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MyLAN is composed by a S8 (core switch) 40 switch (C  & B series). All the switches are connected to S8 by 1G link. The LAN is monitored trought NetSight Many times during the day, NenSigt shows "SNMP CONTACT LOST NO SNMP REPLY FROM DEVICE" The link goes DORMANT or DOWN. It takes about 2 minutes before the switch starts working again. It is a SNMP configuration problem? May I make some test or check S8 configuration? I need some help!!!!
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Posted 2 years ago

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Jeremy, Embassador

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What version of SNMP are you using?  I have seen NS struggle polling lots of devices if you're not using SNMPv3 on a decent server.
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Bastian Sprotte, Employee

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you should same areas to understand the situation,

check is STP is stable:
show spantree stats active
verify that the "Topology Change Count" is not rising and "Time Since Top Change" is growing.

as next, ensure you not have loops.
set logging here enable
set movedaddrtrap enable
set movedaddrtrap *.*.* enable

If loops happen, this will shown as MAC-moves

This command show you if Links are real flapping
show linkflap currentcount

If links toggle you see that on the counter

This are the steps you should start with.

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Erik Auerswald, Embassador

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I am not quite sure about the following part of your question:
The link goes DORMANT or DOWN.
Which link goes down? The link to the monitored device where contact has been lost? If so, then the down link would explain the contact lost message.

A port status (show port status) of dormant means that the port is part of an LAG. If the corresponding LAG (lag.0.X) is up, this is fine. The word dormant tells you to look at the corresponding LAG.

If you do not intend to use a LAG on this port, you should disable LACP (set port lacp port PORTSTRING disable).

A port status of down means that the Ethernet port is inactive. There may be many reasons for this.