Solutions to IP address conflicts in Wireless Networks

In the wireless network world, wired and wireless networks coexist, and there are also a variety of problems. For IP conflicts that often occur, let's introduce and solve them here.

When wireless access points work as DHCP servers, they may cause two major problems.

The first is to increase the possibility of IP address conflict. Most wireless access points on the market use the default configuration to allocate the client's wireless network IP address in the range of 192.168.0.x. This is a problem because it is quite common to include multiple wireless access points in a network segment. If each of these access points is assigned the same DHCP scope, the IP address conflict in the wireless network is inevitable. Remember that these addresses may be allocated not only to wireless clients. Many wireless access points are also assigned IP addresses to wired clients, so you may encounter conflicts between wired clients and wireless clients on your wired network.

Another problem with the default DHCP configuration for most wireless access points is that the address range of 192.168.0.x may not be consistent with the address range you have used. For example, suppose that your network uses the address range of 190.160.25.x before any wireless access point is installed (I just compiled a set of numbers ). If this is the case, there are two reasons to explain why a wireless access point assigns a user address 192.168.0.x, which may cause problems.

To avoid IP address conflict, clients with 192.168.0.x addresses cannot communicate with network hosts that use the 190.160.25.x address. The reason is that the client that uses the 192.168.0.x address range will think that the host with the 190.160.25.x address is in different network segments, even if not. Therefore, they will look for the router and try to use the route table to calculate how to reach the CIDR block.

Assume that both addresses are in the same CIDR block, and communication between them is not feasible.

Another problem that allows wireless access points to allocate 192.168.0.x addresses is that these addresses cannot be routed. If your network is composed of multiple network segments, you cannot use this address range.

Now I have discussed the problem of default IP Address Allocation for wireless access points. Next I want to talk about how to avoid these problems. First, I want to point out that some wireless access points are more flexible than others. Not all technologies I will mention can work with all access points.

The best way to prevent IP address conflicts in wireless networks and other communication problems is to determine the address ranges managed by each DHCP server and each access point in advance. In this way, you can assign IP addresses to each DHCP server and access point on demand without worrying about overlap.

For example, in my own network, I use the address range of 147.101.x.x. Similarly, I randomly select this address range. Because I have a DHCP server and a wireless access point, I configure the DHCP server to allocate addresses from 147.101.101.1 to 147.101.101.100. Then I configure the Wireless Access Point to allocate addresses from 147.101.101.101 to 147.101.101.200. In this way, all IP addresses that may be allocated will fall within the same range, but there is no overlapping addresses, resulting in the risk of IP address conflict in the wireless network.

When you configure an access point to assign a unique IP address range in the network, you need to consider the following issues. One of the issues you need to consider is that you may use some static IP addresses in the network. You must define an exception for any static IP address in use to prevent the address from being allocated.

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

Another issue you need to consider is that if you configure an access point to allocate a special address in the network, you must configure the access point to allocate a DNS address to the client. If you do not, the client does not know your DNS server address, or they attempt to use the ISP's DNS server, of course, this does not contain DNS records related to hosts in your private network.

As you can see, blind installation of wireless access points can lead to a series of problems, because most access points also act as DHCP servers, it is very important to determine how the new access point fits your existing IP address scheme in advance, otherwise it will lead to a wireless network IP address conflict.