why is it so ?

[royarcher]

I have 50 mbps and tests usually come up with that speed most of the time . I have an rt ac 88 u wired to an arris Modem running merlin,of course,now every now and then the speed drops to around 8 or 9 mbps but if I disconnect the wan cable from either the router or modem then plug it straight in again it goes back to 50 mbps straight away.
The cable I am using is cat 7 and it's a 10 meter cable as the router is in the lounge room and the gateway is in the bedroom.
Why does this happen,I mean it's not much of a problem as it may only happen once a week to once a month but I am just curious as to what's going on here.??? I am in Australia so we have nbn if that makes any difference.

 

[L&LD]

What kind of ISP is NBN? Cable, satellite, Fibre, DSL, other?

Have you tested with a quality Cat5e cable instead of that non-official Cat7? For 30' and 50Mbps capabilities, any quality cable will work.

Are you using Ports 5-8 on that RT-AC88U? If you are, can you test with an 8 Port GbE switch instead (and not use Ports 5-8)?

What firmware is the RT-AC88U running? What features, options, and scripts, past the defaults?

When the speed drops, what does the router report the connection speed to be on that Port?

Does rebooting the router affect this issue?

 

[Invisible Boy]

If replug the cable fixes the issue, clean all ports/jacks and see if the problem comes back. My previous ADSL would stop working every few months. I cleaned the modem's WAN jack and it would work for another few months so I just kept doing it until I upgraded.