Solved What does this legacy file do?

Browsing my filesystem for a networking question I came upon /etc/networks.

I have never heard of its use. From the header date it pre-dates FreeBSD (nic.ddn.mil).

What in the heck is it? Does anyone use it? I know FreeeBSD uses many methods to achieve the same thing.

Is this legacy cruft or useful?

It looks like it simply defines your network. Doesn't Linux use this scheme? Is this for Linux compatibility?
 
I think (but haven't proven it) that if you delete this file, a few things related to the loopback network will start breaking. That's because 127.0.0.1 typically has no entry in any dynamic (DNS) name or routing service. I know that the getnetent() function is used in a few places, and iterates over all possible networks, including the ones defined in this file.
 
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