Computer networking

Configuration of Static/Dynamic NAT in Cisco Router Static NAT (Network Address Translation) is one-to-one mapping of a private IP address to a public IP address. Static NAT (Network Address Translation) is useful when a network device inside a private network needs to be accessible from internet. In order to configure NAT we have to understand four basic terms; inside local, inside global, outside local and outside global. These terms define which address will be mapped with which address. Term : Description Inside Local IP Address : Before translation source IP address located inside the local network. Inside Global IP Address : After translation source IP address located outside the local network. Outside Global IP Address: Before translation destination IP address located outside the remote network. Outside Local IP Address : After translation destination IP address locat...

Star Topology using HUB and Switch, IP configuration of end devices, show command, copy command, password setting, hostname setting Steps to Implement : Connect 5 PC’s to a switch through fast ethernet cables and connect the switch to a router using a Gigabyte ethernet cable. Assing an IP to all the PC’s i.e Topology     PC 0 – 192.168.1.1     PC 1 – 192.168.1.2     PC 2 – 192.168.1.3     PC 3 – 192.168.1.4     PC 4 – 192.168.1.5 3. Configure the router : Router>enable Router# configure terminal Router(config)#hostname R1 R1(config)#interface gig0/1 R1(config-if)#ip address 192.168.1.1 255.255.255.0 R1(config-if)#exit R1#configure terminal R1(config)#line console 0 R1(config-line)#password cisco R1(config-line)#login R1(config-line)#exit R1(config)#enable password cisco R1(config)#hostname harsh hardik(config)#exit hardik#write h...

Packet Tracer Simulation – TCP and UDP Communications Part 1: Generate Network Traffic in Simulation Mode Step 1: Generate traffic to populate Address Resolution Protocol (ARP) tables.  Click MultiServer and click the Desktop tab > Command Prompt.  Enter the ping 192.168.1.255 command. This will take a few seconds as every device on the network responds to MultiServer.  Close the MultiServer window. Step 2: Generate web (HTTP) traffic.  Switch to Simulation mode.  Click HTTP Client and click the Desktop tab > Web Browser.  In the URL field, enter 192.168.1.254 and click Go. Envelopes (PDUs) will appear in the simulation window.  Minimize, but do not close, the HTTP Client configuration window. Step 3: Generate FTP traffic.  Click FTP Client and click the Desktop tab > Command Prompt.  Enter the ftp 192.168.1.254 command. PDUs will appear in the simulation window.  Minim...

Networking – SocketProgramming in TCP. Python provides two levels of access to network services. At a low level, you can access the basic socket support in the underlying operating system, which allows you to implement clients and servers for both connection-oriented and connectionless protocols. Python also has libraries that provide higher-level access to specific application-level network protocols, such as FTP, HTTP, and so on. What is Sockets? Sockets are the endpoints of a bidirectional communications channel. Sockets may communicate within a process, between processes on the same machine, or between processes on different continents. Sockets may be implemented over a number of different channel types: Unix domain sockets, TCP, UDP, and so on. The socket library provides specific classes for handling the common transports as well as a generic interface for handling the rest. Sockets have their own vocabulary − ...

Network Utilities-
 ifconfig, traceroute, netstat, ping, arp   1. ifconfig stands for “interface configuration”. It is used to view and change the configuration of the network interfaces on your system. Options : a : view the configuration of all network interfaces on the system.  eth0 : view the configuration of a specific interface, specify its name as an option. wlan0 down : disable an active network interface using the down keyword. 2. Traceroute attempts to trace the route an IP packet would follow to some Internet host by launching probe packets with a small ttl (time to live) then listening for an ICMP “time exceeded” reply from a gateway. It start its probes with a ttl of one and increases this by one until it gets an ICMP “port unreachable” (or TCP reset), which means we got to the “host”, or hit a max (which defaults to 30 hops). Options : 4 ,6 : Explicitly force IPv4 or IPv6 tracerouting. F : Do n...