[OpenWrt Wiki] Switch documentation
openwrt.org › docs › guide-userAug 02, 2021 · Different routers have different switch layouts, so look at the Wiki for your specific device. The TP-Link Archer C7 has eth0 = WAN, and eth1 = LAN (the 4 switch ports). Port 0 of the switch = eth1 (labelled CPU in Luci), Port 6 = eth0. Port 1 is labelled WAN in Luci. Look at the wiki for your router. Every router is different.
[OpenWrt Wiki] LuCI essentials
openwrt.org › docs › guide-userThe OpenWrt full releases, such as the current 18.06.x series, ship with the LuCI WebUI installed. But for lower-memory devices, such as those with 4MBytes Flash and/or 32MBytes of RAM, the full install may fail because of lacking sufficient Flash memory so you will have to build your own imagewith LuCI included.