Testing Connection to Servers - New Post

Posts/2021/04/get-live-servers.md

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+---
+post_title: Testing the connection to computers in the Active Directory
+username: tfl@psp.co.uk
+Catagories: PowerShell
+tags: Active Directory, networking
+Summary: How can I get AD computers check to see they are online?
+---
+
+**Q:** As an administrator, I often have to do a lot of reporting on the servers in my domain.
+Is there a simple way to test the connection to every server in my domain or every server or client host in a specific OU?
+
+**A:**  Of course you can do this with PowerShell! You can use the Active Directory cmdlets and `Test-Connection`, although it is not as simple as one might like.
+
+## Using the `ActiveDirectory` module
+
+Microsoft has developed several modules to help you deploy and manage AD in your organisation or via Azure.
+The `ActiveDirectory` module is one which Microsoft ships with Windows Server (although not installed by default).
+You can also load the Remote Server Administration (RSAT) module for AD on a Windows 10 host.
+The RSAT module allows you to manage the AD using PowerShell from a remote machine.
+For more details on the `ActiveDirectory` module, see the [ActiveDirectory](https://docs.microsoft.com/powershell/module/addsadministration/) module documentation.
+
+Use the `Get-ADComputer` account to return details about some or all computers within the AD.
+There are several ways to use `Get-ADComputer` to get just the computer accounts you want with any property you need.
+These include using the **Identity** and **Filter** parameters.  
+Every computer account returned by `Get-ADComputer` contains two important properties: **Name** and **DNSHostName**.
+The **Name** property is the single-label name of the computer (aka the NetBIOS name).
+The **DNSHostName** property is the fully qualified DNS name for the computer.
+Like this:
+
+```powershell-console
+PS> Get-ADComputer -Filter * | Format-Table -Property Name, DNSHostName
+
+Name         DNSHostName
+----         -----------
+COOKHAM1     Cookham1.cookham.net
+win10lt      Win10LT.cookham.net
+cookham24    cookham24.cookham.net
+SLTPC        sltpc.cookham.net
+COOKHAM4LTDC Cookham4LTDC.cookham.net
+```
+
+So you might be tempted to think it simple to test connections to each computer.
+You pipe the output of `Get-ADComputer` to `Test-Connection`, and it just works.
+Sadly, it's not quite so simple.
+
+If you try this, here is what you would see:
+
+```powershell-console
+PS> Get-ADComputer -Filter * | Test-Connection
+Test-Connection: Cannot validate argument on parameter 'TargetName'. The argument is null, empty, or an element of the argument collection contains a null value. Supply a collection that does not contain any null values and then try the command again.
+Test-Connection: Cannot validate argument on parameter 'TargetName'. The argument is null, empty, or an element of the argument collection contains a null value. Supply a collection that does not contain any null values and then try the command again.
+Test-Connection: Cannot validate argument on parameter 'TargetName'. The argument is null, empty, or an element of the argument collection contains a null value. Supply a collection that does not contain any null values and then try the command again.
+Test-Connection: Cannot validate argument on parameter 'TargetName'. The argument is null, empty, or an element of the argument collection contains a null value. Supply a collection that does not contain any null values and then try the command again.
+Test-Connection: Cannot validate argument on parameter 'TargetName'. The argument is null, empty, or an element of the argument collection contains a null value. Supply a collection that does not contain any null values and then try the command again.
+```
+
+What is going on here?
+
+## Property/Parameter misalignment
+
+What we have here is a classic, albeit relatively uncommon, situation.
+The `Test-Connection` cmdlet uses the parameter name **Target** to indicate the computer to which you are testing a connection.
+However, in this pipelined command, the objects produced by `Get-ADComputer` do not contain properties of that name.
+Instead, these objects have properties named **Name** and **DNSHostName**.
+
+[alert type="note" heading="Note"]With Windows PowerShell, you used the parameter **ComputerName** to indicate the computer you are investigating.
+With PowerShell 7, the developers have changed this parameter name to **TargetName**.
+For best compatibility, the cmdlet defines the**`ComputerName** alias to this parameter.
+This cmdlet lets you use either **TargetName** or **Computername** with `Test-Connection`.[/alert]
+
+## ForEach-Object to the rescue
+
+It is pretty easy to get around this parameter/property alignment challenge.
+You use the `Foreach-Object` cmdlet, like this:
+
+```powershell-console
+PS> Get-ADComputer -Filter * | 
+             ForEach-Object {"$_";Test-Connection -TargetName $_.Name;""}
+
+CN=COOKHAM1,OU=Domain Controllers,DC=cookham,DC=net
+   Destination: COOKHAM1
+Ping Source      Address      Latency BufferSize Status
+                                 (ms)        (B)
+---- ------      -------      ------- ---------- ------
+   1 cookham24   10.10.10.9         0         32 Success
+   2 cookham24   10.10.10.9         0         32 Success
+   3 cookham24   10.10.10.9         0         32 Success
+   4 cookham24   10.10.10.9         0         32 Success
+
+CN=win10lt,OU=CookhamHQ,DC=cookham,DC=net
+   Destination: win10lt
+Ping Source      Address          Latency BufferSize Status
+                                     (ms)        (B)
+---- ------      -------          ------- ---------- ------
+   1 cookham24   *                      0         32 DestinationHost…
+   2 cookham24   *                      0         32 DestinationHost…
+   3 cookham24   *                      0         32 DestinationHost…
+   4 cookham24   *                      0         32 DestinationHost…
+
+CN=SLTPC,CN=Computers,DC=cookham,DC=net
+   Destination: SLTPC
+Ping Source      Address                   Latency BufferSize Status
+                                              (ms)        (B)
+|---- ------      -------                   ------- ---------- ------
+   1 cookham24   2a02:8010:6386:0:f810:2b…       1         32 Success
+   2 cookham24   2a02:8010:6386:0:f810:2b…       0         32 Success
+   3 cookham24   2a02:8010:6386:0:f810:2b…       0         32 Success
+   4 cookham24   2a02:8010:6386:0:f810:2b…       3         32 Success
+etc
+```
+
+## Using the Extensible Type System
+
+If you plan to do a lot of this sort of work, there is a more straightforward way to get around this property/parameter alignment issue.
+You can use the Extensible Type System (ETS) to extend any AD Computer object to contain an alias to the `Name` or `DNSHostName` property.
+You define this extension via a small XML file which you then import, like this:
+
+```powershell-console
+PS> Get-Content '.\aaatypes.types.ps1xml'
+<Types>
+ <Type>
+    <Name>Microsoft.ActiveDirectory.Management.ADComputer</Name>
+    <Members>
+       <AliasProperty>
+          <Name>TargetName</Name>
+          <ReferencedMemberName>DNSHostName</ReferencedMemberName>
+         </AliasProperty>
+    </Members>
+  </Type>
+
+</Types>
+
+PS> Update-TypeData -PrependPath .\aaatypes.types.ps1xml
+PS> Get-ADComputer -Identity Cookham1 | Test-Connection
+
+   Destination: Cookham1.cookham.net
+
+Ping Source           Address                   Latency BufferSize Status
+                                                   (ms)        (B)
+---- ------           -------                   ------- ---------- ------
+   1 cookham24        10.10.10.9                      0         32 Success
+   2 cookham24        10.10.10.9                      0         32 Success
+   3 cookham24        10.10.10.9                      0         32 Success
+   4 cookham24        10.10.10.9                      0         32 Success
+```
+
+You can persist this ETS extension by adding the `Update-TypeData` to your PowerShell profile.
+That way, every time you start a PowerShell session, that ETS extension is in place and ready to assist you.
+
+For details of and background to the ETS, see the [Extended Type System Overview](https://docs.microsoft.com/powershell/scripting/developer/ets/overview).
+
+## Summary
+
+The `Get-ADComputer` cmdlet produces objects whose properties the object developers have not aligned, pipeline wise, with `Test-Connection`.
+There is a simple way around that, using `For-EachObject`, although it takes a bit more typing.
+You can also use the ETS to extend the **ADComputer** object to have a more friendly alias.
+
+## Tip of the Hat
+
+This article was based on a request in this blog's issue queue
+See the post [Request - How to get all the alive servers in the domain?](https://github.com/PowerShell/Community-Blog/issues/21)