Users may observe the minor alarm "PEM X Feed X switch OFF but input connected" being reported in the show chassis alarms output if the Input (INP) DIP switches are in the OFF position in MX960 and MX10K devices.

This article explains that it is essential to have the DIP switch corresponding to each power feed on every PEM set to "ON" in order to prevent these alarms.

If the Input (INP) DIP switch is OFF but the feeds are connected, the following minor alarm may be reported:

Alarm time               Class  Description
2018-01-01 01:01:01 UTC  Minor  PEM x Feed x switch OFF but input connected

The alarm message "PEM X Feed X switch OFF but input connected" is reported when the DIP switch on the PEM is not set to the "ON" position despite having the power feed connected.

To prevent these alarms, it is essential to ensure that the DIP switch corresponding to each power feed on every PEM is set to "ON".

NOTE: Flipping the DIP switch will not impact traffic. However, it is recommended to do so in a maintenance window to avoid unforeseen circumstances.

Note that the DIP switch positions differs across platforms. Here we have shown the DIP switch position across MX Power Supply models. You would need to ensure that the corresponding DIP switches are "ON."

DIP Switch Positions across multiple MX PS Models

1. PWR-MX960-AC - Single Inlet - Normal MX PS - No DIP Switch

2. MX960-PSM-HV - Single Inlet - High-Voltage Second-Generation Universal (HVAC/HVDC) Power Supply - No DIP Switch 

3. MX960-PSM-5K - High-capacity second-generation AC - DIP Switch Available

DIP Switch Positions

• Position 0: Indicates that only one AC feed is provided

• Position 1: Indicates that two AC feeds are provided

4. PWR-MX960-4100-AC - High-capacity AC -  DIP Switch Available

PWR-MX960-4100-AC

5. PWR-MX960-4100-DC - High-capacity DC -  DIP Switch Available

PWR-MX960-4100-DC

DIP Switch Positions

• Position 0: Indicates that only one DC/AC feed is provided

• Position 1: Indicates that two DC/AC feeds are provided

Note for troubleshooting DIP switch issues

When the DIP switch is in position 1 with two feeds connected and the alarm is still seen, you would need to troubleshoot further to understand the cause for the alarms such as problems with circuit breakers and feeders or verify whether it is a real hardware issue.

Check the power feeds to the PEM that is generating the alarm:

• Make sure that the power leads are properly secured to the PEM inputs.

• Make sure that there is power to both leads.

• Make sure that no circuit breakers have tripped, or fuses blown in the facility DC circuits.

Monitor the time of alarm generation, compare it with the system uptime, and assess whether the issue has been present from day 1 or has manifested due to recent failures.

If there is only one power feed for the PEM, move the dipswitch to position 0.

CAUTION: The above steps should be performed only by someone trained and qualified in DC power operations.

If neither of the above steps resolves the alarm, open a case with your technical support representative to investigate the issue further.

This is a feature introduced with PR1311574 - PTX10K/MX10K: Suppress chassis alarm for switched off PEMS to indicate the Input (INP) switches are set OFF but the feeds are connected.