Discussion on DHCP server troubleshooting

In the previous article, we explained the ideas about DHCP server troubleshooting and some troubleshooting methods for clients. I hope to help you solve some problems.

Server troubleshooting:

We have already introduced the troubleshooting methods for DHCP servers. Interested readers can refer to previous articles on server channels. The main method is to check whether the dhcp server settings on the server are normal. If it is not enabled, enable it. In addition, you need to disable the DHCP server from time to check whether there are other DHCP servers in the network, resulting in conflicts. In addition, if you want to enable the DHCP server when creating a domain on the network, you must authorize the DHCP server by the domain control. Therefore, do not forget the authorization work.

The lease problem also needs to be raised. If DHCP works properly, some clients cannot obtain IP information. If ipconfig/renew is executed, the system prompts that the DHCP server cannot be found, if the other part can be obtained normally, 90% is due to the lease. If too much information is saved in the lease, We need to manually clear it once. If so, the lease time is too long, as a result, a large number of illegal MAC addresses occupy valid IP addresses.

TIPS: any server that provides the DHCP service must have a fixed IP address. It is not allowed to enable the DHCP service on a computer that dynamically obtains IP information. In addition, Microsoft has made regulations on the restriction of DHCP service. For example, two DHCP servers are not allowed in the same network. However, there are currently many third-party software that can be used to build DHCP servers, and even broadband routers integrate DHCP functions into their own configurations, therefore, in this case, it is impossible to clearly query whether several DHCP servers exist in the network, we can only disable the suspicious objects one by one or filter out the suspicious objects on the vswitch and vro. In short, it is very difficult to solve network faults caused by illegal DHCP servers in the network, and it is necessary to investigate and step by step.

Conclusion: When the DHCP service encounters a problem, do not blindly search for the result on the server. Most of the time, it is caused by client faults. In addition, the media between the client and the server should also be worth noting, whether the network cable is connected normally or whether the switch is working normally requires consideration. If necessary, replace it with several network cables or several switch ports. Remember not to take it for granted. You must make a down-to-earth measurement to get real results.