This is the first session on the course “Inter-networking with Linux”. This session gives an overview of the TCP/IP stack, the working of different layers and the addresses used on each. This session gives specific emphasis on the Internet Layer addresses, the class-full addresses, and the classless internet domain routing. It also describes the importance of private addresses and briefly touches upon the concepts of sub-netting and super-netting. The concepts used in this session are very important for all the upcoming lectures…

This session will cover setting up of the lab environment for the rest of the sessions, using three machines. One running Ubuntu server, and other two running Kali Linux and Windows XP. It will cover making a network of these machines by assigning them TCP/IP parameters statically using shell commands temporarily and then by writing these TCP/IP parameters in the configuration files. Finally will ping these files using ip addresses and names to confirm connectivity.

This session is a continuation of previous session of setting up the Lab environment. It will cover understanding and configuring the DHCP server on a home router. It will also cover as how to install, configure and use DHCP server on Ubuntu Server machine, and using the system daemon to manage various services. The underlying details of how a DHCP server actually works are also covered.

This session covers installing, configuring and using telnet server (on a Ubuntu Server machine). It is also shown as how we can run telnet service under xinetd (extended internet daemon). The telnet server is accessed using telnet client running on a Linux client as well as a Windows client. It also covers how telnet communication is unsecure and proves this using wireshark (a packet sniffer that capture NW packets in real time and display them in human readable format).

This session deals with some important cryptographic terms that are required to fully understand some of our future sessions that cover cryptographic network protocols like ssh, ftps and https. The major terms discussed are encoding, hashing and symmetric encryption. The famous Linux tool openssl is used for calculating different hashes. Two uses of hashing are also discussed, i.e., storing passwords and ensuring data integrity. Finally, a practical hands-on example is used to understand symmetric encryption on a Linux terminal.

This session is a continuation of previous session on cryptography. It completes the discussion with a hands-on example on asymmetric encryption and the use of digital signatures. Finally, the use of Diffie-Hellman algorithm (for key exchange) is discussed. The session is concluded with the concept and use of Digital certificates.
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This session deals with installing, configuring, and using ssh server. The three stages of connectivity are described in detail with hands on practice. Stage1: Negotiating secure connection and secret key using asymmetric encryption. Stage2: Authenticating user, via password or using ssl keys. Stage3: The actual data transfer using symmetric encryption. As a bonus finally the use of secure copy (scp) command is also explained.

This session deals with the famous File Transfer Protocol. The working of FTP is described with a discussion on different available FTP-client and FTP-server programs (both GUI based as well as CLI based). The vsftpd server is installed and configured on Ubuntu Server. The FTP server was run using xinetd as well as in stand alone mode. Finally, a login demonstration was shown using anonymous as well as a local user from a machine running Kali Linux to Ubuntu Server running vsftpd server.

This session is a continuation of previous session FTP session. Different file operations are carried out to upload, download, delete and create files on the remote machine. This is done using ftp command line client program as well as GUI program FileZilla. To show the security loop hole in ftp, wireshark is used to snoop the data in transit. Finally, vsftpd is configured to work over SSL/TLS to achieve security. The use of different cipher suites, hashing and digital certificates are discussed and shown practically.