Hi  @Diegodahg,

If the speed is limited to 100M, please note that Archer C20 has 1× 10/100 Mbps WAN Port,4× 10/100 Mbps LAN Ports. The speed should be normal.

Then you can consider a router with a Gigabit Ethernet port or higher, click here

Here are some tips which might improve the speed of your Archer Router:
    1) If Ethernet speed is slower than expected, please try different Ethernet cables (CAT5E or above) on the Router.
    2) Disable QoS, please access http://tplinkwifi.net and go to Advanced >> QoS to disable it.
    3) Disable Parental Control, please go to Advanced >> Parental Control to disable it.
    4) If wireless speed is slower than expected, please go to Advanced >> Wireless Settings to change the 5GHz Wi-Fi channel, you may try different channels to find the best one for your environment.
    5) Disable SIP ALG and UPNP, please go to Advanced >> NAT Forwarding >> UPNP to disable UPNP, go to Advance >> Security to disable SIP ALG.
    6) Try a few other speedtest servers, other servers might reach better speeds.