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Convert DHCP Lease to Reservation with Powershell

Scenario :  You have just created (by whatever means) a new server. It has gotten an IP address from DHCP and all is working as it should…..However…. Perhaps this server provides a service that requires a static IP (for whatever reason).

In the old days, you would fire up the DHCP tool from the RSAT tools or <shudder> RDP into your domain controller to convert the dynamic DHCP Lease into a reservation. There is a faster way…… if you guessed Powershell – you are correct 🙂

It took a little spelunking around to work this out but here are the steps to follow.

First, create a remote powershell session to your DHCP server.

 Enter-PSSession -ComputerName MyDC.houndtech.pri 

Next find out the IP address  of the new server. Easy enough with :

Test-NetConnection -computername Newserver.houndtech.pri 

Let’s make things a little easier for later and put that returned object in a variable.

$x = Test-NetConnection -computername Newserver.houndtech.pri  

But we don’t need the whole object, just the IP address, so let’s narrow it down with

$IP = $x.BasicNameResolution.IPaddress  

Now $IP contains JUST the IP address, which is what we need for the next series of cmdlets.
Next we retrieve the DHCP lease object with

 Get-DHCPServerV4Lease -IPAddress $IP 

Finally pipe it to the cmdlet to add the reservation.

 Get-DHCPServerV4Lease -IPAddress $IP | Add-DHCPServerV4Reservation 

Of course this could be piped together into a sweet oneliner that would go well added to any automated provisioning script.

 Get-DHCPServerV4Lease -IPAddress ((Test-NetConnection -ComputerName 'NewServer.HoundTech.pri').RemoteAddress.IPAddressToString)| Add-DhcpServerv4Reservation 

See you next time!

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