Hi@Lucca_68,

Thank you for contacting our community.

If you're suffering the slow speed issue with the wired adapter, please check the link speed you can get by referring to this link: How to check the associated/link speed on a wired client. Please send here the screenshot with test results.
1. If the link speed is normal, please uninstall the adapter, and reinstall again with the latest driver version.
2. If the link speed is abnormal:
a. Change to another cable (Cat6 or above).
b. Change to plug in a different LAN port on your router.
c. Make sure the router has the same specification, you can test with other devices.

Hi @Lucca_68,

Thank you for your reply.

The actual speed is affected by hardware bottlenecks and configuration issues. First, the built-in network card specification of the ASUS Z87-K motherboard should be 1Gbps. It is recommended that you disable the network card first to eliminate the interference problem of the built-in network card.

In addition, is there a switch between the PC and the Zyxel AX7501-B1? The settings of the switch may also affect the transmission speed.

Tools such as Speedtest are affected by server load, network congestion and latency. It is recommended that you try a few other speedtest servers, other servers might reach better speeds.

Best Regards~