GNS3 Cisco IOS Escape Sequence

If you want to use the escape sequence in IOS in order to cancel pending commands (like a ping or a traceroute), using GNS3, and you're trying to use Ctrl+Shift+6 or Ctrl+C or any other combination that is supposed to work, as far as you can tell from the web, then just try Ctrl+6, it will probably work.

Adding comments in GNS3 IOS baseconfig files

If you want to write some comments in your GNS3 baseconfig files for the Cisco IOS, you can use the exclamation mark. It is mainly used for separating commands for easier reading. Everything that is written after the exclamation mark is ignored.

Here's an example: