C7100V how to setup simultaneously the 2 bands?

If you visit the support pages:

Support | NETGEAR

you can feed in the model number and find all the documentation for your hardware.

You can find the model number on the label on the device.

 

By the way, it may not matter, but you have posted your message in the section of this community given over to Cable Modems, Routers and DSL Modems. (This is easily done, given Netgear's impenetrable community structure.)

If you need more help, you might get better and quicker replies, and find other answers, over in the appropriate section for your device:

Cable Modems & Routers

No need to repost there, unless you want to – that will just clutter up the place with duplicated messages – but you might find advice related to your hardware.