NTP Server IP Addresses
I have an NTP server that updates its time via GPS. The NTP server has 2 ethernet ports - I am planning on using one for my client-server network (to update the time on my Domain Controllers which do not have 800xA installed on them) and the other for my AC800M network.
The Network Configuration document does not seem to have a recommendation for NTP server IP addresses. Any recommendations?
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You can use whatever IP address you seem fit.
Since GPS most likely can not run RNRP you can freely choose node number within the control network address range.
RNRP Area 20 with 172.16.0.0 base address correspond to: 172.16.80.0 / 255.255.252.0 start with lowest IP address 172.16.80.1 and end with highest IP address 172.16.82.254.
Since a 22 bit mask is used, 172.16.82.254 correspond to node number 766. RNRP can not use any node number over 500 so there is a large number of addresses "free to use" in the upper range of the network address pool, e.g for printers, NAS drives, GPS, and other non-RNRP devices, etc.
I also discourage from creating two links from the NTP source. For each hop, accuracy is less. Some hops later the "two paths" may cross and cause time jitter, etc.
It is better if you create one "time path" through your entire system with falling priority. Most important is probably the PLC, therefore it should be made first line client (I won't argue against a "star coupled" network with first line time client located in the middle).
Since a Domain Controller for natural reasons need to be able to route traffic to the 800xA servers and clients in the system, there exist a physical path for time to be transferred as well.
I recommend letting the AC 800M be the first line client to the NTP source. If each AC 800M PLC shall be NTP slave or not, or be made indirect slaves to the first via CNCP is for you to choose.
Next level of time client is the Connectivity Servers which may pick up CNCP pulses from the primary CNCP master in AC 800M. The AfwTime service (only) should run in this connectivity server (pair). AfwTime will then distribute the time to all other 800xA nodes.
The Domain Controller can either be configured as NTP slave to the connectivity server, or to the AC 800M PLC. The later often require you to install RNRP to create a network route. I do recommend having RNRP on the domain controllers to be able to monitor this (for the 800xA system critical) connection.
Win32Time service should be DISABLED in most computers exept:
- Domain Controller, running as CLIENT to CS or PLC
- Connectivity Server, running as SERVER (only) to DC
Find more information and suggestions in the Network Configuration User's Guide (3BSE034463-510).
I agree with Stefan for the "best solution" except that since the GPS/Time server got two ethernet ports, why not let the DC pick time from the clock directly. Leaving the CS without W32Time enabled and avoid SNTP requests to the PLC/Controller. The DC will get an accurate time synch, no need to be synched in second hand by the 800xA system.
You can use any Non-RNRP address which is greater than 500 like
If you were in area 1 then use the range 172.16.5.245 onwords
If you were in area 20 then use the range 172.16.81.245 onwords
But always try to to do the time sync from bottom to top(controller to CS-All clients and Controller to Domain) for better accuracy.