CIsco 3845 Static DNS entries (IP host) automatically disappear

Model: Cisco IOS software, 3800 software (c3845-adventerprisek9-m), Version 15.1 (4) M4, RELEASE Software (FC1)

Ios:c3845-adventerprisek9-mz.151-4.m4.bin

Symptom: Write a command such as ' IP host www.test.com 192.168.100.9 ' save, 5 minutes or so this command automatically disappears

Google for a moment:

https://learningnetwork.cisco.com/thread/39482

This is the support of Cisco official website, probably means to restart after the good. The following URLs are referenced https://supportforums.cisco.com/t5/lan-switching-and-routing/ static-dns-entries-ip-host-mysteriously-disappear/td-p/2193285 probably means that it could be an iOS bug.

Method: After writing the command, save, restart, OK

It is not clear whether the bug is iOS or what because I did not update the iOS, the specific solution is not available in the Cisco official website to find the document.

CIsco 3845 Static DNS entries (IP host) automatically disappear