Integrated hardware encryption acceleration for IPSec VPNs and optional firewall/Intrusion Prevention System (IPS) features.
The first part of the filename designates the hardware platform for which the image is built. c2900-universalk9-mz.spa.157-3.m8.bin
Here’s the breakdown:
This is often where people get confused. c2900-universalk9-mz.spa.157-3.m8.bin