Network Diagnostic Commands

NT's best-kept secrets

This month, I'll share my top 10 Windows NT network diagnostic commands. I use these commands to troubleshoot network connection problems. You run these commands from the command line. The commands might be new to the novice administrator, but they will be familiar to the experienced administrator.

10. Net Session displays your system's open named pipe connections. You can use named pipes to connect to SQL Server. To run the Net Session command, enter

net session

9. Nslookup is a diagnostic tool that displays information from Domain Name System (DNS) name servers. You can use the tool to troubleshoot DNS setup problems. You typically run Nslookup as an interactive utility that displays a command prompt that lets you run specific Nslookup subcommands. To start Nslookup, enter

nslookup

8. Arp resolves TCP/IP to media access control (MAC) addresses. All network protocols must use the MAC hardware address to connect to a remote system. The Arp command works only if you have an address translation table. To display the Ethernet address of a TCP/IP system with the IP address of 192.168.100.2, enter

arp -a 192.168.100.2

7. Nbtstat displays statistics and connections about systems that are using NetBIOS over TCP/IP. You use the ­a switch to list the NetBIOS name table for a remote computer. You can also reload any LMHOSTS file by using the ­R switch. To display all NetBIOS over TCP/IP sessions on the system, enter

nbtstat -s

6. Tracert is a utility you can use to verify that a router path exists between your system and a remote system. Tracert reports the number of hops required to get to a certain destination and the router at each hop. To trace the router to a system with the name myhost, enter

tracert myhost

5. Ipconfig displays your system's TCP/IP configuration settings. Ipconfig also reports the address of your DNS and Windows Internet Naming Service (WINS) servers. To display all TCP/IP settings, enter

ipconfig /all

4. Route Print displays NT's routing table. The Route Print command shows you the default routes that NT uses, and the routes to remote systems on the Routing Information Protocol (RIP). To run Route Print, enter

route print

3. Telnet lets you connect to a specific port on a remote system and find out whether a socket application is listening on that port. To run Telnet, select Start, Programs, Accessories, Telnet. Alternatively, open a command prompt and enter

telnet

2. Netstat displays the connection status and statistics of your TCP/IP or UDP connections. The Netstat command shows the local name, remote name, and port of your active network connections and their current state. You use the ­a switch to include your system's server connections, the ­r switch to display routing information, and the ­s switch to display protocol statistics. To run the Netstat command, enter

netstat

1. Ping is my favorite network diagnostic tool. Ping works with all TCP/IP systems and identifies basic network connectivity problems. The Ping command uses Internet Control Message Protocol (ICMP) to send a packet of data to a remote host, then waits for the host to bounce the packet back. Ping checks for data validity and calculates the round-trip time. Ping can use the host name or IP address. To ping a system with the IP address of 192.168.100.2, enter

ping 192.168.100.2