High CPU AP - SNMP PRTG

[stefany_pineda]

Hi, 

I have an issue with APs r310, r600, zf7982 and zf7372

In our environment we have implemented 472 AP, 333 in zone 3.6 ( zf 7982, zf 7372 and others) and 139 AP in zone 5.2 (r310, r600 and others).

All APs are monitored with PRTG- SNMP, recently some APs r310, r600, zf7982 and zf7372 presents on PRTG high CPU 100%, 5-7 clients per radio; we try to access ssh and the connection becomes slow and lose the access, the user experiments intermittence; we reboot, reset and change the firmware, however, the issue persist; but if we replace the AP for another model (r610, r710) the issue dissapear

Is there a configuratión or action that we could do to resolve the problem (high cpu)?

thanks

[Ankush_Chandan]

Hi Stefany,

The problem specified by you is possibly due to high multicast traffic flowing in the network causing the AP CPU to spike. Please look at the top output of the supportinfo file and see if the sirq is high and what is load average on these AP's:

### Top: ###
Mem: 469656K used, 1266332K free, 0K shrd, 0K buff, 0K cached
CPU: 2% usr 4% sys 0% nic 91% idle 0% io 0% irq 2% sirq
Load average: 0.61 0.27 0.14 2/221 11609

Are you using any DNS spoofing tool like Securly ? If yes, we have seen such issues in few school districts due to that. I would encourage you to open a support case for the isolation of the root cause and provide you an appropriate solution.

Regards,

-Ankush

[sagar_kuber]

Hi Stefany,

You need to check if there is any kind of Multicast/broadcast storm hitting the APs VLAN.

Also download the support logs of one or two APs and check ### Top: ### section & SIRQ

Using the below CLI command from SSH, the AP CPU & Memory utilization can be viewed.

Ex:

rkscli: sysinfo
CPU : 0.50%
Memory : 384476 KB (free), 793836 KB (total)
OK
rkscli:

Also refer KBA: https://support.ruckuswireless.com/articles/000003275

[stefany_pineda]

Thanks @sagar_kuber,

I have checked Mullticast in the switch port where AP is connected, i found multicast listener ipv6, but i understand it is a normal traffic. Is there a number for AP model at a certain time which could say "the limit" of multicast.

My AP (zf7982,zf7372,r310,r600), has CPU100%, 5-10 clients, customers percive intermittency, and switch port 4310923 multicast, if i clear counter, i have 13 multicast up to 300 in 5 minutes.

When i replace (zf7982,zf7372,r310,r600) with R610, r710, r320 the CPU is under 50% with 30 -40 clients and similar multicast values.

Thanks