You won't find this file on a standard Cisco router. Instead, it is used in:
There are three main ways to run Cisco IOS virtually, but IOL (and this specific 2018 build) is often preferred for several reasons: i86bilinuxl3adventerprisek9m21573may2018bin
The i86bilinuxl3adventerprisek9m21573may2018bin image is a powerhouse for networking students. It provides a perfect balance of modern features (IOS 15.7) and high performance, making it the go-to choice for anyone serious about mastering Cisco routing protocols in a virtualized environment. You won't find this file on a standard Cisco router
Indicates this is a 32-bit binary designed to run on Intel x86 architecture. i86bilinuxl3adventerprisek9m21573may2018bin
The build or release date of this specific binary (May 2018).