Version

Argent Advanced Technology 3.1A-1504-T8 or earlier

Date

Monday, 13 July 2015

Summary

DeviceMagic in Argent for SNMP monitors port status of SNMP devices

An SNMP device might not have all ports used or connected

In order to avoid Event being fired for those unused ports, flag ‘Ignore Port Status’ can be set

However, it is found that the settings might be lost over time especially for busy network with more than 300 SNMP devices monitored

The root cause is that UDP protocol on which SNMP is built on provides data integrity but does not guarantee the delivery

The issue has been addressed in Argent AT 3.1A-1504-T9

Technical Background

DeviceMagic Rule scans all available ports in the monitored SNMP device

Internally it uses SNMP GetNext command to enumerate all the ports according to RFC1214

The results are sent back to Supervising Engine to save in SQL table ARGSOFT_SN_NODE_PORT where the flag ‘Ignore Port Status’ is also stored

Supervising Engine adds, edits or deletes the port record based on the scanning results

It is found that DeviceMagic Rule might not pick up all the ports

Following messages can be found in the Monitoring Engine log:

SSNMPManagerBase::GetBridgePortTable: Method ‘SendGetNextRequest’ failed (301). Error: noError (0)

It is explainable that UDP protocol on which SNMP is built on is not a delivery-guaranteed protocol

When network is busy, switch and router can optionally drop the SNMP packets

When a port is missing from the scanning result, Supervising Engine deems the port as no longer available

So it deletes the correspondent record from SQL table ARGSOFT_SN_NODE_PORT

As a result, the setting ‘Ignore Port Status’ is also deleted for the port

When the port is picked up again in next scan, all the port information is restored

However, the setting ‘Ignore Port Status’ is lost permanently

Argent AT 3.1A-1504-T9 has enhanced the code so that a DELETE flag is set for the port record instead of deleting the entire record

When the port record is restored in next scan, the setting ‘Ignore Port Status’ is also restored

Resolution

Upgrade to Argent AT 3.1A-1504-T9 or later