You can try to configure your switch via web interface just like the following picture shows: It is very simple to configure NTP or something.

Well, I am afraid there is no way for us to do such kind of configurations.

I don't think it is a problem of TL-ER6120 as you can Ping the LAN IP address of TL-ER6120. The thing is the firewall of all the PCs in the LAN network will block the Ping test. In other word, if you...

What do you mean by "However the clients cannot connect to the 10.11.8.x network automatically". Do you mean you can't ping the LAN IP address of TL-ER6120?

This is my e-mail: ilookhandsome@126.com Please send your problem to my e-mail, maybe I can help you.

Enable DHCP PD Here PD means Prefix delegation which is just delegated mode. Please go to Network -> IPv6 LAN settings, and you can set Address Autoconfiguration Type as RADVD, set Site Prefix...