Why WOL is not working with Dynamic Link Aggregation (LACP) on Synology NAS and Zyxel switch?

JasonTsai

Note: The Synology NAS supports the Wake On-LAN (WOL) feature.

First, you may need to understand the LACP behavior.
If two devices want to build a link via LACP, they exchange LACP packets to confirm each other's status when connected.
If they receive the LACP packet form each other, the port status will change to "forwarding" and then start to transfer packets. It means the LACP function is working.
If the device doesn't receive any LACP packet, it will consider there is no LACP neighbor, and set the port status to "blocking", which means the port doesn't forward the packet.

In this case, although the NAS and the switch support LACP, when the NAS is offline, it will not send any packet out. The switch doesn't receive LACP packets from the NAS, so the switch will consider that LACP doesn't work anymore, and change the port status to "blocking".
The port which is "blocking" will not send any packets out, so that the switch can't wake up the NAS.
It is a normal behavior of LACP, so we consider that LACP is not suitable to use with WOL.

We have studied the Synology NAS and confirmed the function's behavior.
If you want to load sharing by 2 Gbit/s links and use WOL, you only have to set up two links between the NAS and the switch which is configured Static Link Aggregation.
The NAS changes the link aggregation mode to "Balance XOR" (as the following screen) and will work.