All important info about the Dynamic Host Configuration Protocol
You may have heard of the Dynamic Host Configuration Protocol, better known as DHCP. In computer networks it belongs to one of the basic protocols. It is responsible for the automatic IP address management from a server to one or more clients.
To understand the working principle of DHCP, you should first ask yourself some basic questions. How is a computer recognized in a network like the Internet? How do you identify where data is sent to and what belongs to the Internet and what belongs to your home network?
Responsible for this are, among others, the IP address, subnet mask, DNS server and other addresses that are automatically assigned by DHCP. Manual setups are then no longer necessary.
What exactly does DHCP manage?
DHCP assigns the following addresses and address information:
IP address, the address of a device on the network
Subnet mask, addressing of the network and host part of an IP address
Default gateway, the bridge from one network to another
Primary and secondary DNS server, the server that holds a list of IP addresses and their human-rememberable names and resolves them accordingly
Time and NTP servers, which are responsible for synchronizing the time of day
In addition, there are many other things like WINS servers and proxy configurations that can be managed by DHCP.
What is a DHCP server and what is a DHCP client?
In a network, one device must always be the DHCP server that assigns addresses to all (DHCP) clients. While there are often separate DHCP servers in companies and in large communication networks, in your home network a router is used in practically all cases, which assigns the IP addresses and also serves as a gateway and DNS server. It is therefore the central administrator for all data transport between your home network and the Internet, as well as between the devices in your home network.
What exactly is DHCP needed for?
Without IP addresses nothing works in the home network. If a device makes a request to another device without an IP address, the device does not know where to send the response. The result would be an enormous load that would cause a network to collapse. DNS is used, for example, to convert an address that is memorable to you, such as google.com, into an IP address that can be used by computer networks.
In the past, a hosts file was used for this, which still exists in Windows today. For example, if you didn't have a current IP address for google.de in the file and tried to access it without a DNS server, you would only get an error message.
The first DNS server is your router. It knows up to two DNS servers of your Internet provider to which requests are redirected. These two DNS servers are also assigned to your router via DHCP. Without the automatic assignment you would not know which are the current DNS servers. And even if you knew, the setup is extremely complex. The same goes for the other IP addresses and the subnet mask.
How to enable or disable DHCP?
If your DHCP is not working, it can basically be due to two different reasons. Either the DHCP server or the DHCP client is not working. The exclusion principle is the best way to find out the reason. If only one device in your home network doesn't get IP addresses, the client on the PC is usually to blame, while if all devices don't work, it's usually the server.
You can restart or start the DHCP client in the Windows services. To do this, proceed as follows:
Press the Windows key together with "R".
Type "services.msc" and confirm your input with the "OK" key.
Click with the right mouse button on the "DHCP client" and select "Start" or "Restart".
The process will take a few seconds and a new DHCP request will take place. You can disable DHCP in the same way. However, you would then have to assign the IP addresses on your device yourself in order to access the home network and the Internet.
To enable or disable the DHCP server on a Fritz!Box, proceed as follows:
open your Fritz!Box user interface by typing fritz.box or 192.168.178.1 into the address bar of your internet browser
if a password was assigned, you have to enter it now
click on "Home Network" and then on "Home Network Overview
select the tab "Network Settings
here you can now enable or disable the DHCP server
The setting is only available in the advanced view. You can activate it by clicking on the three dots in the upper right corner of Fritz!OS version 6.50 or higher and moving the slider to the right. For older firmware versions, you will find the settings at the bottom center. Here it is sufficient to simply click on the term "Standard".
On older models, the names in the menu may be slightly different.
Error message "No valid IP configuration" - what to do now?
If you don't have access to the Internet anymore, you might quickly get to this error message. It means that an error occurred during the DHCP address assignment, for example because no IP addresses could be assigned. This is often recognizable with Windows operating systems by the IP address 169.254.x.x, which was assigned by Windows itself because a valid configuration is missing. A few steps are often sufficient to eliminate the error.
Starting with Windows 7, the operating system can make some corrections on its own, such as restarting the network adapter, which can solve the problem. To do this, proceed as follows:
Press the Windows key together with "R".
Type "ncpa.cpl" and confirm with "OK".
Right-click on the network connection and select "Repair" or "Diagnose
Follow the instructions on the screen
If this does not help, it may be necessary to assign IP addresses manually. This is how to do it:
Right-click on the network connection
Check "Internet Protocol Version 4 (TCP/IPv4)" (the IPv6 protocol is not yet fully usable)
Mark the post and select "Properties
Go to "Use the following IP address
The IP addresses for a Fritz!Box with a standard setup are as follows:
IP address: 192.168.178.x, where x must be outside the DHCP range and between 2 and 255
Subnet mask: 255.255.255.0
Subnet mask, primary DNS server: 192.168.178.1
The Google DNS server (8.8.8.8) can be used as the secondary DNS server. The entry can remain free.
