If you are having trouble establishing video streams the following tips can help you to track down the issue.



Check if the IGMP Querier is setup correctly and recognized by the devices.

Navigate to the Web UI of the receiving V__line. Under “Status” –> “Switch” –> “IGMP” verify that the IP address of the querier is correctly reflected and that the timeout never actually reaches 0:00:



The IP address for the querier should either be the switch (if setup accordingly) or the IP address of the V__line fulfilling that role, but remember that the IGMP querier with the lowest IP address wins the querier election.

If you expect to see the switch, but instead see a V__line, try switching off the querier functionality of that V__line (“Settings” –> “Switch” –> "IGMP” –> “Querier”).

If you do not see a querier on the destination device, this might point to general issues with multicast between source and destination.

If the querier timeout reaches 0:00, the multicast streams will break down, as the source device assumes no one is interested in the stream anymore. The V__lines will re-establish the stream, but there will be an interruption in the video.

General issues with multicast and issues with the IGMP querier can be distinguished from other network issues by switching the stream distribution from multicast to unicast (remember to copy the SDP again – it changes when setting the stream to unicast). If the unicast stream stays stable, look for the issue in the realm of multicast.

In the “Status” –> “Switch” –> “IGMP” menu of the V__line you can also check whether you receive multicast packets by looking at the multicast address vs. interface table. If you see no entry for the multicast IP address or you don’t see a timer running on the interface where you expect to receive the data, the V__line does not receive the respective multicast data. The following screenshot shows missing multicast data for PTP (; no timer running on any interface):


If the data is correctly received on interface 1G/1, you will see a timer running, that never reaches 0:00:





PTP relies on multicast, so if you are having trouble establishing streams, check for issues with multicast first, then come back to PTP.

Check the master’s state:



The master should send out messages (“Announce”, “Sync”, etc. increasing). If the master is not synchronized to an analog reference, it should be in state “Free Run”, else in state “Ref Master”.

If it is in “Passive” mode another device has become master, probably due to higher priority.

If it is in “Recovery” mode the V__line might have been rebooted and is waiting for manual confirmation that it should take over the role of Grandmaster again (only in “Redundant” mode; confirm in “Settings” –> “Switch” –> “PTP” –> “Resume”).


The client should see the correct Grandmaster and its parameters:



You might see the switch's IP address here, if the switch runs in Boundary Clock mode.

Check the client’s state:



The client should be sending out messages (“Ann/DlyResp”, etc. increasing). Once the client has successfully synchronized to the master’s time, it will be “Calibrated”.


If the client cannot reach the “Calibrated” state, check the offset from master and its jitter window:



If the offset or the jitter range is too big, the client cannot synchronize. You can increase the tolerance of the V__line in “Settings” –> “Switch” –> “PTP” –> “Timing Precision” (set to “custom” and enter a new acceptable value). Please keep in mind that this only increases the tolerance of the V__Line; it doesn’t make the PTP better. The unit may still run into trouble with other devices with a lower tolerance level.


If the clients do not recognize the master or if you still cannot get a reliable synchronization, check that all the configuration values (Domain, Sync Interval, Delay Request Interval, etc.) are the same for all devices involved (masters and slaves).


If you cannot get PTP to work reliably (due to multicast issues or jitter which is too high), you can still use the V__line unit's “Virtual Black Burst” feature to synchronize. This, however, requires you to use one of your transmission streams.


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