Tired, headache, too much writing about CIDR, too little sleep. I hadn't realized to what extent netmasks were already a pervasive concept before CIDR; but there weren't netmasks in border routers (or at least not dynamic routing protocols), and there wasn't prefix notation, right?
I taught a Python class again and I dragged in digital roots for some reason -- I couldn't resist. "Hey, what's 37533094858041282253294 % 9? Hey, no paper, now!"
There are some nice memory tricks if you can do various running-total mod n calculations in your head. I saw Arthur Benjamin do one of those once when he performed at UC Berkeley; it was awesome.
Can anybody tell me a good way to get to Santa Rosa from San Francisco on Saturday?