I86bilinuxl3adventerprisek9m21573may2018bin - Portable

Cisco IOL images are proprietary software. They are typically only available to Cisco employees and authorized partners. Ensure you are in compliance with your software license agreements before downloading or using these binaries.

This indicates the "Advanced Enterprise" feature set, including strong encryption (K9) and the full suite of Cisco services. m21573: The specific build/version number. may2018: The release date of this particular bin file. Why Use the "Portable" Version? i86bilinuxl3adventerprisek9m21573may2018bin portable

Uses significantly less RAM than IOSv or CSR1000v images. Cisco IOL images are proprietary software

Supports VRF-lite, MPLS, and complex BGP configurations. BGP) and some switching features.

This is a Layer 3 image, meaning it supports advanced routing protocols (OSPF, EIGRP, BGP) and some switching features.