PTP 650 DISARM problem


we have a PTP 650, that is showing Link UP and can ping from one side to the other of the microwave. It is set at 64 QAM single and showing actual capacity aboout 40 Mbps.  However when we disarm, the link remains UP but we lose reachability betweeb the two sites, we cannot ping or reach the other site. Have you seen this before?


Could you please share the Field diags from the radios, so we can check what might be causing this issue.

Please send us the Field Diags from both sides of the link.
Here you have the procedure of how to retrieve field diags:
1) Open web browser and type in IP address of first radio
2) Go to system administration in order to complete logon process (you must logon to get field diags)
3) After logon, type into your address bar: http://xx.xx.xx.xx/field_diags.cgi
4) Click on the link displayed and download the file somewhere where you can easily find it
5) Repeat same process for 2nd radio
6) ZIP both generated files and send it across to us.


Hardik Patel


the problem got resolved by lowering the modulation. for QAM 256 the link was operational but only when armed. when the  link was disarmed the link dropped. At QAM 64, the link worked for arm and disarm

Good to hear that it is working now, but this is strange.

The link may not stay at the max modulation in case if there is interference on the selected channel and it will drop the low modulation(Adaptive modulation) but it still cannot expian the reachability issue.

If you like, you can still share the diags file just so we can check if we can find something when it is on max modulation.


Hardik Patel

Remember that the ODU always transmits at BPSK when Armed, regardless of the maximum modulation mode configured.

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thanks, will  try to get them if we can. we had to finish in a hurry and couldn't get the data.

The link has Maximum receive modulation and Low data modulation.  is the low data modulation, the lower limit that the modulation will drop to?  the manual says it is the lowest modulation for packets to be bridged, which is not too intuitive.

This is what we have in the User Guide:

Lowest Data Modulation Mode

The PTP 650 ODU can be configured to discard Ethernet frames in the Data Service when the modulation mode is lower than the configured Lowest Data Modulation Mode.

This feature is likely to be useful in networks that have alternate routes, for example in a ring or mesh topology where EAPS or RSTP is used to resolve loops. In this application, Lowest Data Modulation Mode should be set to ensure that an active link will provide at least the minimum necessary capacity for high-priority constant bit rate traffic such as voice over IP or TDM pseudo wire. An active link will be blocked when the capacity falls below the minimum required, triggering a routing change in associated Ethernet switches to bring alternate links into use.

Lowest Data Modulation Mode should normally be set to BPSK 0.63 Single in simply connected tree networks or other topologies that do not have alternative routes.

Does this help?


yes makes sense thank you.