Nagios is used from HOST1 to check the NTP server on HOST2. One of the servers resides in an ACL. The assumption was that
ip access-list extended vlanX permit udp host HOST1 X Y eq ntp deny ip any any log !
would allow the ntp response, but it results in:
re-sending request to peer 0 NTP CRITICAL: No response from NTP server
while executing the command on HOST2 works. It seems that the NTP has been blocked. How to allow it in the ACL? Note that the ACL works, as PING from specific hosts have to be explicitly allowed by adding new access rules.