TCL in Cisco Routers

I’d run across the TCL interpreter inside a Cisco router a few years ago and thought “Hmm, that’s cool.  I wonder who’d use that”.  Then, just the other day it hit me:  “There’s a freaking programming language interpreter in the router!”  I did a little googling around there’s a couple of good resources for it, but not very many.

• Cisco’s of course
• Peter Welcher’s site on TCL’ing your router
• Richard Bejtlich’s blog (is there anything the guy doesn’t do?)

I plan on firing up dynamips to see what I can do with it.  Maybe I can write an SMTP server or something.  Or netcat.

If there’s anyone out there who has had experience writing TCL scripts, especially on Cisco gear, let me know. I’d love to learn.