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NETWORK BASICS

Network A system of interconnected computers and computerized peripherals such as printers is called computer network. This interconnection among computers facilitates information sharing among them. Computers may connect to each other by either wired or wireless media. A computer network consists of a collection of computers, printers and other equipment that is connected together so that they can communicate with each other.  


Network application
A Network application is any application running on one host and provides a communication to another application running on a different host, the application may use an existing application layer protocols such as: HTTP(e.g. the Browser and web server), SMTP(e.g. the email-client). And may be the application does not use any existing protocols and depends on the socket programming to communicate to another application. So the web application is a type of the network applications. 
There are lots of advantages from build up a network, but the th…

COMMAND LINE INTERFACE

COMMAND LINE INTERFACEMost of us are running Transmission Control Protocol/Internet Protocol (TCP/IP) Version 4 on our networks these days so we absolutely need a way to test IP connectivity. But we also need be able to test and verify IPv6 networks. The reason for this is that even though Microsoft makes the majority of client platforms, a lot of these commands are really platform independent, and most of them can now use both IPv4 and IPv6. Even so, keep in mind that the Network+ exam focuses on the basic concepts of the function and use of the TCP/IP utilities that come with Windows. You can use several utilities to verify TCP/IP function on Windows workstations, and Most of them are listed in the chapter objectives. 



Is used to find out your current TCP/IP settings. With IPCONFIG you can find out your IP Address, find your Default Gateway and find your Subnet Mask. This is a very handy network tool for finding your local IP address. 
ipconfig /all 
To display all your IP information for all adapters. With ipconfig /all you can also find out your DNS Server and MAC Address. This will show your full TCP/IP configuration for all adapters on your Windows machine. You can find out your own IP Address as well as your default gateway. 
ipconfig /release To release your current IP information and obtain a new IP Address from the DHCP server. 

ipconfig /renew Used to renew your IP Address if you have it set to obtain IP Address automatically. 

ipconfig /displaydns This shows your current DNS Resolver Cache Logs

ipconfig /flushdns This flushes or clears your current DNS Resolver Cache Logs. To ensure Windows is getting addresses from the new DNS servers instead of using old, cached entries, run the ipconfig /flushdns command after changing your DNS server. 

ipconfig /registerdns The register DNS command updates the DNS settings on the Windows computer. It doesn't just access the local DNS cache, it initiates communication with the DNS server and the DHCP server so it can re-register the network address. You can use this for troubleshooting problems with connection to the ISP (Internet Service Provider), like failing to obtain a dynamic IP address from the DHCP Server or failing to connect to the ISP DNS server. 
If you ever wonder "what your IP Address is" you would run an ipconfig as shown above. If you need to find your IP address, default gateway(router login) or subnet mask ip config is the tool to use. These numbers can be very helpful when trouble shooting your local network connection. If you have changed your settings but they are not taking place you may try a ipconfig release and renew. If you're having problems resolving to a website you may try flushing your DNS Resolver Logs.  
PING Command 
In all of these examples "xxx.xxx.xxx.xxx" is an example of a Domain Name or an IP Address. You must fill those out yourself. 

ping xxx.xxx.xxx.xxx  To Ping an IP Address you would type the following DOS Command in the Windows Command Prompt. Ping followed by an IP address. That is how you do an internet ping. 

ping site.com (web address) To ping a website you would type ping followed by the website domain name. If you know the websites IP Address you can ping it too. 
Ping Command Switches 
ping xxx.xxx.xx.xx –t 
Continuous Ping - It will keep on pinging forever until you hit Ctrl + C to stop it. This can be great for troubleshooting intermittent connections. Just open up a Command Prompt (or 3) and run the continuous ping command on a site like Google.com to see when youre dropping packets. 

ping xxx.xxx.xx.xx -n 10 

Number of Pings - The N Switch is simply for setting the number of pings. By default the ping cmd sends out 4 packets at 32 bytes each. 
ping xxx.xxx.xx.xx -l 1500 

Size of Packet - By default the packets sent are a small 32 bytes. You can set your own  size up to the max 65500 bytes. This can really help for stress testing your local network. 

ping xxx.xxx.xx.xx -w 5000 Time Out - This is in milliseconds. The timeout by default is 4,000 milliseconds which amounts to 4 minutes. Just seeing if you were still paying attention. It really is only 4 seconds. 

ping -a xxx.xxx.xx.xx Resolves Hostname Address - This is a great one if you are helping someone else and need to find out what router model they are using. You an resolve the host of an IP Address with this command. Try pinging your router or your local computer with it. ping -a 127.0.0.1. Not this switch will only work in front of the IP Address. Ping Command 

Summary 

The Ping command is a network tool used to determine if you are able to send packets between your network computer on the internet to another computer without losing packets along the way. By doing this you can determine if you're online or if a website is down. It also calculates round trip time and Time to Live. This can let you know if your NIC card is working properly and if you're able to reach your router or modem. It can also be used as a network tool for troubleshooting. 
Networking Basics Command Prompt 
tracert site.com With Trace route you can trace the path your packets take across the internet from you to your destination. Along the way you can determine the time from hop to hop. You can identify server problems and latency with this tool. It really helps see where the failure is between you and a destination. 

nslookup site.com nslookup xxx.xxx.xxx.xxx 
nslookup is a way to get the IP address for a domain name. You can also do a reverse lookup from Domain Name to IP Address. It can be a way to find out if your DNS is properly working or if the site is having problems. You can obtain an IP from a site and try to visit the IP directly, bypassing the Domain Name Servers that would usually resolve the Domain name to IP name. 

netstat netstat can be used to view your active network connections and TCP/IP connections. You can determine what ports are open and being used, what programs are using your ports and what kind of TCP and UDP connections are present. Looking in here for the first time may scare the hell out of you. 
Netstat switches netstat -a Displays all active TCP connections. And TCP / UDP ports. netstat -e Displays Ethernet statistics. Netstat -b displays all active programs that are listening. 

netsh is used to reset or rebuild the Windows TCP/IP IP Stack. This can be done if you have a problem with DNS. Say you are able to browse to a sites IP address but not to its Domain Name. You can find the sites IP by using nslookup mentioned above. You may need to run this command as an administrator by right clicking, run as admin for elevated permissions. 
getmac How do I find my MAC Address you might ask? If you open up the command prompt you simply type getmac.  
arp -a This command can be used to find out the MAC address of the device you are connecting to. With this information, you can find out what type of router you are connected to by using this website. 


Most Linux drives come in zip format. You can extract them with tar utility. You can obtain LAN driver directly from manufactures sites or form other media like motherboard CD. 
We assume that you have LAN driver and copied it in your root directory. Extract driver file with tar utility and change directory to extracted folder Every LAN driver have a readme file telling the way to install that driver 
(Note:- driver will compile only if you have proper compiler, we recommended that you install gcc compiler during installation. ) To install driver execute these commands as shown here or use readme files /etc/resolv.conf  This file contain information about DNS server. You can set DNS ip in this files. Each nameserver line represents a DNS server, and the search line specifies domain names to try if only the first part of a hostname is used. 
/etc/modprobe.conf  The first line assigns the e100 kernel module to the eth0 network device. If the network card is supported, the module is automatically configured during installation or by Kudzu the first time the system is booted with the new card. /etc/hosts 

File lists IP addresses and hostnames that should resolve to the IP addresses. The first one listed, 127.0.0.1, is referred to as the loopback interface and should never be removed. If some hostnames cannot be resolved by the DNS servers, list them with their IP addresses after the loopback device. 
/etc/sysconfig/networking/devices 

File contain the list of all detected and install LAN card. This is the location of all networking scripts. You can create new virtual LAN card in this directory. even you can change IP configurations and default booting behavior of LAN card by directly editing in files. 
/etc/sysconfig/network 

This file is mostly used to change hostname permanently. If the NETWORKING option is set to yes, the networking subsystem is enabled but not necessarily started at boot time. The value of the HOSTNAME option is the hostname for the system. If one is not set, the default hostname is localhost. Refer to the file /usr/share/doc/initscripts-<version>/sysconfig.txt for additional options for this file. 

/etc/sysconfig/network-scripts/ 

In the /etc/sysconfig/network-scripts/ directory, each network device has its own configuration file with the filename ifcfg-<devicename> such as ifcfg-eth0 for the first Ethernet device. If the device is configured for a static IP address, the interface configuration file looks similar to image given below. If the ONBOOT option is set to yes, the device is activated at boot time using the network initialization script. 
/
Linux command to uninstall virtual interfaces or network aliases 
Use ifconfig command. It is used to remove virtual interfaces or network aliases. 
ifconfig is used to configure the kernel-resident network interfaces. It is used at boot time to set up interfaces as necessary. After that, it is usually only needed when debugging or when system tuning is needed. 
Type the command to remove eth0:1: 

/etc/sysconfig/network-scripts/ifcfg-ethX-range0 file 

To remove interface permanently edit network configuration file stored at /etc/directory. For Red Hat / Fedora Core file stored in /etc/sysconfig/network-scripts/ directory. For Debian or Ubuntu Linux just edit file /etc/network/interfaces and remove the entries. For example open file called /etc/sysconfig/networkscripts/ifcfg-eth1-range0 





  • Use loopback test command 
  • Find your IP address by using command. 
  • Find your MAC address by using command. 



a) ping  
b) ipconfig  
c) ipconfig /all  
d) tracert 


a) Workstation configuration 
b) Connectivity 
c) Patch cable 
d)Server configuration 


a) Accessing the intranet from your workstation 
b) Accessing the intranet from the user’s workstation as yourself 
c) Replacing the patch cable on the workstation 
d) Asking another user to access the intranet from the problem user’s workstation 


a) Run tracert from a workstation.
b) Check the server console for user connections. 
c) Run netstat on all workstations. 
d) Check the network diagnostics. 


a) Insufficient rights to access the server 
b) A bad patch cable 
c) Server down 
d)Wrong username and password 


 a) The Caps Lock key is pressed. 
b) The network hub is malfunctioning. 
c) You have a downed server. 
d)You have a jabbering NIC. 

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