If you want to set up the LinkIt Smart 7688 as an IoT device, and if you want to use its Ethernet port for the uplink connection, i.e., connection to the main router or to the modem, then this is the setting you will have.

Alternatively if you have an Ethernet only router and want to have an AP (access point) to the router then this is the setting as its name means. OpenWrt keeps a very good document for this setting.

In this mode the device receives its IPv4 address from the main routher through Ethernet port (eth0), while the WiFi (wlan0) creates an AP of its own. Relation between eth0 and wlan0 is direct and transparent to any WiFi devices that are attached to the AP. So the dumb AP.

Let us assume that a subnet 192.160.0.x is created by the main router. When the MT7688 device is connected to the router, it receives an IP address, say 192.168.0.24 through eth0, becomes the address of the lan. This address will be advertised as the address of the AP by wlan0 as well.

Setting up process can be done via LuCI. But here we use uci, whose documentation can be found here. Just follow the procedure here. Followings are the summary.

First change the network protocol for lan to dhcp.

# uci set network.lan.proto=dhcp

Disable and stop dnsmasq service.

# /etc/init.d/dnsmasq disable
# /etc/init.d/dnsmasq stop

We do not need DHCPv6 on lan either. After the change, commit it.

# uci set dhcp.lan.dhcpv6=disabled
# uci set dhcp.lan.ra=disabled
# uci commit

Further disable and stop firewall.

# /etc/init.d/firewall diable
# /etc/init.d/firewall stop

Apply the change and restart network. If necessary reboot the device

# /etc/init.d/network reload

At this point, if you plug the device into the main router. It works as an Ethernet enabled device, while WiFi is disabled by default. Thus it is the desired state as an IoT device with Ethernet.

If you want instead to set it as a AP, then just bring up the wlan0.

# uci set wireless.radio0.disabled=0
# wifi