[Info-vax] Update to TCP/IP problem with Alpha VMS 8.4

[Johnny Billquist]

On 2012-04-07 02.07, glen herrmannsfeldt wrote:
> Johnny Billquist<bqt at softjar.se>  wrote:
>
> (snip)
>> And yes, the previous poster must have been confused. 127.0.0.0 is not a
>> legal host address, either if you have 127.0.0.0/8 or 127.0.0.0/24. A
>> host part of all zeros or all ones are not allowed.
>
> I once had a sysgen of HP-UX for three ethernet ports running on
> a system with only one. It wasn't happy not to have an address
> for the other ports, so I gave them 127.1.0.1/16 and 127.2.0.1/16,
> and lo0 127.0.0.1/16.
>
> That was before the private addresses were allocated, or at least
> before I knew about them, about 1990. Ran fine that way for many
> years.

The "private" ranges have been around a long time. I don't remember for 
sure about 192.168, or the 172.whatever, but 10.0.0.0/8 have been 
"reserved" for much longer than that. It's the old arpanet, and have 
been reserved and forbidden on the Internet since way before 1990.

> It might be that some systems will accept requests on 127.*.*.* anyway.

Oh, I doubt any system would accept requests to 127.*.*.*, it will be 
one specific address, and it would surprise me if it wasn't the address 
you configured for the interface.

>> But really, 127.0.0.0/24 is also a slight misconfiguration, if anyone is
>> doing that. Not that it will be important enough to make any practical
>> difference...
>
> Well, the allocation was made before CIDR, maybe even before subnets.
> It seems to me that even /30 would work just fine.

That's why the "practical difference" comment. It will work with just 
about anything, but the "proper" network definition is 127.0.0.0/8. It's 
that whole A-class network that was reserved for local use, even though 
it's way too much normally.
I know of one tricky use of it. ntpd defines different type of local 
time references as different addresses on the local network.

And yes, even though we now have CIDR instead of the classes, it's still 
127.0.0.0/8.

	Johnny