Hello, I have an issue: every 2-3 days my network keeps drooping from 1000mb to 100, if i remove the ethernet cable and put it back will work again for a couple of days. on my phone (wireless) when this happens i checked and i have like 300mb ( that's the max my phone can handle) so i don't think is the router problem. the cable is like 5-6 years old, may i need to replace it or it can be a motherboard issue ?

When one wire is missing 1000 degrades to 100. Could be cable, could be port, anywhere along the way, computer, switch, router. I had this problem once when one pin inside the port got bent so it didn't align with the plug. I have also had ports go bad on a switch or router, I just tape them up and use another.