Percentage free will vary from one model to another. Even the same models may have different amounts of RAM. For example, the Pix 515 comes with 32MB or 64MB. Other variables affecting RAM usage:
The number of interfaces
The number and length of ACLs, especially with TurboACL
Use of the PDM
Use of stateful failover
The number of free blocks is also very important to a Pix. The pool of blocks are allocated at boot time for connections and translation information. These are important to track as well. You can have 50% free memory and have a problem due to insufficient free blocks for new connections and logging.
I suggest you monitor free blocks and free memory over time. The baseline is dependent on your business. If you sell Christmas trees, the seasons affect your baseline a lot. At least monitor your firewall for a month during a "peak" and "normal" period to establish your own baseline.
From a command line, you can use [show cpu usage], [show mem], [show perfmon] and [show pdm history] to monitor these values. Of course, you can use the PDM to monitor these things as well with a timeline graph.
You can use SNMP to poll the CPU, blocks, and memory utilization if you're running Pix 6.2+. Then you can graph it and perform threshold checks with an NMS. MRTG can graph these things easily for you.
DocumentationCode download linksGoalRequirementLimitationsSupported ISR and UCS-E ModelSupported ISRG2 and UCS-E Blades:Supported ISR4K and UCS-E Blades:Step by Step ConfigurationConfigure one of the connectivity options to access the Cisco IMC from the n...
Firepower Threat Defense (NGFWv) on UCS E-series - Transparent Mode in HA
DocumentationCode download linksGoalRequirementLimitationsSupported ISR and UCS-E ModelSupported ISRG2 and UCS-E Blades:Supported ISR4K and UCS-E Blades:Step by Step ConfigurationCo...
I am currently unable to specify "crypto keyring" command when configuring VPN connection on my cisco 2901 router.
The following licenses have been activated on my router :