Better yet: and obtain a legal copy.
The file vios-adventerprisek9-m.vmdk.spa.156-2.t is . While it clearly attempts to mimic the naming of an IOSv VMDK for version 15.6(2)T, the odd extensions ( .spa , trailing .t ) and non-standard formatting strongly suggest it is a third-party repack, potentially dangerous, or simply a misnamed file. vios-adventerprisek9-m.vmdk.spa.156-2.t
But the official way to obtain such an image is through a with an active service contract. Cisco provides: Better yet: and obtain a legal copy