WoL packets not being sent to NAS connected by 4 port LACP dynamic trunk to 1820-24G switch

[Colin Butcher]

Investigation with Wireshark packet capture and port mirroring shows that WoL packets (UDP port 7 or 9) sent to the ethernet frame broadcast address (ff-ff-ff-ff-ff-ff) are not being sent out of the ports to the attached device when the LACP (dynamic) trunk is down. The individual ports are up (at 10Mpbs FDX) while waiting for WoL packets, but WoL packets are not being sent out of the ports, so the device does not power-up.

With an old 1800-24G switch configured in the equivalent manner with a LACP trunk, the WoL packets are sent out of the ports, which are up at 10 Mbps FDX when the attached device is off, so the attached device powers up successfully. Once up, the ports operate at 1000Mbps FDX, which can be seen in the switch management interface.

The 1810-24G switch appears to behave in the same manner as the newer 1820-24G.

With the 1820-24G switch (and the 1810-24G) the problem appears to be that the switch firmware thinks that the trunk is down, before checking if the individual ports are up, so WoL packets are not transmitted to the ports. With the old 1800-24G, the packets are transmitted out of the ports when the port is up, even though the LACP trunk is down (which is the expected state until the attached device has booted).

Please fix the 1820-24G firmware (and the 1810-24G).

Thanks, Colin.

[Colin Butcher]

Some further information:

WoL packets are sent out of the switch port by reconfiguring the switch to remove the LACP trunk (4 ports), then disabling 3 of the 4 ports that were part of the trunk. The single port that was part of the trunk remains up, so WoL packets are sent out of the port.

Re-enabling the LACP trunk prevents WoL packets being sent out of the ports when the trunk is down but the ports are up at 10Mbps FDX (the NAS is off with WoL enabled).

Layer 2 broadcast ethernet frames (to destination address ff-ff-ff-ff-ff-ff) should always be sent out of a port with state up, even if the upper LACP trunk entity is in state down, otherwise WoL will not work.