Windows Vista is no different than any other operating system in that, sooner or later, you will have networking issues.
#1: Use the Bottom Up Approach
Start your troubleshooting by checking for physical connectivity. Here are some questions to ask yourself:
- Is my network cable connected?
- Do I have a link light on the NIC?
- Does Windows see my NIC and see it as connected?
- Does the Ethernet switch have power and show a link light?
Whether you have a wired or wireless connection, the questions are the same (or similar). Take for example this Vista Wireless network connection status:
Figure 1: Vista Wireless Connection Status
You want to look at the “media state”. In this case, the media is wireless but the important thing is that it is enabled.
If you are attempting to connect to a wireless network, make sure that you are actually connected to a network. You can click on Connect to a Network to either connect or disconnect from a wireless or dialup network.
On a computer with a physical Ethernet connection, you are going to look for the same thing. Take for example this Windows 2008 Server with an Ethernet NIC:
Figure 2: Windows 2008 Media Stat
On this server, you can see that the Ethernet media on the wired LAN connection is enabled and you can see that the speed is 10.0 Gbps.
If you can verify these things, more on up the OSI model until you find the issue. The old network admin joke about the OSI model is that the non-existent 8th layer of the model is the “end user” and that they are many time the issue.
Many of these other things will fall into the category of testing various layers of the OSI model but, as with most networking tools, they apply to the testing of the Network & Transport layers which cover TCP/IP.
#2: IP Addressing
Let us say that you checked your media state and your link light and you have physical network connectivity. Moving on up the OSI model, we will skip the datalink layer (layer 2) as Ethernet MAC addressing is usually not an issue and move to IP addressing (layer 3).
At this point, you need to check your IP addressing in to ensure that:
- You have a real IP address (not an automatically assigned IP address)
- Your IP address is correct and matches your network & default gateway addresses
- You have default gateway and DNS Server IP addresses defined
To do this, open the Network and Sharing Center and assuming you have a connection, click on the View Status for your connected network interface.
Figure 3: Viewing the Status of your Connection
Then click on Details to see the IP address, subnet mask, default gateway, and DNS Servers. If you take a look at the details for the connection in Figure 4, notice that this connection has no default gateway or DNS servers.
Figure 4: Connection without a default gateway or DNS Servers
Lack of these will certainly prevent you from really using your network connection as normal. Of course, neither of these are required but most of us want to communicate outside of our local LAN. A default gateway is required for that. Also, most of us want to communicate with servers by name (such as using www.windowsnetworking.com instead of 220.127.116.11) and DNS Server IP’s are required for that.
Of course, you can also do an IPCONFIG /ALL to check all your IP settings, like this:
Figure 5: Results of IPCONFIG /ALL
Perhaps you did not receive these settings because your adaptor is not using DHCP.
Even if you do have a valid IP address, default gateway, and DNS Servers, you should ping these to ensure that you can really communicate with them.
#3: Windows Vista Diagnose and Repair
Fortunately for those who do not want to get into troubleshooting, Vista does offer the automatic Diagnose and Repair of network connections. Us IT Adminstrators can also use this as the “shotgun approach” to solving our problem quicker without getting into trying all sorts of things. To use diagnose and repair, just open the Network and Sharing Center and click on Diagnose and Repair.
Figure 6: Diagnose and Repair
Vista help also calls diagnose and repair “Network Diagnostics”. This tool will go through and check your network connection to identify problems. It will tell you basically what is wrong in the network connection but if you want more detailed information, you can check the Event Viewer.
#4: Network Filtering and Discovery
As we move on up the OSI model, we get into TCP layer and application layer filtering. Firewalls are used to filter inbound and outbound network connections. Firewalls could be local on your Vista computer or they could be out on the network, filtering inbound or outbound connections to/from the Internet. Of course if the firewall is out on our LAN that is beyond the scope of this article. As for firewalls on your local Vista computer, you can even have more than one but the first one (if you installed a 3rd party firewall). However, the first thing that you want to check is the Windows Vista Firewall that is installed and enabled by default.
It is unlikely that the Vista Firewall is blocking all network access. It is more likely that it is blocking just certain inbound or outbound network connections for specific applications. While it is risky on a public shared network to disable your firewall, one of the first things that I usually do when I get to this point is to just turn off the Vista Firewall to see if your problem is resolved. If it is, you can re-enable the Vista Firewall and then troubleshoot it to determine what port you need to allow your network traffic through.
To disable or add exceptions for the Windows Firewall, just click on Windows Firewall inside the Network and Sharing Center. At this point, you can view its status.
Figure 7: Checking the Windows Firewall
We can see that the Windows Firewall is enabled and that means that inbound connections that do not have an exception will be blocked. We can see that we should get a notification when a program is blocked.
To try disabling the firewall or creating an exception, click Change Settings and you will see this:
Figure 8: Changing Windows Firewall Settings
Here you can turn the firewall Off, view/modify exceptions with the Exceptions tab, or look at advanced features.
Besides the Windows Firewall, if you are having trouble accessing computers on your local network, you need to check your Network Discovery settings. To do this, go to Network and Sharing Center and scroll down to the Sharing and Discovery section. Check your settings for things like Network Discovery, File Sharing, and others.
Figure 9: Sharing and Discovery
#5: Use Common Sense Network Troubleshooting
While I have offered a number of technical troubleshooting tools, one of the things that more often than not is missed, is just using what I call “common sense” when it comes to troubleshooting network issues. Here are some common sense tips:
- Did you or someone else change something that could have caused this new networking issue?
- Are you even connected to the network?
- Are you assuming that all network connectivity is lost when really it is just one server or application that is not functioning? (its easy to test for this)
- Check one thing at a time then move on to the next. Do not change 3 things then see if it works or you will never know what resolved your issue (and you may even create more issues with the multiple changes). And if you change one thing that does not fix your issue, change that thing back to where it was before changing something else.