Tips for Solving DHCP Server Failures Completely

If you use DHCP to automatically configure TCP/IP for workstations in your system, any DHCP failure can cause the service to crash. After all, if a workstation can't get an IP address, there is no way to read any resources on the personal network or the Internet. In this article, I will introduce some techniques that can be used to troubleshoot DHCP servers.

improper address assignment


a very common DHCP related issue is the unexpected IP address assignment. For example, suppose your DHCP server's IP address range is configured from 192.168.0.1 to 192.168.0.50. You want the host computer to be assigned an IP address in this range. Now, suppose that a workstation from your network is communicating with a web server and seems to have problems. You send an IPCONFIG/ALL command to view the workstation's IP address configuration. In contrast to the expected address range, the work is assigned an address starting with 169.254.

What happened? If a host from your network was accidentally assigned an address starting with 169.254, you can confirm that the address was not assigned by your DHCP server. This means that the workstation cannot communicate with the DHCP server. When this happens, the workstation will assign itself an IP address using a Windows feature called Automatic Private IP Addressing (APIPA).

Microsoft automatically establish a dedicated IP address to the window, to help those who have a small network of machines. For example, if you are building a small Windows network, you don't need to manually configure the IP address even if there is no DHCP server on the network. APIPA will automatically assign a unique Class B IP address to each machine on the network. This is great for small home networks, but not at all for larger networks.

If a workstation rely on APIPA assigned address, it is because it requests an IP address does not get a response. There are several possible reasons for this problem. Assuming that other computers on the network can get an IP address from your DHCP server, you can troubleshoot the DHCP server.
It is highly probable that this problem is related to network hardware failures installed in the workstation. For example, a network interface card is assigned an incorrect driver. Another possible reason is that the network cable is not plugged into the network interface card, or there is no switch connected to the other end. //This switched www.45it.com computer hardware and software applications network

Of course, just because a computer on the network has a problem in terms of obtaining an IP address can not completely eliminate the problem server. If other workstations can successfully obtain an IP address, then you can be sure that the server is working properly. However, it is also possible that the server has already allocated the available IP address. By comparing the number of devices on the network requesting IP addresses from the DHCP server to the size of the DHCP address range, you can easily tell if the IP address is exhausted.

common DHCP server problems


experience problems if multiple workstations leased IP addresses, then the problem may be related to the DHCP server itself. If you suspect that DHCP is the cause of the problem, then you can start detecting problems by using some Ping tests to confirm that DHCP can communicate across the network.

If the DHCP server can communicate with other computers on the network, then I suggest the DHCP server to verify whether there is compliance with a range of IP addresses, and the server is configured for the specified address. For example, if the address range of the DHCP server is from 192.168.0.1 to 192.168.0.50, the server cannot actually allocate these addresses unless the server itself has assigned a static address, such as 192.168.0.0 or 192.168.0.51, within the same subnet.

If this still does not solve the problem, then I recommend checking the basic configuration. For example, you should ensure that the DHCP server is still authorized by the current directory to lease IP addresses. You should also check to make sure that the IP address range is still valid and that the necessary services are running on the DHCP server.

IP address conflict issues


another occasional involving dynamic configuration is the IP address conflict. When you create a DHCP scope, the responsibility of the DHCP server is to ensure that the addresses in the range can only be leased to one user at a time. In that case, IP addresses how conflicts may occur when dynamic address assignment it? IE browser browse Taobao

problem I encountered two situations may cause this problem. The first time I encountered it, I was able to decide which PC was assigned to a duplicate address. When I checked the TCP/IP on these machines, I found that the IP address of one of the machines was manually configured. It's a long story, but the user of that machine runs an unauthorized application and needs a static IP address. Users feel that reconfiguring each time they use the application is cumbersome, so they use the address that is dynamically assigned to them and treat it as a static address.

The possibility of this happening today is very small. I used Windows 98 in the specific case mentioned above. Windows 98 lacks many of the security mechanisms we take for granted today. A workstation with normal security and Windows XP or Windows VISTA should be able to prevent end user reconfiguration. Even so, I think at least should pay attention to this problem, because if you have problems in solving this problem, you will be well documented.

reason for the problem is a more general multiple DHCP servers are in use, and those DHCP server address ranges overlap. If you have only one DHCP server in your network, don't ignore the cause of the problem. In all likelihood, there is an illegal DHCP server that is in conflict with your primary DHCP server.

Windows 2000 Server and Windows Server 2003 are designed this way to prevent illegal DHCP server causing the problem. The DHCP server can only send addresses after being authorized by the current directory. The problem is that this is only suitable for DHCP servers under the Windows platform. The DHCP server running on other operating systems leases the IP address to the user for free, and does not need to be authorized by the current directory.

so users really suffered trouble to install the DHCP server on Linux platform yet? Probably not. A more likely explanation is that a wireless access point, or a router for a cable or DSL Internet connection, causes problems. Most of these devices have DHCP. These devices typically use a range of 192.168.0.x or 192.168. 1.x. If you happen to be using the same IP address as your primary DHCP server, then you are in such a dilemma that both DHCP servers use the same address resource to publish the address!

Conclusion

DHCP There are many potential causes of failure. In most cases, these failures are related to communication problems between the DHCP server and the workstation attempting to lease the address.