Today, colleagues said their side of a user of a wireless SSID can not obtain an IP address, the rest are still normal. Wired also includes access to normal and get the address.
Because the whole company's problems, I'll just log on to the domain controller, looked DHCP, IP address pool as well as it also did not show that there is full of blue exclamation point. But I found that some should not be connected to this SSID is not even addresses, I tried to remove them, suddenly found a DHCP error.
It is customary think DHCP service problems, because in general when making fast recovery problem, not so much time to see the log.
I went in the service, the DHCP service restart it, the normal DHCP pool, we can only see three addresses have been issued, local IT feedback or that can not obtain an IP address.
Charles is a problem as the DHCP server, usually after restart the service, you will soon be able to see the address distribute it. DC suspect this was out of the question, anyway, the fastest way to solve the problem is to restart, but this is a VM, reboot too fast, also two minutes to complete the restart. The results still does not solve the problem.
Then I began to suspect that the WLC controller, remote I opened the main and standby of WLC WLC, check the configuration, all the normal way. And the interface is correct address configuration related, there is no alarm.
I would like to look at the other side of the core and the associated access layer switch configuration, under normal circumstances, no one would move these configurations, suddenly appeared abnormal Core 2 switch, which is able to ping, but can not connect.
I let go check that the local IT devices, found that the core switch interfaces are mad busy all the yellow light, the solution is to restart this visit. The question then back to normal.
Remote biggest uncertainty when troubleshooting a problem that can not see the device status, it will take some detours, solve network problems also pay attention to the look and smell. See the state it is difficult to find problems.