Configure WAN as LAN

/etc/config/network

config interface 'loopback'
  option ifname 'lo'
  option proto 'static'
  option ipaddr '127.0.0.1'
  option netmask '255.0.0.0'
  option ip6assign '60'
  option gateway '192.168.3.1'
  list dns '192.168.3.1'

config globals 'globals'
  option ula_prefix 'fda8:b667:1ed9::/48'

config interface 'lan'
  option type 'bridge'
  option ifname 'eth1.1'
  option proto 'static'
  option ipaddr '192.168.3.3'
  option netmask '255.255.255.0'
  option ip6assign '60'

config switch
  option name 'switch0'
  option reset '1'
  option enable_vlan '1'

config switch_vlan
  option device 'switch0'
  option vlan '1'
  option ports '1 2 3 4 5 0t'