CenturyLink DSL modem uses 192.168.0.1 but seeing 172.16.0.1 range. ??

[mchain]

Hi and glad to be a part of this forum.

Recently purchased a new PC with Windows 11 Pro installed.  Also have 3 other machines, one has Windows 11 Home and one has Windows 10 Home and lastly, a Google Chromebook.

Running a CenturyLink C1000A dsl modem and all systems are configured as stand-alone.

Additionally, two other systems are connected to home network: 

• A wireless IP phone
• A Roku TV set

As stated last addition to network was the Win 11 Pro.  During a network scan on the new system, the above private range popped up and online research provided the range:  172.16.0.1 - 172.31.255.255.  The 172. range will change on reboot of the Win 11 Pro system. 

Why does these IPv4 ranges show in network scan and why is it evident in a router running only 192.168.0.1 - 192.168.255.255 IPv4 subset?

And why does 172. IPv4 only show on the new Win 11 Pro system?  And not on the other PC's?

Every scan will show the Win 11 Pro system as some variation of 172.16.0.1 or other server iteration but will not show as currently connected, connection made usually more than 30 minutes prior. 

Is this an outside intrusion?

Thank you.

EDIT:  One additional client is the HP printer configured as wireless.

[pieterh]

Virtual Private Network Client(s).....

this suggests you have  VPN client software/connection active ?
if that's correct then 
1) you have an ip-address that is used on the local network only to connect to the local gateway/router
   you local router assigns you an DHCP address -> this will be the 192.168.0.0/24 subnet
2) you have an IP-address that is used within the VPN tunnel -> this will be the 172.16.0.0/24 subnet
   to communicate with the network on the other side 
   your VPN server assigns you an IP-address 
   the network on the other side may be your corporate network ?
   or you may be connecting to your home router using the VPN client.

so two different subnets can be expected and are both valid