Before learning how to use it, you must understand what it is. Cisco uses a strict naming convention for its IOS binaries. Let's break down i86bi-linux-l3-adventerprisek9-15.4.1t.bin :
i86bi-linux-l3-adventerprisek9-15.4.1t.bin IOS on Unix (IOU) image specifically designed for routing simulation within virtual lab environments like Core Specifications i86 (Intel/AMD x86 architecture) running on Linux. i86bi-linux-l3-adventerprisek9-15.4.1t.bin