Hello Network J
As Andrew has mentioned in his post, the solution to the problem is to use the M-train image c7200-adventerprisek9-mz.152-4.M6. It seems that you are using the S-train image. Now the S-train image does indeed support this command on real hardware, but for some reason, it doesn’t work on GNS3.
This has also been confirmed at this GNS3 forum post.
I hope this has been helpful!
Laz