Strange network behaviour

[Zorrro]

Six months ago I bought TP-Link router and when I connected it to my PC I was getting I-Ball interface. So I had to change router ip address and was able to use TP-Link normally. My friend told me that it happens if you used other router in past. After couple of months I bought new PC and have never connected any other router to my PC.

Today my internet connection was disconnected so I tried detecting network type. Usually my connection is PPPOE but today it was Dynamic IP, so I changed my connection type to Dynamic IP and saved it. After few seconds I was connected to internet. But at 192.168.1.1 I was getting D-Link interface which I have never connected to my PC to even old PC. Plus at 192.168.0.1 now I am getting TP-Link interface and I can use it normally.

I checked settings of this D-Link router and found that it has DHCP enabled with around 10 users connected to it. So I assume that someone inexperienced haven't setup their router correctly.

But what I find weird is that I am accessing some external interface on my PC as if it is in my home. Other strange thing is that all users through my isp are on same public ip but when I use this dynamic IP connection I am getting different public ip.

Important thing to note is that I have never connected different router to this pc or I don't have any other router in my home. I find this whole situation strange. Plus my ISP support is poor so I don't have hopes of getting answer from them.

[rproffitt]

The story is unclear but here, my PC connection has not been PPPoE for over a decade. So I take that as just a guess at what's up.

Since you own this router, go ahead and reset it, then give it a new SSID and go for WPA2 and a new password. If there are connections to the Ethernet ports, unplug those that don't belong to you.

Now, are you running Windows 10? If so, do not share WiFi Passwords! Read http://www.cnet.com/how-to/how-to-kill-wi-fi-password-sharing-in-windows-10/

[Zorrro]

Well I figured it out, someone on my ISPs network had their router configured incorrectly or didn't configure at all and left DHCP server on and I was able to login using admin admin so that explains.

About the my router ip changed itself, it happened because LAN and WAN ip were same so my router switched its ip.

1. When the IP address which the WAN port of the router obtains is in the same network segment with the LAN port, the IP address of the router's LAN port will automatically change to a different network segment. For example, the default IP address of LAN port is 192.168.1.1. If the router's WAN port obtains an IP address as 192.168.1.X, the IP address of LAN port will automatically change to 192.168.0.1.
2. If the IP address of the router's LAN port has changed, the router will reset automatically. And the original configurations of the virtual server and DMZ hosting will be lost.

Finally about public ip being different than regular public ip, probably someone bridged two networks together though I don't know much about it.