PowerShell cmdlet: Send Magic Packet

PowerShell cmdlet (module/function) to send a magic packet based on a provided MAC address. Comment-based help included in source-code: Get-Help Send-MagicPacket -Full

Installation and Verification

Downloads are available via my git server (https://git.asifbacchus.dev/asif/ps-cmdlet-wol) and GitHub (https://github.com/asifbacchus/ps-cmdlet-wol). You may verify the cmdlet's integrity using CodeNotary vcn authenticate or by dropping the downloaded script onto their verification webpage at https://verify.codenotary.io. Please always try to verify downloaded scripts and software regardless of the source!

Overview

The function sends two (2) magic packets spaced one (1) second apart. One set of magic packets will be sent per MAC address submitted either directly via the MacAddress parameter or via the pipeline (implicitly or explicitly). Usage examples provided via Get-Help Send-MagicPacket -Examples.

The only mandatory parameter is MacAddress which can be provided directly or via the pipeline either implicitly or explicitly (parameter is in the first position). MacAddress is an array of strings. The actual hex values of the MAC address can be separated with either a ':' or '-'. For example, the following MAC addresses are all valid even within the same command:

Send-MagicPacket '1a:2b:3c:4d:5e:aa', 'a1-b2-c3-d4-e5-bb', '1a:2b-3c:4d-5e-cc'

By default, the magic packet will be sent on the global broadcast address for your current system (e.g. 255.255.255.255) using UDP on the echo port (7). These options can be customized via parameters:

• -BroadcastIP | IP | Address: Broadcast address to use. By default, this is 255.255.255.255 but you really shuold use a subnet specific broadcast address instead (e.g. 192.168.1.255). See Broadcast section for more discussion.
• Port: Allows changing the UDP port over which the magic packet is sent. This is by default port 7 (echo). Port 9 ( discard) is also quite common but any port can be used depending on your particular environment.

The magic packet is constructed as per standards: 6 byte header consisting of '255' (hex:FF) followed by the hex-represented MAC addresses repeated 16 times.

Broadcast considerations

Long ago in a galaxy far away... actually a few decades ago right here on Earth, the easiest way to send Wake-On-Lan ( WOL) packets was simply to use the global IP4 all-subnets broadcast address of 255.255.255.255. Because this generates a lot of un-needed traffic, breaks subnet isolation and can be an attack vector, many routers and switches now block this type of broadcast. Although this remains the default for most WOL applications (including this function), it is vastly more reliable and preferred to use a subnet-specific broadcast address. For example, if you are concerned with computers on your subnet of 192.168.1.0/24 then you would use the broadcast address of 192.168.1.255.

More recently, it has also become somewhat common to use the multicast all-hosts address of 224.0.0.1 when sending WOL packets. If broadcast is not working in your environment, you may want to try this as a possible workaround.

Things become a little more complicated with IP6. There is no concept of 'broadcast' in IP6 and thus, you need to use multicast. I have not extensively tested IP6 WOL since I tend to continue using IP4 for this purpose (all my networks are dual-stack). I would assume the simplest place to start testing would be using the link-local all-nodes address of ff02::1. I suspect this should work especially on Windows networks, but I have not really tested this extensively and could be greatly impacted by switches, routers and even machine specific set-ups.

Pipeline

This function is geared toward pipeline usage. The variable MacAddress is parameterized and used by the function for an array of string objects representing individual MAC addresses. This is consistent with WMIC/CIMv2 output for most NIC queries and allows this function to be easily called using piped output from such a query. To see this, try sending some dummy magic packets to the localhost for all interfaces on the local machine:

# get name, manufacturer and MAC address for connected interfaces and pipe to 
Get-CimInstance -Query "Select * From Win32_NetworkAdapter Where NetConnectionStatus=2" | Select-Object Name, Manufacturer, MacAddress | Send-MagicPacket -IP 127.0.0.1 -Verbose

You will see the function picks up the MacAddress of each object (network interface) and sends a magic packet to 127.0.0.1 on port 7 (echo). This is not at all useful, but demonstrates pipeline usage quite nicely, I think.

Module or Function

This was intended to be used as a simple function that can be integrated into other scripts directly or, more conveniently, loaded as a module and referenced as needed in a variety of use-cases.

Feedback

I coded this pretty quickly for a project I was working on in a small LAN deployment. I also use it pretty routinely in networks of various sizes and over VPN connections and also when I'm too lazy to move from my office to the living room to turn on my media centre. I'm always interested in improvements since I don't code in PowerShell that often and I'm sure this can be vastly improved. Please send any suggestions, bugs, etc. to me by filing an issue.

I hope you find this useful! As indicated by the license, you can use this code for whatever you want in any capacity.