coredns [ERROR] plugin/errors: 2 read udp : i/o timeout

This problem seems to be caused by the failure to resolve DNS, but it is difficult to restart after checking various configurations. Finally, it is found that there is a problem with the forwarding rule configuration. Just execute the following:

iptables -P INPUT ACCEPT
iptables -P FORWARD ACCEPT
iptables -P OUTPUT ACCEPT
iptables -F

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