Question :
What are the best steps to take in troubleshooting TCP/IP connectivity on a Windows network?
Answer :
In a Windows TCP/IP environment, network configuration problems inevitably arise. Often the problem can be traced to an improperly configured TCP/IP setting, but finding the culprit can be difficult. Below are some steps to help determine where the problem exists:
1. What stopped working? The client, server, or the printer? Ask around to learn if the outage is affecting others or just a single desktop.
2. If the server stopped working, you should notice other co-workers with similar problems. If this is the case, focus on fixing the server.
3. If a single client PC has stopped responding to the network, ask the user whether new software was just loaded or any recent changes have been made to the system, including the installation of service packs, new Internet software, video games, and so on.
4. Check the physical network. The physical topology of your network is most prone to failure. In fact, most network problems are often due to Physical Layer failures (cabling, etc).
5. Is it plugged in? Check all network cable connections. Start at the NIC. Is there a green link light? Check the wiring closet to see if someone "borrowed" the patch cable. Check the hub to see if the system is getting a link across the cable.
6. If you don't have a cable tester, get one. Cabling is very susceptible to electricians, cleaning people and so on.
7. Start PINGing. Windows TCP/IP has the PING command built in. In a typical network you have this order (client->gateway->server) or (client->gateway->internet). First, attempt to PING yourself from the Windows command prompt. Your local "loopback" address for such testing is 127.0.0.1.
Example:
C:\WINDOWS>PING 127.0.0.1
PINGing 127.0.0.1 with 32 bytes of data:
Reply from 127.0.0.1: bytes=32 time<10ms TTL=32
Reply from 127.0.0.1: bytes=32 time<10ms TTL=32
Reply from 127.0.0.1: bytes=32 time<10ms TTL=32
Reply from 127.0.0.1: bytes=32 time=1ms TTL=32
PING statistics for 127.0.0.1:
Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milliseconds:
Minimum = 0ms, Maximum = 1ms, Average = 0ms
If you do not receive a successful PING from yourself, in Windows, try re-installing the TCP/IP protocol from the Network Control Panel or the Network Interface card drivers.
8. If PINGing your loopback worked fine, then try PINGing someone who is on the same subnet as your PC. Be sure the target IP address being PINGed is a valid IP address assigned to a system; otherwise, you'll receive errors. Use the Start | Run | IPCONFIG command to learn your NT/2000 machine's IP configuration (use WINIPCFG with Windows 9x).
WINDOWS SYSTEMS
* IP Config provides valuable information about what network you are on, as well as your gateway address.
Windows 2000
9. If you can PING someone on your local subnet, move on to the next step. If you can't, you're probably experiencing a Physical Layer failure. The usual suspects are bad cables or a NIC gone bad (they do that sometimes). With loopback, you were just testing the inner workings of the TCP/IP protocol stack; with PINGing on your local subnet you tested for failure on the failing machine. Try replacing the network card and using a new patch cable.
10. The next problem area is the gateway. Find the IP address of your gateway. You can find this in the IPCONFIG screen with NT systems (WINIPCFG for Windows 98).
11. If you don't have a gateway configured, then one will not show up in WINIPCFG, and this is a problem if you are connecting to another network. In Windows, locate Start | Settings | Control Panel | Network | TCP/IP | Gateway and add your gateway. This is your local interface on your router.
* PING this address; this will prove a solid connection from your PC to the gateway. If you have
made it this far, the PC is working, the cabling is working, and the router (gateway) interface is
working. You can skip to the next section.
* However, if you receive no response from the gateway, and you have one configured, it's time to
call the Network Administrator. Your router is improperly configured. It must have a local
interface (IP address) on your subnet to listen to the traffic on your network. If there is no
interface, have the router administrator add one. If it has one but has stopped working, it could
mean you're experiencing a router failure, and others will be affected as well. Conversely, the
router administrator may have loaded an old config; check with the administrator to make sure
this isn't the case.
12. The final step is through the gateway. PING something that is on the other side of the gateway. In an intranet, PING a printer on a remote subnet. On the Internet, PING Canon USA (128.11.96.121). If you do so successfully, you should not have a problem. If you can't get to a particular system in your network or on the Internet, that resource may not be available or the router's routing table may be misconfigured. |
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Originally Posted by ronex
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