Modem in bridged mode connects to RT-AX88U - speeds from router are 60% lower - Solved

[fafot]

I just upgraded my internet from cable to fiber. I have 275Mbs from the ISP when I use the modem output and plugging it directly to the laptop. When the modem is setup to bridged mode and connected to the RT-AX88U running Merlin 388.1 firmware, the maximum speed is only 99Mbs.
I am using Cat 7 cable between them.

I have no idea what can cause this steep speed loss. I switched network cables but the problem is not solved. I'm wondering if I have to adjust some settings in the router?

Help will be much appreciated.

 

[glens]

One of the two cables is only able to connect at 100 Mb/s, looks like. Did your cable swaps involve more than just the two?

 

[fafot]

One of the two cables is only able to connect at 100 Mb/s, looks like. Did your cable swaps involve more than just the two?

Actually it was the most silly thing that I did. The cables were cat 7 and cat 8 but... I did not realized that when the Fiber To Premises is installed, the Telco company is already putting a modem. So instead of them telling me this, they asked me to bridge MY Modem. So, what I did is I tried to put it again through another modem that was actually a basic router-modem that while bridging of it is most probably allowing only 100Mbs speed.

Anyway, the real problem nowadays is when talking to support people they don't distinguish between modem and router. They call everything a Modem and because of this I was totally confused. When I called support the second time, the support person on the spot told me about this modem the Telco installed.

Tx for your answer.