我正在运行一个 Ubuntu 服务器 (18.04.1)，几天后我在系统日志中看到这些消息：
systemd-resolved[1059]: Server returned error NXDOMAIN, mitigating potential DNS violation DVE-2018-0001, retrying transaction with reduced feature level UDP.
在收到这些消息时，我无法从外部世界访问我的服务器，只能从我的内部局域网访问。需要几分钟时间，然后可以从其域名再次访问服务器。
系统日志的输出：
11/5/18
1:51:02.000 PM
Nov 5 13:51:02 server systemd-resolved[1059]: message repeated 12 times: [ Server returned error NXDOMAIN, mitigating potential DNS violation DVE-2018-0001, retrying transaction with reduced feature level UDP.]
host = server source = /var/log/syslog sourcetype = syslog
11/5/18
1:50:59.000 PM
Nov 5 13:50:59 server systemd-resolved[1059]: Server returned error NXDOMAIN, mitigating potential DNS violation DVE-2018-0001, retrying transaction …