Computer networking

OSPF Routing Protocol Open Shortest Path First ( OSPF ) protocol  for Internet  Protocol  (IP) networks. It uses a link state routing (LSR) algorithm and falls into the group of interior gateway  protocols  (IGPs), operating within a single autonomous system (AS). It is defined as  OSPF  Version 2 in RFC 2328 (1998) for IPv4. OSPF supports/provides/advantages – Both IPv4 and IPv6 routed protocols Load balancing with equal cost routes for same destination VLSM and route summarization Unlimited hop counts Trigger updates for fast convergence A loop free topology using SPF algorithm Run on most routers Classless protocol There are some disadvantages of OSPF like, it requires extra CPU process to run SPF algorithm, requires more RAM to store adjacency topology and more complex to setup and hard to troubleshoot. the topology / Configuration Now, configuring OSPF for R1. R1(config)#router ospf 1 R1(co...

About Cisco packet tracer Packet Tracer is a cross-platform visual simulation tool designed by Cisco Systems that allows users to create network topologies and imitate modern computer networks. The software allows users to simulate the configuration of Cisco routers and switches using a simulated command line interface. Packet Tracer makes use of a drag and drop user interface, allowing users to add and remove simulated network devices as they see fit. Key Features   Packet Tracer Works-paces: Cisco Packet Tracer has two work- spaces—logical and physical. The logical workspace allows users to build logical network topologies by placing, connecting, and clustering virtual network devices. The physical workspace pro vides a graphical physical dimension of the logical network, giving a sense of scale and placement in how network devices such as routers, switches, and hosts would look in a real environment. The physical view also provides geographic representations of...

Configuration of Routing Information Protocol Routing Information Protocol  ( RIP ) is a dynamic  routing protocol  which uses hop count as a  routing  metric to find the best path between the source and the destination network. It is a distance vector  routing protocol  which has AD value 120 and works on the application layer of OSI model.  RIP  uses port number 520. Features of RIP 1. Updates of the network are exchanged periodically. 2. Updates (routing information) are always broadcast. 3. Full routing tables are sent in updates. 4. Routers always trust on routing information received from neighbor routers. This is also known as  Routing on rumours . RIP versions :  There are three vesions of routing information protocol –  RIP Version1 ,  RIP Version2  and  RIPng . RIP v1  is known as  Classful  Routing Protocol because it doesn’t send information of subnet mask in...

Router mode , switch/router basic commands ROUTER : A router is a device that analyses the contents of data packets transmitted within a network or to another network. Routers determine whether the source and destination are destination are on the same network or whether data must be transferred from one network type to another, which requires encapsulation the data packet with routing protocol header information for the new network type. Routing is a process which is performed by layer 3 (or Network Layer) devices in order to deliver the packet by choosing an optimal path from one to another. Advantages No Routing overhead for router CPU which means a cheaper router can be used to do routing. It adds security because the only administrator can allow routing to a particular network only. No bandwidth usage between routers. Disadvantages For a large network, it is a hectic task for an administrator to manually add each router for the netw...

Socket Programming using UDP Socket.   The user datagram protocol (UDP) works differently from TCP/IP. Where TCP is a stream oriented protocol, ensuring that all of the data is transmitted in the right order, UDP is a message oriented protocol. UDP does not require a long-lived connection, so setting up a UDP socket is a little simpler. On the other hand, UDP messages must fit within a single packet (for IPv4, that means they can only hold 65,507 bytes because the 65,535 byte packet also includes header information) and delivery is not guaranteed as it is with TCP. Server import socket import sys sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM) server_address = (‘localhost’, 10000) print >>sys.stderr, ‘starting up on %s port %s’ % server_address sock.bind(server_address) while True:     print >>sys.stderr, ‘\nwaiting to receive message’     data, addres...

IMPLEMENTATION OF DHCP IN CISCO PACKET TRACER The Dynamic Host Configuration Protocol (DHCP) is a  network management protocol  used on  UDP/IP  networks whereby a DHCP server dynamically assigns an  IP address  and other network configuration parameters to each device on a network so they can communicate with other IP networks. A DHCP server enables computers to request IP addresses and networking parameters automatically from the  Internet service provider  (ISP), reducing the need for a  network administrator  or a user to manually assign IP addresses to all network devices.In the absence of a DHCP server, a computer or other device on the network needs to be manually assigned an IP address, or to assign itself an  APIPA  address, which will not enable it to communicate outside its local subnet. DHCP can be implemented on networks ranging in size from  home networks  ...

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...