Troubleshooting NTP connections - AP10E - AP10A - AP10J - AP10T

AP10 Quick Guide

Document code
English (United States)
Document type
User guide

AP10 must maintain accurate time by synchronizing with a Network Time Protocol (NTP) server. If AP10 does not have accurate time, it shows the messages Not connected to NTP and VaiNet radio off on the home screen. AP10 will not connect any data loggers or transfer any data through VaiNet radio until it is able to synchronize with an NTP server again.

Go through the possible causes of NTP connection problems in the following order. You may need help from your local IT support unless the problem is a simple network connection or configuration issue.

  1. Make sure AP10 is connected to the network:
    1. Check that the Ethernet cable is connected to AP10, and the network activity LEDs on the connector are lit (indicating an active connection).
    2. Check the current network settings from Settings > Network. If you are unsure, confirm the settings from your local IT support. It may also be necessary to register the MAC address of the AP10 to the network so that it can join. The MAC address is written on the front of the AP10 near the Ethernet connector.
    3. Check that AP10 shows the appropriate IP address on its home screen. The message Not connected to network must not be shown.
  2. Verify the NTP servers listed in the Settings > NTP screen. By default, there are four numbered servers listed (for example,

    If you have replaced a default server with a local NTP server, make sure its address is written correctly. If the address of the local NTP server is a hostname (for example, myntpserver), make sure it is registered with the DNS server AP10 is using. Instead of the hostname, you can also try to provide a fully qualified domain name (for example or the actual IP address of the server.

  3. A firewall may be blocking UDP port 123 that is needed for the NTP protocol to function. Typically this happens on the edge of the network. Both inbound and outbound connections must be allowed.

    If you have set up a local NTP server, make sure the firewall on the server itself is not blocking the NTP connections.

  4. There may be a network routing problem. The most typical case is an isolated network with no access to Internet, which means the default NTP servers are not reachable. In an isolated network, you must provide a local NTP server or AP10 cannot be used.
Depending on your geographical location, the default NTP servers may be unreachable even if the access point has Internet access and the firewalls of your local network are not blocking the NTP connections. In that case, you should reconfigure the NTP server list to use country-specific servers. For example, you could use if the access point is installed in Switzerland. For lists of available server addresses, see

For other troubleshooting instructions, see AP10 User Guide (M211860EN) available at