@Helmut1961 

Hi,

Please check on your AX55 if the Ethernet Status shows 100 Mbps or 1000 Mbps for the LAN port to which you are connected.

If it says 100 Mbps, then in most cases this is caused by an Ethernet cable of insufficient quality. It is very rare that the Ethernet port of a router is defective. Also verify the network adapter of the computer is indeed capable of 1000 Mbps and not limited to 100 Mbps by hardware or software.

  @woozle 

Hi woozle.

Thank you for your reply.

I've checkt this.

All Connected Ports ar 1000 Mbps.

  @Helmut1961 

Any chance there might be "Speed Limits" of 100 Mbps set on the AX55 for the Ethernet client device(s)? I am just asking because it has happened to me before that I set some speed limit and then forgot about it, which later resulted in me wasting time for troubleshooting.
 

  @woozle 

I've changed nothing.
All Ports are on 1000 Mbps Full Duplex.

QoS ist activated with 1000 Mbps.
Is that ok?

Any other suggestions?

  @Helmut1961 

Was the speed via the Ethernet ports always limited to 100 Mbps or have you previously seen higher speeds?

For a test, can you please switch the QoS off and then check if that makes any difference?