Cisco Network Manager - weird graph issue

Ben Hart
Ben Hart used Ask the Experts™
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A co-worker is using Cisco's Network Manager to view Kb per second throughput on a Cisco 3750 specifically on the port that is directly connected to the WAN router.

He noticed blank spaces right before a spike hits.  Now we cannot get into the router at all as it's ATT's property but this makes us think the router could possibly be chocking, letting traffic build up then opening the flood walls so to speak.

What do ya'll think? graph
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SouljaSr.Net.Eng
Top Expert 2011

Commented:
I wouldn't say that it's letting traffic build up, but it looks like when utilization get to a certain point the router is unable to send snmp device is unable to read the snmp from the router for a short time, causing the gap.
SouljaSr.Net.Eng
Top Expert 2011

Commented:
Let me state that again.

I wouldn't say that it's letting traffic build up, but it looks like when utilization get to a certain point the send snmp device is unable to read the snmp from the router for a short time, causing the gap.

Author

Commented:
So Network Manager uses SNMP to gather this info?  What if we did not specify any SNMP community strings with regards to the router itself?  By that meaning since we cannot access the routers config, we do not know if SNMP is even enabled let alone what the Read string would be.
Sr.Net.Eng
Top Expert 2011
Commented:
I'm sorry, I misread you question. You are correct. This could be the qos that is configured on the router, so that when it hit  a certain utilization point, it probably puts snmp traffic as a lower priority, thus putting is farther down the queue, causing the gaps in the snmp.
Commented:
Even with data missing, the upward and downward curves clearly show the device was getting hit hard for a few seconds.  It may be that the CPU and/or memory weer maxed out and couldn't process SNMP requests.

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