GE Industrial Solutions Entellisys 4.0 System Administrator Manual - Manual (Page 25)

Using an external time server 25
5
• To verify each device is communicating, ping each device using a laptop connected to the
CPU/HMI LAN
• If the lineups are in close proximity of each other a network cable can be routed between
them (300ft is the maximum recommended length for Cat 5E cable)
• If existing network infrastructure is used, VPNs must be installed at each lineup (see Network
security/VPN device on page 33 .). It is recommended that a dedicated Control LAN be used
to ensure the highest degree of accuracy
• The VPN must be configured to allow port 123 (SNTP uses port 123 - which is normally
blocked on the VPN)
NOTE: If Entellisys is connected to the building LAN, VPNs must be used to prevent unwanted
traffic on the Entellisys network.
5.4 Using an external time server
If the time stamps on system events need to be synchronized to absolute time then a 3rd party
time server may be used.
Time Server requirements:
• Time server that supports passive SNTP
• The time server is connected to the Entellisys VPN