setup wireguard @ ddwrt

• install latest ddwrt firmware, BS build is recommended
• setup wireguard endpoint by following QuickStart@WireGuard
• add peer config in ddwrt
• add a VAP (wl1.1 192.168.18.1) in Wireless_Basic.asp
• save startup rules to forward traffice from wl1.1 to wireguard oet1 (Administration/Command)

ip rule add from 192.168.18.0/24 lookup 100
ip route add table 100 default via 192.168.2.1 dev oet1
iptables -t nat -A POSTROUTING -s 192.168.18.0/24 -o oet1 -j MASQUERADE

• Services -> Services and ensure that DNSMasq is enabled, in Dnsmasq section, Enter the following Additional DNSMasq Options: dhcp-option=wl1.1,6,8.8.8.8,1.1.1.1

• Setup -> Networking, in DHCPD section add 'Multiple DHCP Server' for VAP interface

Now after your mobile phone connect to VAP, all traffic should forward to wireguard oet1

NOTICE:

• MUST disable AP Isolation for Google home setup
• If something wrong, try to disable SFE(Shortcut Forwarding Engine) @ basic setup.