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SNMP painfully slow

On SG500, SG300 and SG200 series switches, SNMP is painfully slow.

When I snmpwalk the switch, it dumps about 30 to 40 entries, pauses for a second, then dumps another 30-40 entries, pauses for a second, etc.

Multiple snmpget requests cause the snmpget to timeout becuase the switch didn't respond.  Monitoring traffic on stacked switches is basically impossible because of this due to the snmp timeout. 

1) why does this happen


2) how can I fix it?


SNMP painfully slow

Are you trying to walk the entire mib library? How many connected devices are there..?

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-Tom Please mark answered for helpful posts
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SNMP painfully slow

I'm not specifically walking the entire tree, but I see the same symptoms when I do walk the entire tree.

This is on a set of 2 SG500-52P's stacked as a single manageable unit.  I'm walking the PoE power usage tree in order to obtain the total PoE power usage for the entire stack.    It takes about 15-20 seconds to complete this walk, during which time it seems other snmpget requests for other metrics (port bandwith, etc) are delayed and/or blocked until it is done.

Can the SG's only hangle one snmp session at a time?

The stack is pretty much fully populated with copper links and 3 fiber links.  All at 1 Gb/s.  A few LAG groups are setup as well.

The CPU usage on the stack as seen through the web interface is low even when the snmpwalk is timing out.

I've only had this issue on the SG series of switches.  Any other cisco product (true IOS product) snmpwalk is blazing fast.  I've done this same thing on catalysts with higher port density with no issues at all.


Re: SNMP painfully slow

Hi Dan, this is a tough symptom.

I have stacked 2 sx500 and some sx300 cascaded off my stack and running a complete walk I'm not hanging. But obviously my lab is not production nor as many statistics to report.

Can you log in to the cli while you perform the walk?

Use these commands multiple times over while performing the walk.

show cpu input rate

show cpu utilization

Also is the switch operating layer 2 or layer 3?

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-Tom Please mark answered for helpful posts
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Re: SNMP painfully slow

Layer 2

It's now happening on a SG500-28P as well, I happened to catch it on the 28P as it's quite sporadic when it happens. 

I am requesting snmp traffic metrics for 26 ports via snmpget, those reqeusts get sent at the same time.  All of the requests timed out after waiting for a response for 20 seconds.

five seconds: 65%; one minute: 21%; five minutes: 16%

Input Rate to CPU is 21 pps

This particular switch only has 4 connected devices.  3 copper, one fiber.


Also, off topic for this, but do you know the snmp OID for Fan status, CPU usage, and memory usage on the SG series?  I can't find it for the life of me, and it's something I need to monitor as well.

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