On 24 September 1993, the IETF published RFC 1519, designating Classless Interdomain Routing (CIDR) and variable length subnet masks as the standard. That particular document is obsoleted by later RFCs, but it’s still a milestone.
Before then, IP addresses were allocated by “classes.” Class A, B, and C addresses were the norm. I’m not going to explain classful addressing, because it’s long obsolete and, on the current Internet, stupid.
What I am going to do is go on a mini-tirade about classful addressing. Because there’s a lot of people out there still teaching classful addressing to newcomers. And then these poor newcomers hit the field, and people like me have to spend our time unteaching them what they so painfully learned.
I fully understand it takes a few years to disseminate knowledge. But textbooks are still being published that claim classful routing is the standard. This is an appalling disservice to the profession.
Yes, CIDR looks hard. But if a new network admin can’t handle CIDR and VLSM, they shouldn’t be administering networks. That’s perhaps the easiest math they’ll need to handle in their career. And the Internet is full of cheat sheets for people who don’t want to bother to do the math.
On this, the 25th anniversary of Classless Inter-Domain Routing, I hereby declare 24 September 1993 CIDRDay, dedicated to stamping out classful addressing. A whole variety of celebrations are appropriate.
First, of course: cider! Cider is obligatory on CIDRDay.
Second, whenever someone who should know better says “Class C,” “Class B,” or “Class A” address? Explain to them the error of their ways, with the minimum amount of force needed to make sure that they never say it again.
If you know someone who’s still teaching that garbage? Yell at them until they promise to stop. If yelling doesn’t work, escalate.
Because frankly, I’m tired of reeducating innocent newcomers who should have been better served by their instructors.Stalk me on social media