Common Causes and Solutions for High CPU Utilization Issues
1. IP Unreachables
When an access group denies a packet, the MSFC sends ICMP unreachable messages. This action occurs by default.
2. NAT Translations
NAT utilizes both hardware and software forwarding. The initial establishment of the NAT tranlsations must be done in software and further forwarding is done with hardware. NAT also utilizes the Netflow table (128 KB maximum).
3. Use of CEF FIB Table Space in the Flow Cache Table
4. Optimized ACL Logging.
5. Rate Limit of Packets to the CPU.