop and click properties which opens "Network and Sharing" window as shown.
Now click on "Local Area Connection" that opens Local Area Connection Properties window as shown below
.
Double-click on Internet Protocol Version4(TCP/IPv4) option, the window Internet Protocol Version4(TCP/IPv4) Properties shows up as shown below
Now select the option "Use the following IP Address" and enter the IP Address, Subnet Mask and Default Gateway. Enter the values as required. These values may be obtained from your network administrator.
Note: In a home network environment, the Internet router acts as the default gateway. Therefore, you need to enter the IP address of the router as default gateway on your host computer. The router and your client work station will be in the same subnet. The subnet mask is same as that of the router interface. DNS information is usually optional, and check with your service provider if you need to enter the DNS Server
Click on Ok, also on "Internet Protocol Version4 (TCP/IPv4) Properties" window. Reboot the computer if prompted. Usually, rebooting is not necessary. The settings can then be checked using DOS command "ipconfig".
Note : These steps are with respect to Windows 7 operating system. Other operating systems like windows 2000/XP etc, the steps are almost the same.
2. Configure TCP/IP settings using Windows 2000/XP/Vista, and Windows7 Using Command Prompt
The same thing can be achieved using command prompt utility called netsh.exe. Netsh.exe is a command-line scripting utility that allows you to, either locally or remotely, display or modify the network configuration of a computer that is currently running. In order to configure TCP/IP settings such as the IP address, Subnet Mask, Default Gateway, DNS and WINS addresses and many other options you can use Netsh.exe.
To view TCP/IP settings, use the below command: netsh interface ip show config
Configuration is also easy. The following command configures the interface named Local Area Connection with the static IP address 192.168.0.100, the subnet mask of 255.255.255.0, and a default gateway of 192.168.0.1:
netsh interface ip set address name="Local Area Connection" static 192.168.0.100 255.255.255.0 192.168.0.1 1
6. DOS Utilities For Troubleshooting Network Problems:
DOS (Disk Operating System) controls the computer's hardware and provides an environment for programs to run. Windows computers simulate DOS in virtual environment. There are several DOS utilities that are frequently used for troubleshooting network problems. The subsequent sections discuss these utilities. When there is a network of computers connected in a LAN, then we can use DOS utilities like PING, TRACERT, etc. for testing the connectivity between the workstations and also for troubleshooting the problems.
Given below are some frequently used DOS utilities for troubleshooting network related problems: a. Ping b. Tracert c. Ipconfig d. NBTstat e. netstat, and f. netsh
The first ever step in troubleshooting is testing layer 1 of the OSI model, i.e, verifying the cabling. Ensure that the network connector (usually, RJ-45) is properly connected and the network card LEDs are active.
a. PING:
After verifying the physical connectivity, test the functionality of NIC and the computer for its ability to communicate with networking by using ping to any address on the loopback network (127.0.0.1 to 127.255.255.254). A sample output of pinging the local host is given below:
Next is to test the basic connection between your workstation and default gateway using ping. If the ping to the default gateway is not successful, then check the IP Address, subnet mask, and default gateway address on the workstation and reboot the system if necessary.
A successful ping to default gateway is given below:
Ping sends out a packet to a designated internet host or network computer and measures its response time. The target computer will return (hopefully) a signal. It is often used to test connections on local networks.
b. TRACERT:
The actual path between two computers on the internet consists of numerous segments or "hops" from one intermediate computer to another. Tracert shows each node of the path taken to reach the destination host.
As seen in the above figure, the output contains i. the times for each hop,
ii. the IP addresses for each intermediate computer, and iii.the time taken are displayed.
Tracert shows up to 30 hops. It is convenient for finding if there is one particular segment that is causing a slow or bad connection.
c. IPCONFIG:
IPCONFIG is a command line utility available on windows that gets the IP Address information on a computer, it is an alternative to "winipcfg" utility. The output of the default command contains the IP address, network mask and gateway for all physical and virtual network adapters.
d. IPCONFIG/ALL:
This option displays the same IP addressing information for each adapter as the default option. Additionally, it displays DNS and WINS settings for each adapter.
e. NBTSTAT:
NBTSTAT is a DOS utility that displays protocol statistics and current TCP/IP connections. NBTSTAT is a useful tool for troubleshooting NetBIOS name resolution problems. In a purely TCP/IP network, NBTSTAT is not used.
f. NETSTAT:
NETSTAT is a tool that can be used for checking network configuration and utility. The netstat – a command displays all connections, and netstat –r displays the route table plus active
connections. The netstat –e command displays Ethernet statistics, and netstat –s displays per-protocol statistics.
g. NETSH:
NETSH is a utility that allows you to, either locally or remotely, display or modify the network configuration of a computer that is currently running. In order to configure TCP/IP settings such as the IP address, Subnet Mask, Default Gateway, DNS and WINS addresses and many other options, NETSH.exe can be used.
7. Frequently Used TCP/IP Protocols:
There are a few frequently used TCP/IP protocols that a network administrator needs to be familiar with. Most notable among these are:
a. HTTP b. FTP c. Telnet
d. Email Protocols (SMTP, POP, and IMAP)
a. HTTP (Hyper Text Transfer Protocol):
This is the most widely used protocol on the web. In order to fetch a web page for you, your web browser must "talk" to a web server on the Internet. When web
browsers talk to web servers, they use HTTP protocol (HyperText Transfer Protocol). All browsers use this protocol whether they are Windows based or Linux based.
b. FTP (File Transfer Protocol):
File Transfer Program is used to transfer files from one computer to another. FTP is the most widely used protocol by network administrators for:
i. Taking backups
ii. Uploading or downloading files to/from the server machine
iii.Providing a platform for file storage among many different hosts (such as workstations, routers, servers, etc.)
Note that in order to upload or download a file from FTP site, the login details, FTP username and FTP password must be known. Once connected, files can be transferred
using binary or ASCII mode. However, using anonymous FTP, one can transfer files without supplying login credentials.
The following topics are discussed here:
1. FTP to a Remote Host Using Command Prompt
2. FTP to a Remote Host Using GUI based Software (FileZilla) 1. FTP to a Remote Host Using Command Prompt
FTP can be accessed using "ftp" command on the command prompt, the prompt changes to <ftp> prompt, after which the FTP site can be opened using the command "Open". The user will be prompted for "Username" and "Password", after which the files can be viewed, uploaded or
downloaded.
2. FTP to a Remote Host Using GUI-based Software - FileZilla A software based FTP is almost inevitable for effective control over the file transfer. There are several software based FTP programs available including FileZilla, CuteFTP, SmartFTP, etc. Among these, FileZilla is the most widely used software. It is a free FTP open source solution. It can be downloaded here.
A few useful options available with FileZilla are synchronous browsing (local and remote folders are synchronized with each other), multiple sessions (several FTP sessions can be opened at the same time
transferring 2 or more files at the same time), and storing connections to multiple remote servers so that we don't need to enter the settings again for connecting to remote servers.
c. Telnet:
Telnet is another most widely used application layer protocol in the TCP/IP stack. Telnet is a protocol underlying TCP/IP protocol for accessing remote computers and use the resources present there. On the web, FTP and HTTP protocols allows to request specific files from remote computers but not to actually be logged on as a user of that computer, with telnet it is possible to log on as a regular user with only those privileges that are granted to the specific application and data on that computer.
Note that to telnet to a computer, Username and Password should be known.
1. Telneting to a remote host from command prompt on local work station
Syntax is : telnet open hostname [port]
hostname : specifies the hostname or IP address of the remote computer to connect to
port : Specifies the port number or service name. 2. Telnet Software
There are a number of third-party telnet programs (terminal emulation) available with offering features in addition to the one that comes with the operating system.
Examples to this are Van Dyke CRT program, Putty, etc.
d. Email Protocols (SMTP, POP, and IMAP):
After HTTP, arguably, the most widely used web resource is email. A network administrator configures an email client on host computers quite often, and therefore need to know the functioning and configuration of email client software. The
protocols that are commonly used when accessing email over the Internet or intranet are given below:
• SMTP,
• POP3, and IMAP
SMTP is the protocol used for accessing the Email Server for sending email messages from client computer to the Server, whereas POP and IMAP are used for receiving email messages from the Email Server to the client computer. Note that an Email Server may be a Web Server doing the additional duty of Email Server.
i. SMTP: SMTP stands for Simple Mail Transfer Protocol. It is an "outgoing mail" server that is used for sending email messages from the client computer to the remote mail server. You need to configure your email client with proper SMTP server information for sending messages. SMTP uses port 25.
ii. POP3 and IMAP: POP and IMAP are protocols that are used for fetching email from an Email Server. The main difference between POP and IMAP are that the former does not keep a copy of email messages on the server, whereas IMAP can synchronize with the email folders on the server and maintain a copy of the same locally. The advantage of using IMAP is the ability to roan. You can access the the email server from home as well as office and keep your INBOX, OUTBOX and other folders synchronized using IMAP. POP3 uses port number 110 where as IMAP uses port number 143.
For fetching emails from a remote server, you need to configure an email client such as Outlook or Mozilla Thunderbird.
8. Connectors And Cabling:
Connectors are interfaces for linking devices by using cables. The pins and holes in connectors are usually linked to the electric wires which form the cable. The pin layout describes which pins couple with which wires.
a. DB9:
DB9 connector is an analog 9-pin plug of the D-Subminiature connector family, mainly used for serial connections. The connector is "D" shaped, and easy to recognize.
Actual DB-9 Connector (both Male and Female) Pin Diagram of DB9 Connector
PIN Details
Pin number Name
1 CD - Carrier Detect
2 RXD - Receive Data
3 TXD - Transmit Data
4 DTR - Data Terminal Ready
6 DSR - Data Set Ready 7 RTS - Request To Send 8 CTS - Clear To Send 9 RI - Ring Indicator Shield
b. DB25:
DB25 connector is an analog 25-pin plug of the D-Subminiature connector family, mainly used for serial connections, also used for parallel port connections. DB25 serial ports on computer generally have male connectors, while parallel port connectors are DB25 female plugs.
DB-25 Physical Connector (Male) DB-25 Connector Pin Out
Pins (Serial Connection) Pin number Name
2 TXD - Transmit Data
3 RXD - Receive Data
5 CTS - Clear To Send
6 DSR - Data Set Ready
7 GND - Signal Ground
8 CD - Carrier Detect
20 DTR - Data Terminal Ready
22 RI - Ring Indicator
c. USB:
Universal Serial Bus (USB) is an input-output interface which is much faster than standard serial ports.
PIN Details
Pin number Function
1 Power supply +5V (VBUS) 100mA maximum
2 Data (D-)
3 Data (D+)
4 Ground (GND)
Two kinds of USB connectors:
1. "Type A" connectors, rectangular in shape, generally used for devices which consume little bandwidth
2. "Type B" connectors, square-shaped , generally used for devices with heavy bandwidth requirements
The difference between the two is in the physical layout of pins in the connector. USB "A" plugs are used towards the host system and USB "B" plugs are used towards the USB device.
d. RJ-11:
RJ-11 is a 4-wire connector, commonly used with a modem. It should not be confused with bigger RJ-45 cable and connector. RJ-45 is commonly used for Ethernet network interface card (NIC).
PIN Details Pin # Function A1 Ground A2 Rx (Data Input) A3 Tx (Data Output) A4 Vc (Power)
e. RJ-45:
The RJ-45 connector is commonly used for network cabling and for telephony applications. An RJ-45 connector has 4 pairs of wires as shown in the schematic diagram below. RJ-45 connector is commonly used for Ethernet Networking ports. Devices that normally use RJ-45 ports include NICs, Hubs, Switches, and Routers. It's also used for serial connections in special cases.
PIN Details
Pin Name Description 1 TX_D1+ Transceive data + 2 TX_D1 Transceive data -3 RX_D2+ Receive data + 4 BI_D3+ Bi-directional Data+ 5 BI_D3- Bi-directional Data6 RX_D2 Receive data -7 BI_D4+ Bi-directional Data+ 8 BI_D4- Bi-directional
Data-CABLING
Cisco routers either have RJ-45 based or DB-25 DCE/DTE console and AUX ports. RJ-45 cabling types are
i. Straight-through : Straight-through cable is used for connecting a work station to a hub ii. Crossover : Cross cable is used for connecting two hubs or switches
iii. Rolled : Rollover cable is used to connect console port of cisco router to a pc Identifying a RJ-45 Cable
Hold the two ends of the cable next to one another such that the colored wires can be seen. There are eight colored strips or pins at each end. If the order of the colored pins is same at each end, the cable is straight and if the order of the colors is reversed at each end, the cable is rolled.
i. Straight-Through Cable
RJ-45 Straight-Through Cable Pinouts Signal RJ-45 Pin RJ-45 Pin Signal
Tx+ 1 1 Tx+ Tx– 2 2 Tx– Rx+ 3 3 Rx+ – 4 4 – – 5 5 – Rx– 6 6 Rx– – 7 7 – – 8 8 –
In this, the first (far left) colored wire at one end of the cable is the third colored wire at the other end of the cable.
RJ-45 Crossover Cable Pinouts Signal RJ-45 Pin RJ-45 Pin Signal
Tx+ 1 3 Rx+ Tx– 2 6 Rx– Rx+ 3 1 Tx+ – 4 4 – – 5 5 – Rx– 6 2 Tx– – 7 7 – – 8 8 –
iii. Rolled Cable
In this, the colored wires at one end of the cable are in the reverse sequence of the colored wires at the other end of the cable.
RJ-45 Rolled Cable Pinouts
Signal RJ-45 Pin RJ-45 Pin Signal
– 1 8 – – 2 7 – – 3 6 – – 4 5 – – 5 4 – – 6 3 – – 7 2 – – 8 1 –
f. DB9 to USB:
DB9 connectors are used to link external peripheral devices using serial communication. Some computers, such as laptops do not have DB9/DB25 ports. You may need to convert the
DB9/DB25 to USB for communicating to a router using a laptop computer. Therefore, an adapter cable is required to convert DB9 (or DB25) to USB. Note that, the conversion requires a signal adapter so that DB9 (or DB25) signals are made compatible to USB pinout. It is important to know that the conversion is not a passive process (matching the pinouts) like DB9 to DB25 or RJ-45. This adapter, powered by the USB 2.0 port, takes care of converting from the old serial communications to USB and vice versa. Each USB-RS232 cable contains a small internal electronic circuit board, which is encapsulated into the USB/DB-9 connector.
Connecting a USB to DB9 is a simple task that you can perform with an adapter cable. Steps are given below
1. Purchase a USB to DB9 cable. Remember to note if the cable ends are either male or female. A male cable inserts into a female cable. A male cable has the pins while the female cable has the slots.
2. Plug the male end of the USB adapter cable into the female end of the device you're connecting. Plug and then screw the DB9 end of the adapter cable into the next device.
3. Check the connection by checking the data that you are transferring over the cable. There are numerous applications for using a USB to DB9 adapter cable.
9. Appendix:
a. Troubleshooting Network Interface Card (NIC) For Physical Connectivity:
NIC is the interface between the computer Operating System and the external network, and therefore a critical element in the networking of computers. Typically, an NIC consists of MAC address, and driver software. The driver software is controlled by the TCP/IP protocol residing in the Operating System.As shown in the above diagram, a Network Interface Card consists of a PCI connector (Edge connector) to connect to one of the PC expansion slots, and an RJ-45 connector to connect to external Ethernet. Note that the interface connectors may differ depending upon the expansion bus being used (for example, PCI, ISA, EISA, USB etc.), and the networking media being used (for example, Token Ring, 100BaseT, etc.). The LED indicators provide information about the status of communication.
The D-Link DGE-550SX 1000Base SX Network adapter has two LED indicators:
1. Link indicator (Link: Link up/down). This indicator goes green when the fiber port is connected to the Ethernet network successfully.
2. Activity indicator (ACT - Transmitting/Receiving): When this indicator is blinking green, the network adapter is either transmitting or receiving data to/from the Ethernet network.
b. Modem connectivity and Troubleshooting:
A MODEM (MOdulator-DEModulator) is typically used to send digital data over a phone line. It is a DCE device and connects a computer ( or any other DTE device) to the voice channel (dial-up line). While transmitting the data, modem modulates the data into a signal that is compatible with the phone line, and while receiving the data, the modem demodulates the signal back into digital data.
There are primarily two types of modems. These are: i. Analog modem
ii. Digital modem
i. Analog modems:
diagram below shows an analog modem.
As seen from the above figure, you can use an external modem, internal modem that sits on the internal extension bus such as PCI bus, or and USB modem. For installing an analog modem, you will be needing modem driver software. This software will be different for different Operating Systems and you need to make sure that you have the right version of the driver software loaded on to the computer before attempting to connect to any external host. Usually, the software will also have self testing abilities that can be used for troubleshooting any problems with the installation.
The following features are configured frequently for communicating between hosts using a modem:
1. Speed : The speed at which the modem can send data in bps (bits per second). Typically modem speeds are: 300, 600, 1200, 2400, 4800, 9600, 14.4K, 19.2K, 28.8K bps
2. Auto Dial /Redial : Smart Modems can dial the phone number and & auto redial if a busy signal is received.
3. Auto Answer : Most modems can automatically answer the phone when an incoming call comes in. They have Ring Detect capability.
4. Self-Testing : New modems have self-testing features. They can test the digital connection to the terminal /computer and the analog connection to a remote modem. They can also check the modem's internal electronics.
5. Voice over Data : Voice over Data modems allow a voice conversation to take place while data is being transmitted. This requires both the source and destination modems to have this feature.
6. Synchronous or Asynchronous Transmission : Newer modems allow a choice of synchronous or asynchronous transmission of data. Normally, modem transmission is asynchronous. We send individual characters with just start and stop bits.
Synchronous transmission or packet transmission is used in specific applications. Analog Modems - AT command set and Modem scripts
Analog Modems are used for dial-up connections. Modem configurations vary by manufacturer. They use their own language for communication. The common alphabets of modem speak is given below:
a-z -->“alphabet” * -->“asterisk” ^ -->“carat” - -->“hyphen” $ -->“dollar sign” : -->“colon” % -->“percent sign”
@ -->“character command set” & -->“ampersand”
\ -->“backslash” )--> “parenthesis”
#--> “character command set” 1. AT Command Set
AT commands allows to control many of the functions of modem. AT commands can be used by typing them at the command line of any Terminal program.
See Appendix for AT command set. 2. Writing Modem Scripts
Scripts are those where-in we combine modem-speak commands. Ex: AT&FS0=1&C1&D3&K3&Q9&W
AT&F load factory defaults and settings S0=1 set modem to answer on first ring &C1&D3 set modem up for “action” (cd/dtr) &K3 set hardware flow control
&Q9 set compression
&W save configuration to modem Connecting to a telephone line
When the modem is turned on or after reset, the modem always goes to command state. It enters on-line state after successfully making a connection with a remote modem, either when answering or originating a call. When you return to command state from on-line state, the modem goes to local command state, which allows you to maintain the connection and enter commands.
AT refers to the command prefix (attention sequence) that precedes each command to the modem.
D Dial (Originate mode) : This command signals the modem that the numbers, letters, and commas that follow are all part of a telephone number that it should dial.
T Touch-Tone dialing / Enable tone (DTMF dialing) : When "T" is used as a subcommand of the "D" command (ATDT 12345) this causes all following numbers to be Touch-Tone dialed (default).
When it is used as ATT it sets the default dialing mode to Touch-Tone mode. Can be used in dial string (default). Ex: ATDT15551235 <Enter>
ATDT is the command for dial and enable tone i.e, connecting to a telephone line.
Disconnecting a telephone line
Hn Hook (hang up) When the modem is on-line, you must first enter the +++ escape sequence to take the modem back to command state before issuing the hang up command, ATH. 0 - Forces the modem on-hook. Hangs up the modems
connection to the telephone line and place modem in
command state. 1 - Forces the modem off-hook. After going off hook, operate auxiliary relay.
Ex: ATH 1 <Enter>
ii. Digital Modems :
A digital modem is faster than a analog modem, it does not have to convert between analog and digital signals. The types of digital modems are :
1. ISDN Modem : An ISDN (Integrated Services Digital Network) modem allows the user to connect to the Internet via a dedicated telephone line.
2. DSL Modem : DSL (Digital Subscriber Line) modem uses a copper wire transmission technology to access high speed broadband Internet over telephone lines. For more details on how to install and set up a DSL modem, click here.
3. Cable Modem : Cable modems use fiber optic technology to access the Internet. Cable modems are primarily used to deliver broadband Internet access in the form of cable Internet.
10. Additional Resources:
1. For configuring telnet and ftp on Linux workstation please refer to http://www.cae.wisc.edu/linconftcpip. 2. Modem AT Command Set and Router Configuration Guide:
http://www.cisco.com/en/US/docs/routers/access/modem/AT/Command/reference/atnextpt.html
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