Clockfort's Tech Blog

I found an undocumented feature in Cisco IOS 11.2.
The command “show interface description” exists in newer versions, so I typed it in out of habit. Even though it doesn’t tab-complete it, or know what that option to the sh int command is, it still works… Albeit badly, and it gives terribly formatted output (All on one line, no spaces between names, no blank spaces where unlabeled ports are, etc)

It still works though! :-)

Makes me wonder how many undocumented features exist in versions of IOS earlier than they are supposedly “released”.


drpepper#sh ver
Cisco Internetwork Operating System Software
IOS (tm) C2900XL Software (C2900XL-HS-M), Version 11.2(8.10)SA6,
MAINTENANCE INTERIM SOFTWARE
Copyright (c) 1986-1902 by cisco Systems, Inc.
Compiled Fri 15-Feb-02 09:47 by devgoyal
Image text-base: 0x00003000, data-base: 0x0020E278
...(rest of output truncated for brevity)
drpepper#sh int ?
FastEthernet FastEthernet IEEE 802.3
Null Null interface
VLAN Switch VLAN Virtual Interface
accounting Show interface accounting
crb Show interface routing/bridging info
irb Show interface routing/bridging info
link-trap Show interface traps on no link


drpepper#sh int desc
Blacktea LinkCSH UplinkJolt ManagementRESNETRESNETRESNETRESNET


I got very bored in a far-too-easy networking class and ended up coding a very memory efficient version of Conway’s Game of Life.
Of note, it uses bit-twiddling/bit-packing to access individual bits on byte-accessible memory for the gameboard, and it uses a sort of buffer-thing to further reduce memory usage, rather than push temporary changes into an entire other temporary game board. I just made it up as I went along. The idea behind being this memory efficient is so that I can plop this on a microcontroller (possibly CSH’s Big Infosys?) and just let ‘er rip on a LED matrix :-)

Source is up at http://github.com/clockfort/Life/