Over the last week we have been experiencing problems with our ASA 5512. The Firewall has went down 3 times over the past week with no knowledge a to why. In an attempt to diagnose the problem I configured syslog (PRTG) and setup debugging. The device still remains up with traffic passing through it.
Today I received a notification from the syslog which may point to the route cause:
System is low on free memory blocks of size 256 (1 CNT out of 20000 MAX)
I can see from the messages delivered by PRTG
I can see memory utilisation is sitting at 50-54% constantly (Even after configuring Netflow and SNMPv3 recently) - Severity (Error)
CPU remains low at around 10-20% utilisation.
Not sure what the current CPU and memory utilisation is after debugging being turned on but I haven't received any triggers alerting me after a day of debug being switched on.
I am trying to get my head around what could be using the memory blocks of size 256. I can see from the below post the possible cause could be cosmetic. Not entirely sure what the responder meant by that.
https://supportforums.cisco.com/t5/firewalling/system-is-low-on-free-memory-blocks-of-size-2048-0-cnt-out-of/td-p/2961017
The revisions we are currently running:
Cisco Adaptive Security Appliance Software Version 9.8(1)
Device Manager Version 7.8(1)
I understand that our software is outdated and this will be addressed next week as I understand it is vulnerable particularly to CVE-2018-0101. This may also address the problems.
Any suggestions to what could be causing the issues of the memory block being depleted?
