Clients in same WLAN can't reach each other

Installing and Using OpenWrt Network and Wireless Configuration
72

@RadianM - the way I understood it is the following:

  • there is a little known per-iface option option multicast_to_unicast which - if unset - defaults to true
    • that feature implies mac80211-level client isolation and handles client<>client forwarding using a mechanism called "bridge hairpinning" instead
    • in theory this should not prevent client<>client communication and work the same way as an unisolated wireless network but it seems that - at least on 17.04 - there might be some kernel level issues preventing that from working properly
  • since the multicast_to_unicast option is neither mentioned in the default wifi config, nor exposed in LuCI, users are not aware of it and are unable to disable it (without knowing that it exists + SSH access)
    • the implicitely enabled isolate option is confusing as it is added despite option isolate 0, due to the implicit-enabled-if-absent multicast_to_unicast
  • a workaround is to manually add option multicast_to_unicast 0 to all affected config wifi-iface sections
  • a specific fix has not been added to OpenWrt/LEDE yet
    • for LEDE 17.01.5 a likely fix will be disabling this feature by default + exposing the option in LuCI for users to be to control it
    • for OpenWrt 18.06 and master it needs to be confirmed if there is still an isolation problem

Someone please correct me if the above is wrong.

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