Diagnosing and Fixing DNS Problems

DNS is used on TCP/IP-connected networks to convert computer names to IP addresses. For example, you can type in www.microsoft.com, and DNS converts that to an IP address. DNS exists because it is much easier for humans to remember a name than a cryptic number. However, DNS creates a layer of abstraction over the information that is required for connections to successfully complete. Any time you take a step away from a very simple system, there is the opportunity for error, and DNS is no exception. The following are two of the things to check when trying to diagnose potential DNS issues:

• Check to make sure you have the correct DNS Servers configured in your TCP/IP settings You should check the detailed settings for your TCP/IP configuration to ensure that you have the DNS servers that are recommended by your ISP.

• Check with your ISP to make sure it is not having problems It is worth taking the time to call your ISP's tech support line to find out whether the ISP is experiencing any problems that might be affecting your network. Many ISPs have web pages you can visit to check on current network status, and doing this can save you time and effort when troubleshooting.

• Check your VPN settings If you connect to a VPN at your office, you may lose the ability to connect to the Internet. As discussed in Chapter 5, "Project 4: Instant Messaging in and out of Your Home Network," in the sidebar "Windows Messenger on a VPN," what ends up happening is that when you make a VPN connection, your computer has routing reconfigured to send all traffic through your corporate network, which may or may not offer the ability to send your request back to the Internet. You can follow the steps outlined in the sidebar in Chapter 5 to resolve this issue.

  The Browser Service

  The browser service is a rather complicated service that causes a list of available networked computers to appear on your screen. In general, you should not have to wait any longer than 24 minutes for resources to appear, and in small networks you should most likely not wait more than 12 minutes. If you end up waiting longer, something serious may be going on. For a detailed discussion of the browser service, see Microsoft Knowledge Base article 188001, which is available at http://support.microsoft.com/default.aspx?scid=kb;en-us;188001.

  
  

• Clear your DNS cache You can resolve any temporary DNS problems by running ipconfig /flushdns from a command prompt. This has the effect of clearing your DNS cache and forcing your computer to obtain name resolution all over.