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High load due to SNMP monitoring

[ Edited ]
Tuesday

Hi there,

 

we have a virtual chassis with 6 EX4300 members.

The firmware version is: 18.2R1.9

 

We have high CPU usage on the primary routing engine.

This load is caused by our SNMP monitoring. We query normal values. For example, temperature, CPU usage or just the traffic of the individual ports.

It is precisely this cancellation of the traffic (values ​​"IF-MIB :: ifHCInOctets" "IF-MIB :: ifHCOutOctets") that causes the load.

Here is a top excerpt:

last pid: 11414; load averages: 1.63, 1.42, 1.30 up 418+05:36:18 16:13:06
66 processes: 3 running, 63 sleeping
CPU states: 38.0% user, 0.0% nice, 41.5% system, 0.5% interrupt, 20.1% idle
Mem: 986M Active, 81M Inact, 152M Wired, 560M Cache, 112M Buf, 81M Free
Swap:

PID USERNAME THR PRI NICE SIZE RES STATE TIME WCPU COMMAND
1793 root 1 76 0 59772K 38904K RUN 3246.6 30.08% mib2d
1646 root 2 -52 -52 564M 208M select 2637.2 17.14% pfex_junos
1792 root 1 76 0 35796K 25132K select 1214.3 12.45% snmpd
1798 root 1 51 0 41172K 23352K select 518.2H 3.42% pfed
1633 root 1 49 0 64888K 29128K select 334.9H 2.59% chassisd
11407 root 1 42 0 11836K 5572K select 0:00 0.22% sshd

 

vc_cpu.png

 

vc_load.png

 

We collect the values ​​every 10 seconds. We also do this on our older ex4200 switches. We have absolutely no problems with the ex4200.

If I set that we only collect the values ​​for the graphs every 20 seconds, then the load decreases, but we have peaks in the graph every 20 seconds.

 

What could be the problem here? I think we are not the only ones requesting SNMP values, so I hope that one or the other has a tip.

 

Best regards Smiley Happy

5 REPLIES 5
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Re: High load due to SNMP monitoring

Wednesday

Hi ,

 

Good day !

Please attach the RSI from the working and non-working switch in-order to check .

 

Regards ,

Sharanya 

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Solution
Accepted by topic author Apfel19
Wednesday

Re: High load due to SNMP monitoring

Wednesday

Sharanya,

 

Please don't ask people to publicly post RSI files there are way too many details in there that should not be on the open internet.  Ask for the more targeted specific information needed for the issue at hand.

 

Apfel19,

 

Anything less than 5 minute snmp collection is aggressive and certainly under 1 minute collection will put a load on cpu, especially with older devices like the ex4200.  If you need that level of detail in collection talk to your monitoring vendor about grpc support instead of snmp.

 

Steve Puluka BSEET - Juniper Ambassador
IP Architect - DQE Communications Pittsburgh, PA (Metro Ethernet & ISP)
http://puluka.com/home
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Re: High load due to SNMP monitoring

Wednesday
Thx @Sharanya Thx @spuluka Yes, i think the RSI have data inside that is not posted to publicly. @spuluka Thanks for the statement. I thought that the SNMP would ask the CPU quite aggressively, but I didn't really want to believe it, since it works without problems with our ex4200. On closer inspection, however, it could be because our ex4200 only have 24 ports and our 4300 48. Here the CPU load should logically be twice as high. Am I correct? I will take a closer look at grpc. Thanks a lot! Best regards, Apfel19
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Re: High load due to SNMP monitoring

[ Edited ]
Wednesday

Hi apfel19, 

 

I agree with steve, the SNMP polling interval seems to be aggressive. Tweaking the polling interval to a higher value might reduce the CPU load, as the reduction in SNMP requests would drastically reduce the CPU load.


Please mark "accept as solution" if this answers your query. Kudos are appreciated too ! 

 

Regards, 

Sharat

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Re: High load due to SNMP monitoring

Wednesday

Thanks for the confirmation, sharatainapur. Smiley Happy

 

Best regards,

Apfel19