Showing results for 
Search instead for 
Did you mean: 

IP Conflicts – All In a Day’s Work for a Network Admin

Level 12

Day in day out, network engineers and admins tackle many complex issues. Often, these issues stem directly from an IP conflict. While IP conflicts might seem like one of the simplest problems that occur, they can actually be quite troublesome. How often do you find yourself spending an excess amount of time troubleshooting network issues and then find the reason to be an IP conflict?

We all know what an IP conflict is and ways it can be triggered. The simplest one being the manual assignment of static IP addresses. A misconfigured DHCP server is another reason, where more than one similarly configured DHCP hands out overlapping IP addresses. There is the possibility of IP conflicts occurring if you have multiple wireless access points or other network devices with an embedded DHCP server turned on by default.  DHCP servers also cause conflicts when a statically assigned IP coincides with an address that’s already been assigned by the server. And the most recurrent cause, more so nowadays, is with the increase in devices frequently entering and leaving a network. When nodes like a virtual machine reconnect after an extended period in stand-by or hibernate mode, a conflict is most likely to occur if the address configured on that system was previously assigned to another system that's already in use on the network.

With IP conflicts occurring in various ways across the network, its difficulty lies in troubleshooting and recognizing that the cause of a particular network issue is an IP conflict. Moreover, it’s even more difficult and time consuming to identify and physically locate the devices in conflict.

The Pain in Troubleshooting IP Conflicts

Recent survey results revealed that IT professionals on an average spent 16% of their total time troubleshooting IP problems. One basic and important criterion for efficient IP address management is to avoid IP duplication. IP conflicts pose a threat because they can cause connectivity issues for the systems in conflict. These connection issues are difficult to troubleshoot as the systems experience erratic connectivity. The administrator often ends up looking in a variety of places for the cause before finally identifying the culprit to be IP duplication. Again, the seriousness of the network issue differs when the conflicting system is a simple work station or a critical application server.

For example, say someone brings a notebook into work and plugs it into the network. Soon thereafter, all remote connections to the accounting server go down. Not knowing why, IT starts to investigate the problem. First they reboot the remote access server.  Next, they change the switch port and network cables. Then, as a last resort, they try unplugging all devices from the switch. After that, the problem just goes away. Problem solved, another device was connected to the switch, in turn causing the problem.  In this scenario, IT started looking for an IP conflict and much later found the outside computer plugged into the network to be the problem. Consider all the time spent troubleshooting this issue? In the end, many hours are lost troubleshooting and the business likely suffers downtime.

As a network engineer or admin, you’re often under the gun to resolve issues with the least amount of downtime. But hey, you don’t have to be…there’s always a peaceful resolution. So, how do you avoid excessive troubleshooting time or at least limit it? Do you use spreadsheets or an IP management tool?

1 Comment
Level 15

Good information and educational article.  Thanks for sharing.