Why does PTP synchronization fail when IGMP Snooping is enabled?
PTP (Precision Time Protocol) uses multicast communication to synchronize GigE cameras. TIS GigE cameras send PTP synchronization messages to the multicast address 224.0.1.129.
When IGMP Snooping is enabled on a managed network switch, the switch selectively forwards multicast traffic only to devices that have joined the corresponding multicast group. This helps reduce unnecessary multicast traffic on the network.
However, TIS GigE cameras do not join an IGMP multicast group for PTP communication. As a result, a switch with IGMP Snooping enabled may block the PTP synchronization messages, preventing the cameras from synchronizing correctly.
How can I enable PTP synchronization?
If PTP synchronization does not work when the cameras are connected through a managed network switch, check whether IGMP Snooping is enabled.
To allow PTP multicast traffic from TIS GigE cameras, disable IGMP Snooping on the network switch.
This allows the PTP synchronization messages sent to 224.0.1.129 to reach the cameras as required.
What can I do if the cameras remain PTP Masters after disabling IGMP Snooping?
After disabling IGMP Snooping, one or more cameras may initially continue to operate as PTP Masters. This does not necessarily mean that the camera is unable to update its PTP state correctly.
Instead, the managed network switch may not yet be forwarding PTP multicast packets to the corresponding port. In this case, the camera does not receive the PTP messages it needs to determine the appropriate PTP role and, if applicable, switch from Master to Slave.
How can I restore PTP communication?
In many cases, it is sufficient to reset the connection to the affected switch port. For example, you can briefly disconnect and reconnect the RJ45 network cable. This re-establishes the link and typically causes the switch to update the configuration of the corresponding port.
Alternatively, you can restart the camera. This also re-establishes the network connection and allows the camera to initialize PTP synchronization again.
Note: In this situation, the cause is not necessarily related to the camera. The important factor is that, after IGMP Snooping has been disabled, the managed network switch resumes forwarding PTP multicast traffic correctly to the relevant ports.
In summary
If PTP synchronization between TIS GigE cameras does not work through a network switch:
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Check whether IGMP Snooping is enabled.
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Disable IGMP Snooping on the relevant managed network switch.
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If the cameras remain in the wrong PTP role, power-cycle the cameras.
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Check again whether the cameras synchronize correctly.
Note: IGMP Snooping is a standard network feature designed to control multicast traffic. Disabling it may increase multicast traffic on the network. If IGMP Snooping is required by the overall network architecture, consult the switch manufacturer's documentation to determine whether the switch provides a configuration that allows PTP multicast traffic to 224.0.1.129.