Troubleshooting Internet connection problems can be a challenge because there are so many possible causes. First, try these steps:
Open Network Diagnostics by right-clicking the network icon in the notification area, and then clicking Diagnose and repair.
Make sure that all wires are connected (for example, make sure your modem is connected to a working phone jack or cable connection, either directly or through a router).
Reset your modem and router. Remove the power cord from the modem and/or router, wait at least 10 seconds, and then plug the modem and/or router back in.
Check your router. Because of the new networking features in Windows Vista, some older network routers are not fully compatible with Windows Vista and can cause problems.
If these steps don't solve the problem, look for a specific problem in the following list.
Make sure that:
Your modem is turned on.
The Ethernet cable is plugged correctly into the Ethernet port on the modem and on your computer. Each end of an Ethernet cable looks like this:
The phone line is plugged correctly into the modem and the phone jack.
You are not using a DSL filter between the phone jack and the modem.
Check the lights on your modem. These can sometimes indicate the location of the problem—whether it is the Ethernet connection, the power to the modem, or the DSL or cable connection.
Winsock corruption can cause connectivity problems. To fix this, open Network Diagnostics:
For more information, go to How to determine and recover from Winsock2 corruption on the Microsoft website.
Ask your Internet service provider (ISP) to verify that:
Its servers are functioning correctly.
You have an ISP user account and access to the ISP service.
Make sure that you are dialing the correct number, including any required access numbers (such as 9), and that the number is not busy.
Make sure that the phone jack is working. To test this, plug in a working phone and see if there is a dial tone.
Make sure that the phone cable is plugged into the "line" jack on your modem, not the "telephone" jack.
Make sure that the phone cable is not defective by plugging a working phone into the "telephone" jack of your modem. If there is a dial tone, the phone cable is working.
If you have call waiting, try disabling it, and then try the connection again.
Your ISP might have disconnected you if you weren't interacting with the website for a while. Try connecting again.
If someone picked up the phone while you were online, you might have been automatically disconnected. Try connecting again.
Most dial-up modems work only with analog phone lines. Verify that you have analog phone lines installed, or, if you have digital phone lines installed, verify that your computer has a digital modem.
Make sure that your modem is working properly. For more information, check the information that came with your modem or go to the manufacturer's website.
Contact your telephone company to verify the quality of your line.
If your computer has two network connections, the networking software must choose which connection to use for network traffic. The networking software picks the connection with the best performance. If connection A has Internet connectivity but slow performance and connection B has no Internet connectivity but better local network performance, the networking software will route network traffic over connection B. This means that you won't be able to view websites, so the networking icon and the network diagram in Network and Sharing Center will report that you only have local connectivity (no Internet). This is correct, but it's not what you want. To force your computer to use connection A—the connection with Internet connectivity—disconnect connection B and try again.
Here are some possible causes of this problem:
Your browser could be attempting to connect through a proxy server. If so, try connecting with the proxy server turned off. For more information, see Change proxy settings in Internet Explorer.
Your browser connection settings could be incorrect. For more information, see Internet Explorer Connections settings: recommended links.
Your router could be attempting to proxy DNS requests and failing. Refer to the documentation that came with your router for instructions on disabling DNS proxying.
A number of factors can affect Internet connection speed. For more information, see Why is my Internet connection so slow?
Make sure that you typed the virtual private network (VPN) server name exactly as provided by your network administrator.
You must have an active Internet connection for a VPN connection to work.
If your modem is external, make sure that the modem power is turned on.
Contact your network administrator to make sure that you have the appropriate connection and domain permissions on the remote access server.
This could be a certificate problem. For assistance, contact your network administrator.
A VPN connection won't work with an active Winsock proxy client. Contact your network administrator to make sure the Winsock proxy client is not enabled.
If you know the IP address (for example: 126.96.36.199) of a website, type that address in the address bar of your web browser and press ENTER. If this works, there is probably a Domain Name System (DNS) resolution problem. For assistance, contact your network administrator.
If you have special software that is required or installed by your workplace, it could be part of the problem. For assistance, contact your network administrator.
If you know the IP address (for example: 188.8.131.52) of your VPN server, type that address for the VPN connection, and then press ENTER. If this works, there is probably a DNS resolution problem. For assistance, contact your network administrator.
There could be a problem with the server you are trying to connect to. For assistance, contact your network administrator.
This can happen when the encryption that your computer uses does not match the encryption used by the VPN server. To change the encryption settings so that your computer uses the recommended setting of 3DES, follow these steps:
Open Network and Sharing Center by clicking the Start button , clicking Control Panel, clicking Network and Internet, and then clicking Network and Sharing Center.
Click Connect to a network.
Right-click the VPN connection, and then click Properties.
Click the Security tab, click Advanced (custom settings), and then click Settings.
In the Advanced Security Settings dialog box, under Data encryption, select Maximum strength encryption (disconnect if server declines), and then click OK twice.
Click Connect to try connecting again.