What is an IP address conflict?
And so let’s imagine that in your organization, two people have completely identical full names. You ask a question at a meeting, “Who is madankc here?” and then two people come up to you. Here in the local network, two computers with the same addresses also appear. This is the situation in which a conflict of IP addresses is detected. It will be good if these are two client computers; the problem will be minimal. But what will happen if one of the participants is a server that performs an important function in the organization, for example, a 1C server? Believe me, they will not pat you on the head for this.
Windows IP Address Conflict Causes
Above, I showed you what the situation is with the same IP addresses in the Windows operating system. Let me tell you about the reasons for its appearance:
- The first reason is that when you have a local network, all network addresses on computers are assigned manually ( static IP addresses ). Typically, such settings are made for servers so that they always have the same parameters, but this method has a vulnerability. It is the need to maintain a register of these addresses in different forms and always update them. Otherwise, you may have problems with duplicate addresses. I often saw this in small offices, where there is a so-called administrator who does this, and then a new computer or laptop comes in, and an IP address is also driven in for it. As a result, a conflict of IP addresses was found on the local network. As they say, you have to pay for errors .
- The second option is when you have problems with the DHCP server, on which you either do not have the duplicate address tracking function configured, or your DHCP server assigned an IP to someone, and someone else took it and set up a static one for themselves. That’s what happened with the ip address conflict error. From my practice, I saw such a tent when one admin had Kerio Control , which had a DHCP server function, where addresses were assigned with a large reservation and sometimes tied. On one of the beautiful days in Moscow, a situation happened where the Internet stopped working for some people. This admin, instead of going to the DHCP server and seeing that he had run out of addresses in the pool, began to massively reboot computers and assign static IP addresses to them. As a result, he created a huge number of IP conflicts in the network. He simply did not understand the principle of the service.
I have already written so much about the reasons, but I still haven’t shown what the error message looks like.
If you go into the network interface settings, you will find that in this situation, your main address will be an IP from the APIPA range (169.254.xx). This means that the conflicting address will not be available to you, and you will not be able to communicate with almost anyone on the local network.
Also, if you look at the logs of the Windows operating system , you will find such a notification there: event code 4199:
Because of this, you may have a conflict of Windows Ip addresses. I told you, now let’s move on to the algorithm for solving this situation.
How to fix an IP address conflict?
Let’s take a look at what options there are to avoid the situation with the intersection or duplication of addresses on your computers on the local network.
- Firstly, if you have an ordinary small office and, for some reason, all local addresses are assigned exclusively manually, then be sure to keep a register of issued addresses, and you need to approach this issue responsibly. In the server segment, static is welcome. As one of the check handicaps, use the DNS server in the zone in which your computers and servers are registered. For maintaining tables, by the way, there is a convenient software product called rack tables. It is absolutely free.
In this case, to remove the Windows IP address conflict, try executing:
- If you get an ip-address through any device, be it a router or a router, then try to go to it and see what’s the matter. In any such device, there is a menu where addresses are issued (for example, DHCP Clients List). In the example, the range of distributed addresses is from 100 to 199. Set it from 20 to 250. As a last resort, restart it . In
- If the reboot did not help, then open the Run window (Shortcut keys Win and R) and enter the command ncpa.cpl . You will open “Control PanelAll Control Panel ItemsNetwork and Sharing Center”. Go to the “Change adapter settings” item in the upper left corner, right-click on your network interface, and try turning it off and on.
- If disabling the interface did not help, then go to the properties of your network adapter and to the ipv4 interface. And so, if you have an IP address conflict on the network, it happens due to the fact that you have the wrong IP address set on the failed computer. Change it to the desired one, or set the receipt of the IP address automatically. If you already have an IP address automatically obtained, then on the contrary, configure a static address different from the conflicting one. All network settings, at best, you need to find out from the network administrator, but if they are not there, then most often the IP-address of the main gateway acts as a DNS server. It is also your router (the box that gives the Internet and WIFI), we prescribe it, and here, the mask in 99% of cases is 255.255.255.0, but the main address will have to be selected to check if it is occupied by someone, without a DHCP server, run before it Everything will be answered if you use the ping command.
- If you have a normal organization and the number of computers is dozens or more, then you just need a DHCP server , which will automatically distribute IP addresses and monitor their use. You can always understand who and what address you have assigned. For example, Cisco equipment has hardwired behavior in the case of a conflict of ip addresses.
If we are talking about Windows DHCP, then there is a function to protect against IP address conflicts. Open the DHCP snap-in and select the IPv4 pool. Right-click on it and select “Properties” from the context menu.
Go to the “Advanced” tab and find the item “Number of conflict detection attempts.” The default value is 0, which means that the service will not first check the IP address for availability before issuing it. We set the value from 1 to 5. This function will eliminate the conflict between the IP address and another system.
The same setting, “Number of attempts to detect conflicts,” can be changed through PowerShell by opening it as an administrator and entering the cmdlets:
As you can see, my desired parameter already has a value of 5, not zero.
To change the “Conflict detection attempts” value, enter the following command:
As you can see, I set a new value of 4. We can check to see that everything has changed. As you can see, PowerShell rules.
I am sure that you now know what to do so that you do not have an IP address conflict on the network and that you can prevent this. Ivan Semin, author and creator of the Pyatilistnik.org computer blog, was with you.
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