Analysis of IP address conflicts in wireless networks

Wireless network IP address conflicts are one of our most common network failures and are often disabled and enabled. So sometimes this method does not work, then how to solve it? When a wireless access point works as a DHCP server, they can cause two major problems.

The first is to increase the likelihood of IP address conflicts. Most wireless access points on the market are assigned the client wireless network IP address by default configuration, with a range of 192.168.0.x. This is a problem because it is quite common for a network segment to contain multiple wireless access points. If each of these access points is assigned the same DHCP scope, then wireless network IP conflicts will be unavoidable. Keep in mind that these address assignments may not be limited to wireless clients. Many wireless access points also assign IP addresses to wired network clients, so you may encounter a wired network client conflict with a wireless client on your wired network.

Another problem with the default DHCP configuration for most wireless access points is that the 192.168.0.x address range may not be in harmony with the address range you have already used. For example, suppose your network uses a 190.160.25.x address range (I just made up a set of numbers) before any wireless access point is installed. If so, there are two reasons why a wireless access point assigning user 192.168.0.x addresses can cause problems.

To avoid the problem of wireless network IP conflicts, first, clients that have assigned 192.168.0.x addresses will not be able to communicate with a network host using a 190.160.25.x address. The reason is that a client using a 192.168.0.x address range would assume that a host using a 190.160.25.x address is on a different network segment, even if it is not. As a result, they look for routers and try to use the routing table to figure out how to get to the network segment.

Assuming that all two address ranges exist in the same network segment, communication between them is simply not feasible.

Another problem with allowing wireless access points to allocate 192.168.0.x addresses is that these addresses are not routable. If your network is made up of multiple network segments, you will not be able to use this address range.

Now that I've discussed the issue of assigning IP addresses by default for wireless access points, I'd like to talk about how to avoid these problems. First, I would like to point out that some wireless access points are more flexible than others. Not all of the technologies I'm going to mention can work with all the access points.

The best way to prevent wireless network IP conflicts and other communication problems is to decide in advance which address ranges each DHCP server and each access point will manage. This allows you to allow each DHCP server and access point to be IP addresses on demand without having to worry about overlapping.

For example, in my own network, I use the 147.101.x.x address range. Again, I randomly select this address range. Since I have a DHCP server and a wireless access point, I configure the DHCP server to assign addresses from 147.101.101.1 to 147.101.101.100. Then I configure the wireless access point to assign addresses from 147.101.101.101 to 147.101.101.200. In this way, all IP addresses that are likely to be assigned fall into a common scope, but there is no overlap of addresses, which can lead to the risk of wireless network IP conflicts.

When you configure an access point to allocate a specific range of IP addresses in your network, you need to consider the following issues. One of the things you need to consider is that you might use some static IP addresses in your network. You must define an exception for any static IP address in use to prevent the address from being assigned.

In my own network, for example, I have a DNS server that uses address 147.101.101.34. This address belongs to the address range of my DHCP server configuration assignment. Therefore, I have defined an exception so that the DHCP server will never assign 147.101.101.34 to the client.

Another problem you need to consider is that if you configure an access point to assign a unique address to the network, you must also configure the access point to assign a DNS address to the client. If you do not, the client either does not know your DNS server address, or they will attempt to use the ISP's DNS server, which of course will not contain DNS records related to the host in your private network.

As you can see, blindly installing wireless access points may cause a series of problems, because most access points also act as a DHCP server, it is important to decide in advance how new access points fit into your existing IP address scheme, or it can cause wireless network IP conflicts.