8. DOS : Summary of the most common network commands
1. Verify a connection - 2. Various audits - 3. Internet connection
The two previous chapters have toured most of the DOS commands for networks. I resumed here the essential controls with the most commonly used options for troubleshooting a LAN or Internet connection.
1. Check connection
1.1. The card has an IP address defined
| IPCONFIG displays a summary of the IP of the network card properties |
1.2. If TCP/IP is installed correctly on the computer
| PING 127.0.0.1 sends a ping internally |
The IP address 127.0.0.1 is the local address (localhost) of the network adapter. If the command returns timed out, the TCP/IP configuration is in error. This requires a repair or a reinstallation of the network portion of the computer. This command requires no physical network connection (Ethernet cable or wireless) with other computers...
1.3. A communication in an internal network can established.
| PING X.X.X.X sends a ping command to the NIC whose IP address is X.X.X.X. |
1.4. A communication to the Internet may be.
| PING www.site.com sends a ping a domain name. |
This option uses the DNS servers. This command can be used if the connection to the internal network is established but no page appears in the browser. This problem occurs when the DNS server is poorly informed. In this case, you can use IPCONFIG /ALL. You can also empty the cache by:
| IPCONFIG/FLUSHDNS empty the cache of DNS (from Windows 2000) resolution |
2. Checks
2.1. What are the active connections?
| ARP-a displays the match IP / mac address of computers and connected devices. Dynamic connections use DHCP to configure the IP address. |
NET View also allows to display the computers on the network but its NETBIOS name and not its IP address. Another difference is that here the PC where hand order is filled (but not the router, here in 192.168.1.2.).
2.2. What are the shared resources.
First use the NET VIEW command to check what are the possible computers. Once determined, use the command NET VIEW \\computername. Note, this command works for all computers in the same workgroup or in the same domain.
2.3. Which connected users on computer?
| NET session: displays the connections on a computer, including other computers. |
2.4. What TCP and UDP ports to the listening on a computer?
| NetStat will display all active (tuned) ports on a computer both TCP and UDP. It allows for example to detect trojans and other malicious programs. |
| NetStat-a to display all ports on a computer both TCP and UDP, including those who are inactive. |
3. Internet connection
Verify the name of a site using its IP address is not possible directly by typing the IP address in the address bar of your INTERNET browser (Explorer, Firefox,...), except in a few special cases. If the site does not too secure firewall, you can use the TRACERT command.
| TRACERT X.X.X.X to display jumps when connecting to the IP X.X.X.X, IP addresses and host name address. |