This specific binary is a favorite for use in GNS3 and EVE-NG because of its low resource footprint. Unlike full VM-based images (like IOSv), IOL images run as simple Linux processes, allowing you to run dozens of instances on modest hardware. Technical Requirements
15.5(2)T does not support modern TLS 1.3, advanced MACsec, or newer IKEv2 cipher suites. Do use this for production—it is strictly a study tool. I86bi-linux-l3-adventerprisek9-ms.155-2.t.bin
Since the image is a 32-bit binary, your Linux host (or GNS3 VM) needs 32-bit architecture support enabled. Run sudo dpkg --add-architecture i386 and install gns3-iou or equivalent packages. This specific binary is a favorite for use
The I86bi-linux-l3-adventerprisek9-ms.155-2.t.bin is one of the most popular IOL images for . I86bi-linux-l3-adventerprisek9-ms.155-2.t.bin