About DHCP server faults

Do you have many problems with DHCP servers? If you use DHCP to automatically Configure TCP/IP for the workstation in the system, any DHCP failure can cause service crash. After all, if a workstation cannot obtain an IP address, it cannot read any resources on the personal network or the Internet. In this article, I will introduce some technologies that can be used to resolve DHCP server faults.

Improper IP Address Allocation due to DHCP server failure

A very common problem related to DHCP is accidental IP Address allocation. For example, assume that the IP address range of your DHCP server is 192.168.0.1 to 192.168.0.50. You want the computer host to be assigned an IP address in this range. Now, it seems that a problem occurs when a workstation on your network communicates with a network server. You can send an IPCONFIG/ALL command to view the IP Address Configuration of the workstation. In contrast to the expected address range, work is assigned an address starting with 169.254.

What happened? If the host from your network is accidentally allocated an address starting with 169.254, you can confirm that this address is not allocated by your DHCP server. That is to say, the workstation cannot communicate with the DHCP server. In this case, the workstation will assign an IP address to itself based on the Windows feature named automatic private IP address (APIPA.

Microsoft automatically creates dedicated IP addressing to Windows to help machines with small networks. For example, if you want to build a very small Windows network, even if there is no DHCP server on the network, you do not need to manually configure the IP address. APIPA automatically assigns a unique Class B IP address to each machine on the network. This is ideal for small-sized home networks, but is not suitable for larger networks.

If a workstation relies on APIPA to allocate an address, this is because it does not receive a response to the requested IP address. There are several possible causes for this problem. If other computers on the network can obtain an IP address from your DHCP server, you can eliminate the problem of the DHCP server.

Most likely, this problem is related to network hardware faults installed on the workstation. For example, a network interface card is allocated with an incorrect driver. Another possible cause is that the network cable is not inserted with the network interface card or is not connected to the switch at the other end.

Of course, server problems cannot be completely ruled out only because a computer on the network has problems in obtaining IP addresses. If the IP address can be obtained successfully from other workstations, the server will certainly work normally. However, it may also be because the server has allocated available IP addresses. By comparing the number of devices requesting IP addresses from the DHCP server over the network with the DHCP address range, you can easily identify whether the IP address is exhausted.

Common DHCP server faults

If multiple workstations have problems with the rented IP address, the problem may be related to the DHCP server itself. If you suspect that DHCP is the cause of the problem, you can use some Ping tests to confirm that DHCP can communicate across the network to start detecting the problem.

If the DHCP server can communicate with other computers on the network, we recommend that you check whether the DHCP server has an IP address that complies with the configured IP address. For example, if the IP address range of the DHCP server ranges from 192.168.0.1 to 192.168.0.50, the server cannot allocate these IP addresses unless the server itself has allocated a static IP address within the same subnet, for example, 192.168.0.0 or 192.168.0.51.

If the problem persists, we recommend that you check the basic configuration. For example, you should ensure that the DHCP server is still authorized by the current directory to lease IP addresses. Check whether the IP address range is valid and the necessary services are running on the DHCP server.

IP address conflict in DHCP server faults

Another occasional problem occurs when the dynamic configuration address is an IP address conflict. When creating a DHCP range, the DHCP server is responsible for ensuring that the addresses in the range can only be rented to one user at a time. In that case, how can an IP address conflict occur when an IP address is dynamically allocated?

I have encountered two possible causes. When I first met, I was able to decide which PC was allocated to a duplicate address. When I check the TCP/IP on these machines, I find that the IP address of one of them has been manually configured. However, the user of the machine needs a static IP address to run unauthorized applications. Users think it is difficult to reconfigure the application every time they use the application, so they use the address dynamically allocated to them and use it as a static address input.

This situation is very unlikely today. In the specific situations mentioned above, I use Windows98. Windows 98 lacks many security mechanisms that we take for granted today. A workstation with normal security protection and Windows XP or Windows VISTA should be able to prevent end users from reconfiguration. Even so, I think you should pay attention to this problem at least, because if you have any problems in solving this problem, you may be well documented.

A more common cause of this problem is that Multiple DHCP servers are in use, and the IP ranges of those DHCP servers overlap. If you only have one DHCP server in your network, do not ignore the possible causes. An invalid DHCP server is in conflict with your main DHCP server.

Both Windows 2000 Server and Windows Server 2003 are designed in this way to prevent problems caused by Invalid DHCP servers. The DHCP server can only send addresses after being authorized by the current directory. The problem is that this is only applicable to DHCP servers on Windows platforms. DHCP servers running on other operating systems rent IP addresses for free and do not need to be authorized by the current directory.

So have users really suffered the trouble of installing the DHCP server on the Linux platform? May not. It is more likely to be explained that a wireless access point or a router connected to a cable or DSL Internet causes problems. Most of these devices have DHCP. These devices usually use a range of 192.168.0.x or 192.168. 1. x. If it happens that the IP address is the same as the IP address used by your primary DHCP server, you are in such a dilemma that both DHCP servers use the same address to publish resources!

DHCP server fault conclusion

DHCP faults have many potential causes. In most cases, these faults are related to communication problems between the DHCP server and the workstation trying to lease the address.