FIOS gigabit slows down to 100/100 after an hour

Question

It's taken a me a while to troubleshoot to this level, but my problem is that I am paying for gigabit internet, but only getting 100/100 speeds.  After an extended electrical outage, I realized my speed had gone up to close to gigabit levels, but it slowed down after a while.  Troubleshooting has narrowed down the situation:   I have to turn off my router for a few hours, turn it back on and I get about an hour (really more than 30 min, less than 3 hours) of gigabit internet, then back to 100/100.  Turning the ONT on/off does not help.

I have my own ASUS router (RT-AX3000) with an Actiontec Bonded MoCA 2.0

Any thoughts would be appreciated.

gs0b · Accepted Answer

Speed changes from 1,000/1,000 to 100/100 are almost always due to Ethernet link speed negotiation dropping back to 100Mbps.  Check your router's WAN Ethernet link status lights or find the link status in the UI.  If The WAN port has a 100Mbps link speed, you've found the problem.  The cause is most likely a marginal cable or connector.