Using a bridged router so that I can set the IP settings directly on the gateway server. We have two such routers for two different IPs (we needed a secondary IP but the ISP only provided it through a new subscription.. I know, right?).
These are internet lines that we're not using anymore after two 20-24 hours downtime periods (ISP's fault) and waiting for the ISP to disable them (it's been two months already).
Last week I checked if the internet was disabled on one router (cable into the laptop and manual settings) and it had lost the bridge setting - happened before, works only on auto-settings. Then I tried the manual settings on the 2nd router and it worked as expected - bridge working.
Then I had the idea to try the public IP of the first router into the second. And it worked without issues. After I checked again to make sure I saw it right, I tried 3 more IPs from the same range (not ours this time, but for as little time as needed to test it worked) and it worked the same way. I could assign almost any public IP to my laptop through the bridged modem.
Isn't this a security issue? Probably a weak configuration issue resulting into a security one.
I thought the public IPs should be tied to the MAC address of the modem or something like that.
Should I report this? This is a major ISP in my country but previous experience showed their high level of incompetence so that I think it's useless telling them.