communication lost but device is working

[DCIM_Support]

(CID:112626322)

[DCIM_Support]

Hello Mark, 

To better understand lost communication first I would to explain how a device can show lost communication in DCE. DCE using SNMP or ModBus to poll information from the device. During this polling period, if DCE doesn't receive replies via one those communication protocols the device goes into "lost communication". DCE will use this method exclusively to determine communication status. When it comes to troubleshooting here are the general guidelines to why DCE may lose communication to any given device

1. DCE doesn't send out the request
2. The request never reaches the device
3. the device rejects the request due to community strings not be correct
4. the device doesn't respond during the polling period due to processing high priority request or jobs
5. The device responds but the reply never reaches back to DCE
6. DCE is servicing a higher priority request and doesn't process the polling request in time

I would first check community string to confirm that DCE has to correct ones. Beyond that I would recommend that a packet capture to determine the root cause. To be more specific, two packet capture one closest to each end point DCE and the device. 

Thank You

(CID:113641409)

[DCIM_Support]

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