Networking in Linux

♦ Introduction A computer network is defined as a number of systems that are connected to each other and exchange information across the network connection. The system network is configured by setting the IP address which is assigned by the system administrator. The IP address provides base services for transmitting data between networks in TCP/IP (Transmission control protocol/Internet protocol). ♦ Topics ► Network Connectivity ► IP address ► Accessing Remote system ► Transferring files ► Internet configuration

Networking in Linux ♦ The Linux system can be connected to the network with the help of network hardware. ♦ Network hardware can be LAN (Local area network) card, cables, hub/switch or router. To configure the network for the system, TCP/IP (Transmission Control Protocol/Internet Protocol) address is required from the system administrator. ♦ The IP address can also be obtained from the DHCP (Dynamic host configuration protocol) server configured by the system administrator. ♦ When the system is connected to the network, the resources can be shared and data can be transferred among the systems. ♦ The LAN services (telnet, SSH - Secure Shell, FTP – File transfer protocol) enables the file transfer and remote login to the system. Networking in Linux

IP Address ♦ An IP address is a 32 bit binary number usually represented as 4 decimal values, each representing 8 bits, in the range 0 to 255 (known as octets) separated by decimal points. ♦ Every system in network is assigned a unique identifying number called IP address. ♦ It is used in order to identify and communicate with different systems present in the network. ♦ The data is sent across the network and contains a source and destination IP address. ► Example: ► ► ►

Networking in Linux ♦ Configuring IP address The system can be a part of network by configuring the IP address. The IP address can be set by two options in CUI mode and GUI mode. ► Static IP ► Dynamic IP (DHCP) IP Address

Networking in Linux IP Address ♦ Static IP: A static IP address is configured manually by physically entering the IP address in configuration dialog box and it does not change until altered manually. The static IP is assigned by the system administrator. ♦ Dynamic IP: In a large computer network, the process of assigning IP address is simplified using a DHCP server. A DHCP server is used to automatically assign the IP address to the computers that are configured as a DHCP client. ♦ The following commands are used to configure and verify the IP address from the command line prompt. ► netconfig ► service network restart ► ifconfig ► ping

Networking in Linux ♦ Static IP address in CUI mode ♦ Configuration of the static IP address ► Syntax Type the command # netconfig (Press Enter key) at the command prompt in the terminal window. IP Address

Networking in Linux ♦ network service ► Syntax # service network restart IP Address

Networking in Linux IP Address ♦ # ifconfig

Networking in Linux IP Address ♦ # ping

Networking in Linux IP Address ♦ Dynamic IP address in CUI mode ♦ Configuration of the dynamic IP address ► Syntax # netconfig (Press Enter key)

Networking in Linux ♦ Static IP address in GUI mode ♦ Network configuration in static IP IP Address

Networking in Linux ♦ Dynamic IP address in GUI mode ♦ DHCP settings IP Address

Networking in Linux IP Address ♦ Host Name A hostname is the unique name assigned to each host on the network. The hostname is used to identify a particular IP address. Hostnames are used by various naming systems like telnet, ssh, FTP, GFTP, NIS and DNS. ► There are three ways to resolve host names to IP addresses on a Linux system: /etc/hosts DNS (Domain name service) NIS (Network information service) Contd…

Networking in Linux ♦ etc/hosts is a configuration file maintained locally on each host to resolve hostnames to IP addresses. On a small network, it is easy to maintain the name resolution of hostnames to addresses. When adding or removing hosts, or reassigning IP addresses, the user have to update the /etc/hosts file. ♦ DNS (Domain name service) will resolve the host names into IP addresses in a large network. ♦ NIS (Network information service) provides a central point of administration for common configuration files like /etc/passwd, /etc/hosts. It preserves the consistency of the configuration files across all the systems on the network. It simplifies configuration file updates considerably. IP Address

Networking in Linux ♦ Systems in the network can be accessed remotely with help of network connectivity and using IP addresses in two ways: ► Telnet ► SSH ► Telnet Telnet is a terminal program for TCP/IP networks such as the Internet. The telnet program runs on your computer and connects your system to the other system present in the network. To start a telnet session, you must log in to other system by entering a valid username and password of the other system. Contd… Accessing Remote System

Networking in Linux Contd… Accessing Remote System ♦ telnet session ► Syntax # telnet

Networking in Linux ♦ SSH SSH is a program for logging into a remote machine and for executing commands on a remote machine ► The root user can login through SSH and execute the system administrative command. ssh command ► Syntax ssh Accessing Remote System

Networking in Linux Transferring files ♦ Files can be transferred among various systems in the network by using FTP, GFTP and SCP (secure copy). ► FTP FTP (File transfer protocol) is a program that allows you to transfer the files between computers present in the network. It can also transfer the files among different operating systems. Example: Linux to Linux, Linux to Windows, Windows to Linux. Syntax # lftp

Networking in Linux ♦ GFTP GFTP (Graphical file transfer protocol) is the tool used for uploading and downloading the files in a graphical mode. ♦ GFTP (Graphical file transfer protocol) session Contd… Transferring files

Networking in Linux Transferring files ♦ SCP (secure copy) ► The scp command is used to copy the files from other system present in network. ► Syntax # scp : ► Example: scp file :/root

Networking in Linux Internet configuration ♦ In Linux, internet can be browsed both in GUI mode as well as CUI mode. The internet can be configured after the network connectivity. ► Configuring internet in GUI mode ► Step 1: Web browser (Mozilla)

Networking in Linux ♦ Step 2: Proxy configuration Internet configuration Contd…

Networking in Linux ♦ Step 3: Setting the proxy IP and the port number Contd… Internet configuration

Networking in Linux Contd… ♦ Step 4: Verifying the Internet connectivity Internet configuration

Networking in Linux ♦ Modem ► Modem (stands for modulator-demodulator) is a device that enables a system to transmit data over telephone lines for internet connectivity. ► It converts digital computer signals into analog format for transmission of data. Internet configuration

Networking in Linux Internet configuration ♦ Connection to internet through modem

Networking in Linux Lab Exercise ♦ How to configure the IP address in CUI mode? Assume that your system administrator or lab in-charge has given you the IP Address as ? ♦ Check your system to be a part of network and communicate with other systems present in the work ♦ Configure your system with Dynamic IP Address using DHCP ♦ Name the command to copy the files among the system in the network with out using ftp?