A whole 16 million IPs were allocated in 10.0.0.0/8 for private use, and "10" is pretty easy to remember. Trouble is people then used it.

By the time 192.0.2.0/24, 198.51.100.0/24, and 203.0.113.0/24 were allocated in RFC5737, it was too late.

IPv6 makes human IP addresses meaningless, but even they I believe they allocated 2001:DB8::/32

What a stupid address range for examples

> IPv6 makes human IP addresses meaningless

Tell that to my blog dead:beef:dead:beef:dead:beef:dead:beef

The 10.x region is the reason that a former employer is such a huge user of NAT. They'd acquire a business who were also using that range, and they'd integrate the networks via NAT because it was too hard & dangerous to change the acquired company's devices & services.

Except that everybody knows that the "fake" phone number prefix is 555: https://en.wikipedia.org/wiki/555_(telephone_number) ;-)

Except that 'everybody' in this case only means people in North America, and, reading the siblings of this comment, not even all of them.

Not only people in North America — I’d say everybody that has an above average interest in movies. In Hollywood they use 555-xxxx all the time.

Except these days a real number is commonly used if it provides a marketing benefit, given how easy it is for people to pause movies and read all visible text.

I'm watching Hawaii Five-Oh on Netflix at the moment, and the show regularly uses that prefix when a phone number is required for the plot. Makes me smile every time they do it.

555-1212

Except that not everybody knows that. I use the # for information at stores, when asked for a #, and the cashiers usually have no idea what 555-1212 means. In my sample, the vast majority of people do NOT know.

You might be confusing "do not know" for "do not care."

Yeah, my technique is to punch a random number into the machine, if it works then no problem, but if not the cashier will just scan the "store card" after the 2nd failure.

That's my technique too, but when the cashier asks to look up my number I give them 555-1212. That is what fed into my comment. Most people don't care what number is used, but many also don't know that 555-1212 is the secondary information number. This, of course, depends upon their age and geography. This comes up in the friendly conversations that result upon them looking up the phone number.

When I bought large items at crappy retailers like currys, the often refused to serve me without a postcode. I'd use SW1A 1AA, 2AA or 0AA

Except when buying a TV -- that would be W1A 1AA

Exactly.

Sadly the reverse lookup for 10 Downing Street is "Prime Minister and First Lord of the Treasury".

I told the cashier "That's me, don't you recognise me without the makeup?"

You should have said something like "note that the Chief Mouser to the Cabinet Office, albeit less known to the general public, also lives in the building", which is technically true.

Cashiers don't know, or don't care?

Of course some know but don't care, but the majority I met don't know.

How did you ascertain that they didn't know?

Because I was the one who provided the phone number and stood there talking with them.

How do you differentiate not caring what number you gave them from not knowing? The fact that they showed no reaction is more of a sign of how few fucks are given rather than everyone else's ignorance.

How do you differentiate not caring what number you gave them from not knowing

I said how in the comment to which you replied.

Where did I say, "fact that they showed no reaction"? Why do you interpret something unstated as a fact?

Because you failed to bother to give a more comprehensive answer when I asked how you knew I extrapolated. Did you personally conduct a survey?

Wasn’t 555-1212 the only 555 number that worked?

It used to connect you to directory information (as in "I need to number for mikestew in Seattle...") for the specified area code (or local, if no area code specified). I don't know if it still works or not.

There are other codes in there, caller & circuit id read-backs and other utilities the telco will use. They're usually private, but no serious harm if the public find out about them.

If you make it foolproof, the world will just create better fools.

We haven't always had CIDR.

Saying that not carving a single /24 out of a class A network is bad UX when variable length netmasks weren't even in use yet is a fundamentally silly misreading of history.