Did You Know?ipconfig utility can be used to find the computer's IP address on Windows as well as on Linux/Unix machines.
Any person with basic knowledge about networking will recognize ipconfig command. This command gives information about the computer's IP address along with the DNS, DHCP, Gateway, and subnet mask addresses. The IP address is needed to carry out further troubleshooting commands. If this command returns a 0.0.0.0 default gateway, then you may be experiencing router problems. You may try the variant of this command, to solve your networking problems. Another extension to the above command is ipconfig/flushdns. This clears DNS cache of any unauthorized IP addresses or technical glitches.
One of the most important commands used in networking is ping. This command is used to check the connectivity between the host and destination. The main advantage of using this troubleshooting command is to find out the problem area in the given network. If you run a ping check from any computer in a network, you will get the status of the router. You will get four replies for your ping query. If you don't get the replies, it indicates problems with your network card or default getaway.
The other advantage of using a ping command is to check the connectivity to any website/Internet. In order to do so, you need to enter the website name after the ping command. If you receive replies from the website, there is virtually no issue. But if you don't, there are chances that you have a faulty cable, DSL modem, or ISP connection problem. To further narrow down on the root cause of the problem, ping 220.127.116.11. If you get replies but are unable to get replies from the website, there is DNS configuration issues.
The traceroute (tracert) command returns the entire path that the data takes to reach the destination. There will be a list of hops that the data makes to reach the destination. If you closely observe, you will see that with every hop the network changes. This means that each network passes the data to another network until it reaches its destination. However, you may observe asterisks in the hop data. The first asterisk that you come across, represents the network which has problems.
Domain Name System (DNS) addresses are mostly the root cause of many networking issues. DNS converts the domain names (like buzzle.com) to their IP address. These IP addresses are needed by the network devices to connect to the Internet or the network. In case there are problems with these addresses, the function of the whole network is hampered. The nslookup command gives a list of IP addresses that are associated with a domain name. If you are unable to get any information regarding the IP address, there are problems with the DNS.
In case of networks, many hosts are connected to a single router. Thus, it becomes a herculean task to check the connectivity of each host in case of network issues. However, at the same time, it is important to check whether the connections (TCP, UDP ports) are active. The netstat command returns the list of all hosts connected to the router and also their status (Listening, Established, Closed, Wait, etc.) By knowing this status, you will know the port number (and IP address) of the TCP/UDP connection that is faulty (in closed or wait state).
The arp command is an external command which is used to identify the problems with IP to Ethernet address conversion. The most common problem that can found out in the arp table is sharing of same IP address by two systems. Two hosts (one of which is definitely the wrong one) are using the same IP address, and chances of the wrong host responding to the IP are high. This will affect your network. You need to check if the Ethernet and IP address pairs are correct. For this, you should make a list of each host's Ethernet address. By comparing your list and the table displayed by arp command, you can identify the problem (host) easily.