[ih] The netmask

[Craig Partridge]

On Tue, Jan 7, 2025 at 7:12 AM John Day via Internet-history <
internet-history at elists.isoc.org> wrote:

>
> Prior to CIDR IP addresses were just flat identifiers.
>
>
We routed on the network part from the start.  And while officially the
host part may have been flat, in practice it wasn't.  Everyone in network
operations knew how to read net 10 addresses to figure out which IMP and
port the host was on (and thus who to call if things went wrong).  As I
recall, BBN's (and I think MITs and others) class B addresses used one byte
of the host part for a subnet identifier (my first machine was on
128.89.1.XX -- which was a coax Ethernet hung off the first internal port
of the BBN router in Building 6).

Craig

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