If you check your computers IP address and it shows an IP address starting with 169.254.xxx.xxx more than likely what ever device or computer that acts as a DHCP server has an issue.
Some symptoms you might notice besides the strange IP address are:
- You can access shared files on other computers but not other network resources
- You can’t access the internet
So how do you fix it?
This depends on your network setup but the most basic and simple initial step is to reboot the device that provides DHCP. This may be a router or could be a windows server, if you’re unsure of which device provides DHCP you should contact your IT department or external provider for assistance.
Once you’ve done this step you can disable then re-enable your network device and see if you get a new IP address. If your address no longer starts with 169.254.xxx.xxx your DHCP server is now working again – however you should probably investigate further in to why it failed in the first place.
If you’ve rebooted your DHCP device and you are still having issues the next step would be to set your computer to have an IP address that is in the same range as the rest of your equipment manually. For example if you know your main internet routers IP address is 192.168.1.1 and has a subnet of 255.255.255.0 then set your computers address to be 192.168.1.74/255.255.255.0 and gateway 192.168.1.1 – If you get a message saying that there is an IP address conflict change the last set of digits on 192.168.1.74 to something different (anything between .2-.254).
Once you’ve manually set your address try and ping different devices on your network – if you can ping your devices that’s a good sign, more than likely its just your DHCP server thats failed and not your network equipment. If you can’t, well then you need to start looking at your network infrastructure overall because its got bigger issues!
If you were able to ping everything you then need to connect in to your device that does DHCP and check – is DHCP even enabled?
Enabling/Re-Enabling DHCP Servers
On a standard internet router there is normally a section that says use router as DHCP server. Check that it is on and make sure that the DHCP range that is configured matches your network and has enough IP addresses available to allocate to all of your devices. Most routers will require rebooting for the change to take effect.
If you are using a windows server you can check services.msc and ensure that DHCP Server has started, if it has not – right click on the service and go to “Start” hopefully it will start normally, then you can check that it is set to automatically start so that you don’t have to fix the issue again. If there is a problem you normally we see an error and can investigate further.
If you are using linux it depends on what DHCP server software you are running – I normally use isc-dhcp-server and raspbian on a Raspberry Pi. To restart that server type the following:
sudo service isc-dhcp-server restart
Again, if there are errors they should display but if there is not the service should start with no issues.
Once you’ve managed to get your DHCP server up and running again all you should need to do is re-configure your network adaptor to obtain an IP address automatically – and you should be able to get your normal DHCP assigned IP address and will be able to access your network devices and the internet again.
Why use DHCP in the first place?
DHCP allows you to allocate IP addresses automatically and you can configure the addresses, gateways and DNS servers that each device will be given – and that’s on the most basic level, DHCP has more abilities that are helpful in network environments (for example google DHCP Option 66) Without DHCP you would need to manually set every single devices IP address – and – if you ever have a network change you’d have to reconfigure all of your devices manually for things to be able to “talk” (network) again. Would you really want to do that on a network of say 100 computers? I certainly wouldn’t.
I am often surprised to find some offices and point of sale setups where another provider has not even bothered to set up DHCP. The excuses that are given by some people I find even more surprising – my favourite I hear all the time is “But I don’t want the addresses to change” – there are very few circumstances where this is a valid argument in those environments. It’s important to remember that even if you are using DHCP you can still use “address reservation” which will ensure that certain devices always receive the same IP address.
How does that differ from a static address?
If you set up DHCP to use address reservation and you had to replace your DHCP server or device that provides a DHCP server you’ll get a new IP address (unless of course you actually copy the configuration from your old server as well then address reservation would be enabled right?) – whereas with a static IP address it never changes at all unless you manually reconfigure it to something else.
If you’re setting up a network strongly consider whether a static IP address is actually required. Generally there are only a few devices that should have static IP addresses and they are not your standard office computers.
Why I configure networks using DHCP
The reason I always use DHCP is if one of our customers purchased a new modem, or their ISP sends them a new one because the old one is broken and they attempt to set it up themselves the computers should ask for an IP address from the DHCP server from the new router – no equipment needs reconfiguration.
In larger office environments it also allows for greater control over exactly what network addresses and other settings you want client computers to use and is manageable from a single point.
I’m still having trouble can you help?
If you are still having issues with your networking setup feel free to contact us