Load balancing and failover between 100Mbit cable modem DSL 6MBit

Since I am dependent on the company on the phone and internet, I have assigned to the Fritzbox each Dect phone both ISDN number as well as a VOIP number. Which does not go is to use two WAN lines, ie one each Fritzbox with cable modem or DSL connection to connect and tell the Fritzbox: "If Internet is not generating a route to the other and use the Fritz box as a gateway". Change manually is not because so get all terminals via DHCP a default gateway, either one or the other Fritzbox.
So I have the DSL Fritzbox replaced by this TP-Link TL-ER6020 Router and the DSL modem, here is now the DHCP server is active (192.168.0.20-200). In two WAN DSL modem to the cable is plugged and it was PPPoE selected data as the connection method with the T-Mobile login. In WAN 1 I plugged the cable to the Fritz box. The Fritz box has the IP address 192.168.1.1 get from me and DHCP turned off, and "Static IP" was the TL-ER6020 for the connection method selected with 192.168.0.3 as the IP address and default gateway for this WAN is the Fritz box, ie 192.168. 1.1, DNS also.
It is important that one is for both WAN ports the correct maximum upstream / downstream rates enters because of load balancing the ratio of rates between the two ports is exactly used for connection control.
Everything's missing is in Advanced -> Load Balancing the "Enable Bandwidth Based Balance Routing" to activate for both ports and you've got not only reliability but also a breakdown of the data volume.

The only thing was, I noticed the lack of daylight saving time is setting. But the latest firmware update fixed the.

I am very satisfied.

Edit: DHCP hosts are not added to the DNS server from the router. Thus an appeal to one's own IP device is not possible via hostname. In Windows it works sometimes because there the NetBIOS protocol is still used, but all other devices, smart TV, NAS, Embedded Web Server, Linux, ... not. Very weak. Had its own DHCP / DNS server on Linux computer Put why.