Instructions on how to correctly create wifi extender

Dear All,

What is the correct order to create wifi extender through openwrt, with two frequencies?

  1. Configure Lan to disable DHCP and Firewall service (don't need to change IPV4 IP because it doesn't interfere with default 192.168.1.1)
  2. Connect 5ghz to make client network, and choose wwan

For now the router should have internet, now to transmit

  1. Add new interface (Enabling 2.4 ghz frequency, Access Point and choose lan network, and password, etc)

Does this work by itself, or does it needs relayd to work?

This guide has all the info you need:
https://wiki.openwrt.org/doc/howto/clientmode

It all depends on your goals. You can route traffic without any significant configuration. If you want the clients of the extender to be on the same subnet as the "other" clients, then you'll either need a bridged configuration (such as provided by WDS, or various Layer-2 approaches like GRE tunnels or B.A.T.M.A.N), or the "hack" of relayd or the like for IPv4 traffic. Note that, as far as I know, relayd does not support IPv6.