Troubleshooting Windows 7 Wireless Networking Problems (Part 4)

by [Published on 7 Oct. 2010 / Last Updated on 7 Oct. 2010]

This article concludes the series on Windows 7 wireless networking problems by examining issues related to hidden network errors and incorrect DHCP settings.

If you would like to read the first article in this series please go to

Introduction

Throughout this article series, I have discussed various factors that can potentially cause wireless network connectivity to fail with Windows 7. In this article, I want to conclude the series by talking about a few other miscellaneous wireless networking problems that I have run into.

Hidden Networks

Another wireless networking related problem that I have run into from time to time involves the user receiving a message stating that the network is marked as hidden. This particular error message also occurs in Windows Vista.

I have read countless posts on the Internet from people who swear that this particular error is due to a bug in Windows. Although I cannot definitively say for sure whether or not this error message is related to a Windows bug, I tend to think that it probably is. I say that because I have seen the error occur even in situations in which the wireless network is not hidden.

Thankfully, there are some workarounds for this problem. First, make sure that the wireless access point that you are trying to connect to is broadcasting its SSID. If the SSID is being broadcast, then the network is not hidden, and the error message is definitely false.

Another thing that you can do is to make sure that the access point is not performing any sort of filtering on MAC addresses. Personally, I have never seen this particular error occur as a result of MAC address filtering, but there are those who claim to have been able to resolve the error by disabling MAC filtering on their access points.

The last step – and this is the big one – is to configure your access point to use WPA-PSK encryption. While I was researching the Network is Marked as Hidden error, I noticed a common thread. Most of the people who were receiving the error were using WEP encryption. This led me to do some research to see if there were any issues with WEP, and indeed a number of people claim to have resolved this issue by switching from WEP encryption to WPA encryption using a pre-shared key.

DHCP Configuration Problems

Another common cause of wireless networking problems involves incorrectly configured DHCP settings. Most of the wireless access points that are available include a built-in DHCP server. If the built-in DHCP server is misconfigured, then numerous problems can occur.

One of the biggest problems that I have seen regarding DHCP configuration revolves around the DNS settings. On my own network for example, I have a wireless access point that also acts as an Internet gateway. Unfortunately, the manufacturer (who shall remain nameless) decided to try to design the access point in a way that would make the configuration process idiot proof for home users. One way that the manufacturer tried to make the configuration process easier was by omitting the DNS settings from the DHCP configuration. Instead, the device automatically provides users with the address of the ISP’s DNS servers.

While this may not sound like such a bad thing, it can be very problematic for those who are operating Windows domains. The Active Directory is completely dependent upon the DNS services. As such, network clients must be configured to use an in house DNS server rather than a generic DNS server that has been provided by the ISP. The in house DNS server resolves queries related to the local network, but also uses either root hints or forwarders to resolve queries for Internet domains.

My point is that if you are using an access point like this one that automatically assigns DNS addresses to clients then it can cause problems. The client computers shouldn’t have any trouble connecting to the wireless network, but once connected users may find that they have trouble accessing certain network resources because their computer is using an incorrect DNS server.

The way that I was able to resolve this issue on my own network was to use a mixture of static and dynamic IP address configurations. If you look at Figure A, you will notice that Windows is designed so that you can use a dynamic IP address that has been assigned by a DHCP server, while using a static DNS server assignment. I simply took advantage of this fact by manually entering the addresses of my DNS servers while allowing the access point’s DHCP server to assign an IP address to the client.


Figure A: It is possible to use a static DNS server assignment while using a dynamic IP address assignment

Another issue that seems to trip up a lot of people is the DHCP scope. The DHCP scope is the range of IP addresses that a DHCP server can assign to network clients. Most of the wireless access points that I have seen are preconfigured to assign addresses from a certain scope (usually 192.168.0.x).

The problem with this is that the preassigned scope may not mesh well with your network. For example, I use IP addresses in the 147.100.x.x range on my own network. If I allowed my DHCP server to assign addresses in the 192.168.0.x range then wireless clients would probably be able to access the Internet, but they would not be able to access any of the resources on my private network. This is because all of the network devices that share a common network segment are expected to use a common IP address range.

A similar problem involves overlapping scopes. On my own network for example, I configured my access point to assign addresses from the 147.100.x.x range, as opposed to the factory assigned 192.168.0.x range. That way, the address range fits in with the rest of my network. That alone wasn’t enough however.

I have quite a few servers on my network that use static IP addresses. I also have a DHCP server on my wired network that hands out IP addresses within the 147.100.x.x range. If I allowed my access point to blindly distribute addresses in the 147.100.x.x range then there is a good change that the access point would assign an address that was already in use elsewhere on my network. Some DHCP servers will check to see if an address is in use before assigning the address to a client, but you can’t always depend on that functionality. It is better to prevent IP address conflicts from ever having any chance of occurring.

I have resolved this issue on my own network by reserving different scopes for different purposes. I reserve the 147.100.100.1 to 147.100.100.100 block of addresses for servers that require a static IP address. The block of addresses ranging from 147.100.100.101 to 147.100.100.119 are assigned by a DHCP server on my wired network, while the 147.100.100.120 to 147.100.100.200 block of addresses are assigned by my wireless access point.

Conclusion

As you can see, there are numerous issues that can prevent wireless networks from functioning correctly in a Windows 7 environment. Thankfully, it seems as though there are workarounds for the most common problems.

If you would like to read the first article in this series please go to

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