However, for learning how BGP path selection works, troubleshooting OSPF stub areas, or validating an MPLS L3VPN config, nothing beats its efficiency. It consumes less RAM than a modern web browser and boots in under 10 seconds.
show version You will see output stating: "Cisco IOS Software, Linux Software (I86BI_LINUX-L3-ADVENTERPRISEK9-M), Version 15.5(2)T" The i86bi-linux-l3-adventerprisek9-ms.155-2.t.bin is the Ford F-150 of network simulation. It is not glamorous, it is not new (IOS 15.5 is end-of-life), and it does not support modern features like Segment Routing or EVPN. i86bi-linux-l3-adventerprisek9-ms.155-2.t.bin
Traditional IOS images (like c7200-adventerprisek9-mz.152-4.S.bin ) emulate the entire router hardware—CPU, memory bus, PCI devices, and interfaces—using QEMU or Dynamips. This is slow. However, for learning how BGP path selection works,
As Cisco moves toward IOS XE in CML 2.0, the pure IOL images are slowly fading. But for the home labber running a 2018 laptop, this 15.5(2)T binary remains the most bang for your virtual buck. It is not glamorous, it is not new (IOS 15