[stripes1776]

Cisco's original IOS is based on the VMS that originally ran on the DEC PDP11/05 at Stanford University. That's where all of the original Cisco founders came from.

OK, it's some flavor of VMS. If I remember correctly, David Cutler invented VMS at DEC. Microsoft later hired Cutler to write Windows NT.

[Knitebane]

Here is a replacement shell for Linux that does the same thing as the Cisco shell. It makes your Linux box look just like a Cisco router. ;)