It's not the WiFi, it's DHCP!
WiFi connectivity is as important as its wired counterpart for many organizations. As we have discussed in other occasions Wireless Networks are susceptible to many factors that cause wireless interference and the disruption of network services. Things such as channel interference from other WiFi networks, electromagnetic interference, physical obstacles, and other networking services not functioning properly such as DHCP and DNS can cause havoc on your wireless network. To the unsophisticated user it’s simple to put the blame on the WiFi network, after all you expect to connect to the network after entering the credentials but the reality is that in order for the Wireless Network to function properly all other components that make up the network must be working properly as well.
Today I want to address how a DHCP may affect the wireless connection in your company, the reason why I’m taking the time to go over this is because I’ve seen this exact problem on various occasion in different organizations in NYC, three times we’ve been able to troubleshoot the problem for businesses and one time for a school.
For starters let’s go over real quick how a Wireless Network works and the most common components in it, we’ll then evaluate how each component may affect Wireless communication in the event of its failure.
A Wireless Network is the “extension” of your physical network being broadcasted over the radio frequencies, of course that’s an explanation in its most simplest form but for many businesses it is the extent of it. The broadcast aspect is done by the Access Point’s antennas over the radio frequencies, be it the 2.4 GHz or the 5 GHz. The Access Point is connected to your physical network through an Ethernet port and from that point on it relies on other network services for its normal operation.
The first thing that happens when a WiFi client connects to the network is the WiFi authentication, this process is straight forward, if you have the right credentials you’re allowed to associate and if you don’t have them then you don’t associate the the WiFi network. For simple network environments associating to the WiFi network also means gaining network access to the network but that's not always the case.
Immediately after the association takes place the client request an IP address by broadcasting DHCP requests to the network - this is the behaviour for most environments but by no means is the only setup, you can have a WiFi network and configure all your devices with static IP address with no need for a DHCP server -. This DCHP service is where we’ll concentrate on this post, the function of DHCP is to distribute IP addresses to the requesting clients and the IP addresses in turn allow the routing services devices need to communicate in the network.
DHCP can be implemented from the Firewall or a Server such as Windows Server, the DHCP server has pool of addresses that are to be leased to requesting clients, the lease time configurable by the administrator depending on the capabilities of the DHCP server. A common problem we’ve noticed when companies call us to troubleshoot WiFi Network issues is that the problem is not really a WiFi issue but rather another network service like DHCP. After working with thousand of networks over many years this is one of the easiest problems for us to spot as it affects Wireless communication. The main sign that the problem is DHCP issue and not the WiFi is that clients can’t connect to the network, if you have a Mac you’ll see the WiFi icon’s bars going up and down as a sign of looking for a DHCP server.
If you more a techie you can fire up wireshark to find out what’s happening in the background, if you pay attention to the graph above you’ll notice how the client is sending DHCP discovery packets over the network, if the DHCP server does not respond the client will fail to connect to the network. To the naked eye this type of behavior is a reason to point the finger to the Wireless Network but it reality it has nothing to do with the radio signal.
A good simple troubleshoot technique to find out where the problem lies is by assigning valid IP settings to your WiFi interface, this type of troubleshooting makes more sense for administrators and average users may not know the network settings for the WiFi.
There are many reasons why a DHCP server would not work properly and we’ll address them in other post for now keep that when WiFi is acting it may not necessary mean that there’s network interference affecting the communication.
I really hope saved you a banging your head against the wall, we know the troubleshooting WiFi Network is challenging with the right knowledge and tools you can get to the root cause the any network issue. We're network expert, we have in-depth knowledge of or WiFi and Ethernet networks and most importantly how all network services work.
Feel free to contact us at 888-580-4450 if you assistance with your Wireless or Wired network configuration.
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