Bridge Mode Cable Modem to Archer C7 v2

[cobra98]

It looks like since 1.10 LAN to Cable Modem has a performance problem.
Instead of 400/500 Mbit/s it shows 120 only.
If i upgrade i succeed to reach 190/200, but with direct cable connection i reach 400/500.

Computer has a Gigabit LAN Port, according to the Cable Guys the Modem has a 100 LAN Port.

So what can i do?
Only a normal LAN CAT5 Cable is connected WAN to Cable Modem at the modem. When the internet reached only 200 Mbit/s it worked all fine.
I read going back to old versions for Archer C7 v2 is not recommended below 1.10.
Is it something i can fix too somehow?

[Lantis]

No, your router is at the limits of its CPU.
This has been discussed numerous times, so if you search you can get a more detailed answer.

[cobra98]

Hmm but one thing is strange it was working up to 200/250 before with no problem.
And also Devolo DLAN 1200+ reaches up to 340 Mbit/s.
So i really don`t understand as it has GB LAN Ports.

[Lantis]

The kernel changes and so does the cpu overheads and network stack.
The port speed doesn’t matter, it is about the CPU being able to perform the NAT role at a specific speed.
OEM firmwares use hardware acceleration to solve this.