NETTIME and proper setup

[Bolt]

Seems to me like you have some sort of firewall/traffic restriction. I know that here at work, I can't ping those servers, but my internet access works allowing me to ping things like google, etc. You might look at what kind of restrictions your network has in regards to network traffic. Corporate IT is my nemesis.

I don't think that's the issue, either.  I am my own IT guy, and have very few restrictions on traffic.

This one worked for me: utcnist.colorado.edu

I can also ping that one from command prompt in Windows.  With slightly better performance than a ping to google.com.

[BobO]

This one worked for me: utcnist.colorado.edu

I can also ping that one from command prompt in Windows.  With slightly better performance than a ping to google.com.

If you hardcode NETTIME to that server, and then attempt to ping from the PLC when it fails, what happens?

[Bolt]

This one worked for me: utcnist.colorado.edu

I can also ping that one from command prompt in Windows.  With slightly better performance than a ping to google.com.

If you hardcode NETTIME to that server, and then attempt to ping from the PLC when it fails, what happens?

I get about a 70% success rate getting a time from that server too. When it fails, a ping also fails 100% of the time. A ping does work from DmD when manually triggered however.

[BobO]

I get about a 70% success rate getting a time from that server too. When it fails, a ping also fails 100% of the time. A ping does work from DmD when manually triggered however.

Everything you are describing points to some kind of general network instability.

Host's primary internet connection is fiber, but we have a backup copper line that works great...and then doesn't. Never could figure out exactly why it would go wobbly. From our desks it still appeared to work, but the packet losses would shoot way up for a bit and then it would be fine.

[Bolt]

I spoke too soon.  I changed my logic up via remote desktop, and didn't enable the alternate bit to force everything over to the colorado IP address.  It has run 100% over the last 50+ attempts.  So it was also pinging the non-pingable IP address in the mean time.  Doh!

[Dean]

After two systems with a hard coded IP, changing the addresses a few times, and having inconsistent results, I went with Bob's suggestion of using DNSLOOKUP on time.nist.gov and feeding it into NETTIME, (Which couldn't be simpler by the way, thanks guys.) Haven't had a failure since.

[Bolt]

Strange.  I can go 100% on 260+ attempts with utcnist.colorado.edu, then go back to time.nist.gov, get 1 failure right away, it won't ping, and go back to utcnist.colorado.edu, and it succeeds again. 

[Controls Guy]

Maybe the DNS server in use by your provider has a messed-up entry for time.nist.gov.   Can you ping it from the desktop while getting interwebs from the same network?  And, if you resolve the IP address elsewhere, can you ping it from that network with the explicit IP?

[Dean]

Another option is pool.ntp.org. These servers don't get as much traffic as the NIST servers, have a higher service capacity, and automatically route your request to your nearest server.