IAP and CPPM AirGroup with high CPU Utilization

[jfox]

I'm trying to track down the cause of this issue and wondering if anyone else has seen anything similar. We're seeing CPU utlization maxed out on an IAP-205 that uses AirGroup.

Background:

Hospitality environment running Instant APs.

We want to allow residents to use personal IoT devices (Chromecasts, FireSticks, Apple TVs, Smart Home Devices, etc.)

Using ClearPass to register resident devices, and Enforcing AirGroup Registration on the IAP, so that Resident A cannot cast to Resident B's devices, and vice versa.

What I'm seeing is occasional high CPU utilization. I belive it is causing clients to drop off.

TFC-Test AP205-cd:1a# show cpu details 
Mem: 91052K used, 34712K free, 0K shrd, 0K buff, 27476K cached
Load average: 2.65 2.73 2.78  (Status: S=sleeping R=running, W=waiting)
  PID USER     STATUS   RSS  PPID %CPU %MEM COMMAND
 2878 root     R       1812  2753 68.8  1.4 mdns
 2816 root     R        752  2753 25.2  0.5 syslogd
    5 root     SW         0     2  2.9  0.0 events/0
10332 root     R <      384 10320  1.9  0.3 top
 2842 root     S N     3600  2753  0.9  2.8 sapd

I also see some errors in logs related to MDNS, but not sure precisely what they mean. Same errors are repeating over and over tens of times per second.

TFC-Test AP205-cd:1a# show log debug 

Dec  6 16:06:34  mdns[2878]: <121019> <ERRS> |AP TFC-Test AP205-cd:1a@10.15.73.64 mdns| |aaa| Received attribute with invalid length -2 in rc_avpair_gen 
Dec  6 16:06:34  mdns[2878]: <527003> <DBUG> |AP TFC-Test AP205-cd:1a@10.15.73.64 mdns|  CPPM mdns_cppm_handle_swarm_coa 1461 Successfully parsed all CPPM attributes using RADIUS library (librc)
Dec  6 16:06:34  mdns[2878]: <121019> <ERRS> |AP TFC-Test AP205-cd:1a@10.15.73.64 mdns| |aaa| Received attribute with invalid length -2 in rc_avpair_gen 
Dec  6 16:06:34  mdns[2878]: <527003> <DBUG> |AP TFC-Test AP205-cd:1a@10.15.73.64 mdns|  CPPM mdns_cppm_handle_swarm_coa 1461 Successfully parsed all CPPM attributes using RADIUS library (librc)
Dec  6 16:06:34  mdns[2878]: <121019> <ERRS> |AP TFC-Test AP205-cd:1a@10.15.73.64 mdns| |aaa| Received attribute with invalid length -2 in rc_avpair_gen 
Dec  6 16:06:34  mdns[2878]: <527003> <DBUG> |AP TFC-Test AP205-cd:1a@10.15.73.64 mdns|  CPPM mdns_cppm_handle_swarm_coa 1461 Successfully parsed all CPPM attributes using RADIUS library (librc)

For reference, this is a proof of concept environment:

One 205 IAP with one SSID. 9 clients all authenticating via mac caching on ClearPass.

The above CLI output was taken with only two AirGroup services enabled (Googlecast and DIAL), and only 3 AirGroup servers online (Chromecast Ultra and Google Home Mini).

Has anyone ran into this before?

[jfox]

I thought I should also add that it's running Instant 6.5.4.8

All AirGroup users and servers are on same SSID and VLAN.

Broadcast filtering: ARP

Multicast transmission optimization: Enabled

Dynamic multicast optimization: Enabled

DMO threshold: 90%