@TPLDem Well it's been less than an hour and it's already throttled.  The CPU looks nominal, however, so there appear to be 2 problems here. :P

Plz help. :P

Alright so after some digging it appears that the port in question has its speed go from `1000M` to `100M`.  No reboot is necessary.  Simply disconnecting it and reconnecting it resets it to 1000M.  However over time it appears to downgrade to 100M.

  @TPLDem 

If it automatically changes from 1000M to 100M, it may be a faulty cable that had to handshake lower due to errors/noise. I would suggest trying different cables for that port to confirm.

The CPU usage you are seeing may be normal if you have IP statistics enabled. Check and turn that off if you want really low idle cpu usage in general.

There could be actual hardware or software issues but these are some things to eliminate first.

Thank you for the reply @dsj.  I am not so sure on the cable, but one thing I noticed is that the router it went to (also a TPLink router) had an older firmware version.  So I applied that and we'll see how it does.  After a reboot it went back up to 1000M on the ER605.

Note that I have never seen it degrade and then improve.  It has always degraded and stayed there.  However, if it does persist after this firmware/reboot I will look into the cables.

As for the IP Statistics, are you able to point me in the direction of this?  I, unfortunately, do not see this in the ER605 Menu (still finding my way around).  Note that I did not install/configure anything with this router with the exception of the firmware.

Thank you for any continued assistance you can provide.

Dang you might be right after all @dsj ... still drops even after latest firmware and reboot.  I have a 50ft wire between the two wires plus a 4ft + coupler between the two.  Just switched out the wire but wondering if the coupler might be a problem.

What's strange here is that the speed is great after first plugging in and is that way for some time after it.  It's about an hour or so after the cable is connected that it goes down.  Additionally, it just takes a reconnect to also make it snap back up.  It would seem that if it were a cable issue that the connection would be spotty even after reconnecting.

Hm bummer, I've replaced cords and couplers and the problem still persists.  The uplink reports 1000M on plugin and after a while it degrades to 100M.

I can also verify that plugging this same coupled cable directly into the cable modem results in consistent 1000M connectivity.

So the problem does appear to be w/ this router unit.  

Any additional suggestions would be appreciated.

I can confirm that after a day of being plugged in directly to the cable modem that 1000M is maintained without degradation or issue. 

Is there a setting on the ER605 that I should further look into?

  @TPLDem 

Since you're on latest firmware, you could change the port config to 1000M instead of leaving it on auto as an attempt to have it stick.

You might want to look up specs for the coupler or try to eliminate it. Most of them tend to be pretty low spec/quality.