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Event ID: 456 Source: DNS

Source
Level
Description
DNS Server could not connect to DNS server at 171.54.12.77 Data: 0000: 26 27 00 00
Comments
 
As per Microsoft (see link below):

Explanation:
A network problem might have occurred, or the specified DNS server might be down.
User Action:
Use the ping utility to check the server specified in the message. If pinging fails, contact your network administrator to verify that the network is operating properly. If pinging succeeds, check to see if the DNS server service is running on the server. If it is, try stopping and restarting the service by using Services in Control Panel.

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