topic Cisco ISE server crashing after CPU spike in Network Access Control

Cisco ISE server crashing after CPU spike

BumbleIT — Thu, 19 Feb 2026 13:53:09 GMT

I have a Cisco ISE server that I have built and it has crashed 3 days in a row despite passing all health checks. CPU seems to jump up from 10% to around 80-85% before all services then fail and the server needs rebooted. When it crashed it is not accessible via the web interface or ssh so it needs a hard shutdown and reboot. What might be causing this CPU spikes and what logs would be best to check to see what the cause may be? This is a test ISE servers so no authentications going to it so not much load on the server itself. It is a AWS Instance type C5.4xlarge which is the recommended type for the software. ISE version is 3.4.0.608.

Re: Cisco ISE server crashing after CPU spike

Mark Elsen — Thu, 19 Feb 2026 17:43:18 GMT

- @BumbleIT Use the latest patch release for ISE 3.4 ; if not yet done :
https://software.cisco.com/download/home/283801620/type/283802505/release/3.4%20Patch%203

Re: Cisco ISE server crashing after CPU spike

Y. Yordanov — Fri, 20 Feb 2026 11:39:30 GMT

Useful commands would be tech top just to see which process is spiking.

Thread dump from CLI:
app conf ise - option to generate thread dump

And afterward a support bundle from CLI.

But in any case, it's better to open a TAC case, since there are a lot of things that might be causing that.

Re: Cisco ISE server crashing after CPU spike

BumbleIT — Mon, 23 Feb 2026 08:21:23 GMT

Thank you for the response. They are on the latest patch. I may attempt to build the as v3.5 to see if that resolves the issue.

Re: Cisco ISE server crashing after CPU spike

BumbleIT — Mon, 23 Feb 2026 08:25:41 GMT

Prior to the primary ISE server crashing I found in the logs the error below.

WARNING: Heavy swapping observed on system in last 5 mins.
Heavy swapping can lead to timeouts, poor performance, and instance eviction.

Not sure if related to the link below but it was meant to be resolved by v3.4.
Field Notice: FN74271 - Cisco Identity Services Engine - Operating System Swap Memory Issue May Cause System Instability and Latency Issues - Software Upgrade Recommended - Cisco