I86bi-linux-l2-adventerprisek9-15.2d.bin [2021] -

This makes it perfect for (configuring STP, VLANs) but unsuitable for performance testing (measuring forwarding rates).

Right-click the switch → Idle PC → Let GNS3 calculate the best value. i86bi-linux-l2-adventerprisek9-15.2d.bin

Because this is an x86-compiled Linux process, (like a Catalyst 2960 or 3560). This makes it perfect for (configuring STP, VLANs)