Configuring Network Connectivity in Visual Studio .NET

Printer Code 39 in Visual Studio .NET Configuring Network Connectivity

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Ian McLean I recently came across the problem of a statically configured computer in my own home network, although the situation was a bit different. The computer that was connected directly to the Internet and providing ICS was experiencing memory problems. I had a newer and more powerful computer that I wanted to use for this purpose anyway so I replaced the old computer. I then bought some RAM, installed it on the old computer, and decided I might as well plug it into a spare port and use it as an ordinary workstation. Did I remember to reconfigure the interface so the computer obtained its TCP/IP settings dynamically Well, put it this way it wasn t just the computer that had memory problems. If you can successfully ping your computer by name and IPv4 address and are happy with the results obtained by ipconfig, you can then try pinging other workstations on your network by IPv4 address and computer name. Finally, you should check that you can ping your default gateway from all the computers in your network. You can then test connectivity to your ISP by pinging the ISP s DNS server.

In general, if ipconfig /all identifies a default gateway and an internal and external DNS server, the computer is likely to be able to connect to them. However, IP configuration is refreshed periodically and it is possible that connectivity has been lost after the last refresh. It is worthwhile pinging the default gateway and DNS servers to check this out.

If you cannot ping a computer on your network to test connectivity, make sure your internal firewalls are not blocking ICMP. (On a computer running Windows Vista, Windows Firewall permits ICMP by default.) If the problem still exists with the firewalls reconfigured or disabled (please remember to enable them afterward), check the physical network connections again (you should have done this first) and use ipconfig on the computer you cannot reach to check its IP settings.

You have purchased a second-hand computer and are connecting it to a hybrid network that obtains its configuration from DHCP provided by a third-party WAP. The computer is not wireless-enabled, so you plug it into an Ethernet hub and switch it on. It cannot access the Internet. You enter ipconfig from the Command Prompt console and discover that the computer has an IP address of 10.1.10.231. You know the WAP is working properly and the Ethernet connection is okay. What should you check next

Quick Check Answer Check that the computer is set to receive its TCP/IP configuration dynamically. It has not been reconfigured by DHCP on the WAP and its previous owner has probably configured it statically with the 10.1.10.231 address. You need to reconfigure the computer to receive its TCP/IP settings dynamically. If you want to reconfigure IP settings on a workstation on your network, you can reboot it. If this is not convenient, the commands ipconfig /release and ipconfig /renew release the old configuration and obtain a new one. (In theory, ipconfig /renew should be sufficient, but I always use both commands.) Sometimes when you renew a computer s configuration, it does not immediately register its new settings in DNS and you cannot ping it by computer name. In this case, ipconfig /registerdns forces registration.

The ipconfig /registerdns and ipconfig /flushdns commands require that you run the Command Prompt Console as an administrator. To do this, select Accessories from the All Programs menu, right-click Command Prompt, and click Run As Administrator. As with all administrator level prompts, the UAC dialog box will, by default, prompt you to provide administrator credentials or click Continue.

If you try to ping a computer by name or access a website from a workstation and DNS cannot resolve the computer name or URL, then information that resolution has failed is stored (cached) in the workstation. If you try to do the same thing again, the workstation will not attempt to obtain name resolution but will instead use the cached information and again fail the request. This is known as negative caching. However, name resolution might have failed because of a temporary glitch in the internal or external DNS service. Even though DNS is now working, the computer name or FQDN will not be resolved to an IPv4 address because of the cached information. The problem will disappear in 30 minutes or so because the workstation s DNS resolver cache is regularly cleared. However, if you do not want to wait this long, you can solve the problem immediately by using the ipconfig /flushdns command to flush the DNS cache.