Headnode Wake-on-lan Support

In a previous post, I mentioned setting up DDNS with NoIP, configuring my router with the DDNS name, and configuring it to forward SSH traffic. This effectively lets me control the headnode, and thus the cluster, from anywhere in the world over SSH. However, I still have to leave the headnode on 24/7 in order to have access to it.

This is where wake-on-lan (wol) comes in. The most common approach is the "magic packet" approach, where a packet with the network adapter's mac address in a certain pattern is sent to the network adapter, thus telling it to wake the computer up. Your network adapter, motherboard, and PSU have to support it to work, which is where my first problem was. The ASUS Z10PE-D8 has two ethernet ports on board, but neither support wake-on-lan. This is not an oversight: ASUS specifically excluded that capability to try to get you to buy their management chip (ASMB8-iKVM), which is fairly expensive, though comes with a bunch of nice remote management features. Since I needed another port for internet anyways, I purchased a 4 port gigabit pcie card (IBM rebrand of Intel i340-t4) that supports wake-on-lan on port 1. After configuring the router and static IP for the new adapter, I could run ethtool (interface name) to examine its wake-on-lan capability. Sure enough, there was a "g" next to wake-on-lan, meaning it supports magic packets. Not all ethernet adapters support wake-on-lan...make sure the one you are planning to buy does before you buy it.

I followed various guides for implementing wake-on-lan. Links: 1 2 3. Originally, it was only meant to be used within a LAN. I found a windows powershell script (there are a bunch, just google them) that creates a magic packet based on the headnode internet interface's MAC address and then broadcasts it to 255.255.255.255. This successfully woke the headnode. However, more work needed to be done to be able to wake-on-lan over the internet.

I created another port forwarding rule ("virtual server" in my router) to forward UDP traffic from an external port to an internal port with the headnode's static IP address. Typical ports for wake on lan are 7 or 9, but I think you can use any. The headnode already has a static IP address, but I also had to create a static ARP assignment in the router, which binds a MAC address to that IP address. I already had DDNS setup with a hostname for my public facing IP. I modified the windows powershell script (on my laptop) to look up the IP address of a given hostname, gave it the cluster's DDNS hostname, changed the port to the external port I forwarded, logged into my VPN so that I would send the wake-on-lan packet from the external internet, and ran the script. Boom, wake-on-lan over internet. I also tested this using the "wake-on-lan" android app when connected to my cell network. There's a wakeonlan linux package, too. Many options to get this to work.

Security disclaimer: opening inbound ports in a router firewall is never without risks. Make sure your computer's firewall rules are setup correctly.