How do masks /32 (255.255.255.255) work?

Question

Computer networks

Actually the question is, I see such a picture at home on my home router, the provider provides access via L2TP. And such an IP with a mask flies to the uplink interface.

Interface, name = "L2TP0"
 id: L2TP0
index: 0
type: L2TP
description: ISP
link: up
connected: yes
state: up
mtu: 1400
tx-queue: 1000
address: 172.16.ххх.хх
mask: 255.255.255.255
uptime: 63810
global: yes
defaultgw: yes
priority: 1000
security-level: public
auth-type: none
remote: 109.ххх.ххх.ххх
uptime: 63810
session-id: 0
fail: no

As can be seen from the output, the interface mask is /32. And what about the subnet address, gateway, host and broadcast? In theory, the mask should be / 30? That is, 4 IPs, and here is one.

Answer 1

The answer in general is PPP.
What is the essence of the mask and default gateway for a normal host? Determine if the destination address is on the local network (that is, the network part of the recipient and sender are the same) and, if the recipient is still "not here", then send the traffic to the "default gateway", and let it figure it out.
In the case of a PPP connection, which is a "pipe", in principle there is no "local network", there is only a certain remote host, and only one, which is located at the other end of the pipe.
On the other side, the router knows in the same way that there is a specific host at the opposite end of a specific pipe, and only one, so it also does not need to bother with masks, that is, we do not have a locale.
So it turns out x.x.x.x / 32 === PPP connection === yyyy / 32, both hosts know who is on the opposite end of the connection, everyone is happy, IP addresses can be distributed regardless of which there is a subscriber in the segment, and there is no need to spend extra IP addresses on the "network address", "gateway address" and "broadcast address".
At the same time, the default route can also be not "to the host", but "to the pipe", and they will figure it out from the other side.