Narration: while I bought a top the line router 7-8 years ago, my linksys stops working when I tried to connect to a different port! The symptom is more like this. It broadcasts intranet signal but can not connect to a live ethernet port.
I remember that it happened once and I was able to fix it. Since I did not take a good note, now I have totally forgot and I am back to square zero. Hopefully, I can fix it this time and in the meantime have a thorough documentation. It shall be useful for others, I hope.