It’s difficult to troubleshooting something you can’t see. In this video, you’ll learn how to resolve wireless interference, manage channel usage, resolve roaming misconfigurations, and more.
On a wireless network, there are only so many frequencies available to be used by your access point and your clients. And you have to make sure on that wireless network that only one device is communicating at a time. Not only do we have a lot of devices on the same wireless network, we may have multiple wireless networks within the same general area. And because of that, we have to be very careful about creating interference between these access points.
Many of the more recent wireless standards provide a way to automatically find the best possible frequencies and avoid frequencies that are already in use by other devices. This can also be configured manually, where you can decide what frequencies to use. But most access points are very good at determining what the best frequency might be for the environment, and they’re able to change their configuration and move to a better frequency if they happen to detect interference.
We’ve shown this diagram in a previous video, but it’s worth mentioning, especially when we’re talking about finding a frequency that may be available and moving an access point to that frequency. If you’re using 2.4 gigahertz, you have a limited number of non-overlapping frequencies that can be used. In North America, there are three separate channels that could be selected. And if you’re in a very busy area with many different access points, that may not be enough to prevent any type of interference.
Instead, you might want to use 5 gigahertz. With 5 gigahertz, there are many other frequencies available, so you might have a better chance of finding one that doesn’t have quite as much interference. And now, of course, the 6 gigahertz band is available. And you can see there are many more frequencies available in the hopes that we can avoid these types of conflicts and interference with our frequencies in the future.
There are some best practices for managing a wireless network and getting the best throughput possible from your wireless devices. One of these would be to disable any legacy or low speed support. If you look at the configuration of your access point, it may have an option to allow older versions of wireless technologies to work on the existing network. In many cases, enabling those configurations will slow down or make the overall wireless network less efficient. The best possible throughput is often available from the most recent standards. So if all of your devices support the most recent standard, you should disable that option in your access point.
If you have manually configured a channel of frequencies in your access point, you may need to go back and make sure that this isn’t conflicting with anything else that may have appeared in the meantime. It’s very easy for someone to turn on an access point next door that could potentially conflict with the frequencies that you’re using. You might also want to consider turning on the automatic function so that your access point can move to a more appropriate channel when available.
Interference is one of the biggest problems you’ll find on a wireless network, and interference can come from many different sources. But often, the interference is from other access points themselves. Some access points may be covering a very small area, but their output power may be set to maximum. In those cases, you may be able to turn down the output power and still provide wireless access to those devices in the area. And by doing that, you’re limiting the interference that may be created for other access points in the area. And it’s not unusual to split the wireless network into smaller devices that are separated into access points that are away from each other. This way, you can still provide wireless access for these devices, but you’ve now limited that load across two different access points using different frequencies.
Here’s an example of the problem you might find on a network when these frequencies begin to overlap. We’ve taken, for example, this 2.4 gigahertz network. You can see that it has a channel centered on channel 6 and another one on channel 11. That is exactly what we would expect to see here in the United States. There’s one other channel available that would allow you to connect without conflicting with either of these existing networks, and that would be channel 1.
But if somebody’s configured their access point in the wrong way, they could configure channel 8. And that channel 8 would overlap with devices that are communicating on channel 6 and devices that are communicating on channel 11. In this scenario, none of these devices would have the best throughput. It would have probably been a better idea to put the new access point over on channel 1 and distribute those frequencies so that they don’t interfere with each other.
As you’ve probably seen with wireless networks, the farther away you move away from the access point, the weaker the signal tends to be. We refer to this as attenuation, and this is a normal part of sending signals out over the air. Many administrators will measure this attenuation with their Wi-Fi analyzer, so they will walk around the facility to find out where the signal is the best and where the signal is the worst. And they may be able to make changes to the access point to improve those signals in places where it may be difficult to access the network.
One of those options might be to increase the power output on the access point itself. Not all access points support this feature, but if it is available, you may be able to find exactly the right amount of power to cover the area that you need. You might also consider adding an external antenna to the access point or adding an antenna that provides additional gain. This would allow you to send the same amount of power out of the access point, but increase its ability to transmit over a larger distance.
And if you’re using antennas that are connected to the access point with coax, you do lose a bit of signal in the coax itself, especially when you’re using higher frequencies. So you may want to limit the amount of cable that is run between the access point and the antenna itself. And you should always check the cable and make sure that it’s not damaged where it could potentially be leaking signal instead of sending that out your antenna.
Finding the right coverage for a wireless network can sometimes be a challenge. It’s important to identify where users may be accessing the wireless network, and then you can measure just how much wireless signal may be available at that location. If you’re in an area with many different organizations and companies, you might want to see where their access points may be located. And that way, you know where to put your access points so that you’re not creating interference with others that may be in the area.
This might also be a good time to see what frequencies they are using. Perhaps they’re only using 2.4 gigahertz and 5 gigahertz, which would open up the entire 6 gigahertz range for you. But of course, what we examine today will probably be different in the future. There’s always changes and additions being made to people’s networks, so it’s sometimes useful to perform multiple site surveys throughout the year just to see if anything may have changed with the wireless infrastructure.
One of the ways that you can visually see how the wireless network may be working is to create a heat map. You would walk around with your Wi-Fi analyzer, and it would examine just how good the signal is at your particular location. The better the signal, the brighter the colors, and the worse the signal, the cooler the colors. This way, you can immediately see where you may want to add or change the way your access points may be distributed.
On older networks, you may run into a denial of service that could be created through a client disassociation. This takes advantage of older management frames in the 802.11 standard that have no protection associated with them. And an attacker can take advantage of that to remove devices from the network.
You may find that a device is constantly removing itself from the network and then reconnecting again. Or you may find that it’s never able to connect to a network because this attacker is constantly performing this client disassociation. If you’re wondering if this is happening on your wireless network, you can capture frames using an 802.11 packet capture device and be able to see the client disassociation frames within the traffic itself. This will allow you to find the attacking device and hopefully be able to remove it from the network or disable it. And if you’d like to prevent these kinds of attacks in the future, you should consider upgrading to one of the latest 802.11 standards, which prevent this type of attack from occurring.
If you have a number of different access points at work or at home, you may have configured those access points exactly the same with the same wireless network name, or the same SSID. That service set identifier allows us to create a large wireless network using multiple access points. And as you move inside of a building or throughout a campus, your device will seamlessly move from access point to access point. This allows the network administrator to extend this wireless network to whatever size they might need. But it also requires that all of these access points are configured exactly the same.
If users are moving from one access point to another and the new access point does not have exactly the same configuration as the previous access point, they could be dropped completely from the network and they would be required to connect to the network again. If you want that seamless experience for your users, you need to make sure that all of your access points are configured exactly the same with their security features and other configuration details.