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Now, some of the other things that can go wrong, incorrect DHCP address range. For example, there's a default address range that most routers will hand out if they're configured to hand out DCHP addresses when they're installed or when they're right out of the box when they're installed from the factory. Now, frequently people change that but don't exactly make the changes correctly or they have static IPs on some of their clients so they're not even on the same IP address range. So you might find that they show a connection to the wireless access point, but their IP address range is wrong so they can't connect to the rest of the network. So make sure you look for DHCP address ranges, make sure they're in there correctly and hand out the proper address ranges. And make sure your clients are set to receive DHCP addresses versus being configured statically. Now, another problem you might see, and actually I've see this a couple of times, is MAC filtering turned on. Now, as we've talked about before, MAC filtering can be turned on to enable only certain computers with certain MAC addresses specified to access the network or to deny entry into the network to any MAC addresses not in the table. In any case, you can configure this table and accidentally leave out a client or exclude the client from the table and they can't connect. So that's something you want to look at if you use MAC filtering. Now, a wrong channel setting can cause interesting problems. Now, this does not frequently happen and the reason it doesn't is most people don't mess with the channel settings on their wireless access points. Standard channels in the US, one, six and 11 that most wireless access points are configured for by default are usually just fine. But occasionally some administrator, you know, when they're messing around with the wireless access point, may set the channel inadvertently to a different channel or maybe set on the card inadvertently in the wireless access point. So if you've checked everything else and all else should be working and you can't think of a reason why it's not working, maybe look at the channel settings. Now, on a side note, when you have a large concentration of wireless devices that use the same channel, you might look at changing the channel setting for your access point and all your clients so you don't get all that interference. Some other settings you might need to look at are WAN settings. Now, if you work in a small office environment or a home environment and you WAN side of the wireless router that's wired, that maybe runs into a DSL connection or dedicated T1 connection or cable modem, if that's set incorrectly, then all of the clients can talk to the wireless router but they may not be able to talk to the Internet. So you may have to go back and look at some of those WAN settings and that may, in fact, require coordination with your ISP or your provider. Another problem that can happen is range. Just sometimes it, especially if you have multiple access points, you may not position those in the right places, so certain clients may not have a good range and can get to those wireless access points. In those cases you might think about adding a wireless access point and putting it in ESS mode or infrastructure mode so the other devices can access it or you may have to move those wireless clients a little bit closer to that wireless access point. But if they're having weak or intermittent connection, range is usually the problem. Also, frequently you can see too many wireless devices co-located, which cause interference. I think I mentioned this before, but you might want to consider changing the channels if you're in a heavily populated area and maybe you've not only got your wireless access point to contend with and your wireless network, but multiple wireless networks from other businesses or home or things. You might consider changing the channel. Sometimes that helps because too many devices using the same channels can cause interference problems and they can cause confusion among your users and your administrators when you're trying to sort out which access point belongs to you and which doesn't and you're trying to configure encryption and things of that nature, especially if every access point, uh, that's sitting around you has the default SSID of Linksys. So you might consider changing some of those settings. Now, I can't emphasize this enough. Once you have a working configuration and everything works the way you need it to, your encryption is set correctly, you DHCP scope is set correctly and everything else is working, back the configuration up. That way, if something goes wrong, you can restore that configuration. Most wireless access points have the ability to backup configuration into a text file or some other file and then if something happens and the access point losses its configuration, you can go back in later and upload that backup configuration and restore it fairly easily and that way you don't have to recreate it from scratch and risk messing something up. And again, document all changes to your infrastructure. If you're going to make a change on a wireless access point that could potentially affect other access points or clients, document that change and then test it so that you know if there are problems out there and that way if a client comes up later and can't connect, you can go back to your change log and see what was the last thing that was done to the network. So you can kind of get an idea where you need to start troubleshooting. Now, these troubleshooting points aren't necessarily all inclusive and they don't cover every problem you could have, but these are some of the more popular things out there that you should look for when you have connection problems between your wireless access points and your clients.