I am on the west coast and I am using Sonic fiber internet (sonic.com). The modem provided by the ISP is Pace modem. I am running Ubuntu.
In the modem configuration, I saw that my public IP is 198.xx.xxx.xx, and when I do "ifconfig" from the shell, my interface wlp3s0 has IP address 172.yy.y.yy.
From outside, I can log into my computer from either address (i.e., from both 198.xx.xxx.xx and 172.yy.y.yy).
My modem has been configured to pass ssh onto my computer. If 198.xxx is the modem's NIC, then is 172.yy my computer's NIC? If 172.yy is my computer's NIC, then shouldn't its address start with 192.168.zz.zz? Shouldn't my computer not have a publicly accessible address other than through the modem's NIC (now it seems 172.yy is my computer's public address)?