Does a router know not to hand out static IP addresses to other devices

dd-wrtdhcprouterstatic-ip

  1. I set a computer on my network to use a Static IP address
  2. Shutdown the computer so its not on and not connected to the network

Question: How does my router know not to hand out that IP address to another device (using DHCP) that accesses the network?

All instructions that I see for understanding static IPs online only involve making changes to the client. It seems like you should need to tell your router/DHCP server not to assign that IP address to anyone else.

Can anyone help me understand this or point me to somewhere that will explain it?

UPDATE: Thanks for the responses. I guess what I've learned is that its better/easier to do DHCP Reservations at the router/DHCP server, instead of trying to do static IP addresses at each machine.

Best Answer

Your router can indeed lease that IP address to another client once the lease expires if your machine is off or disconnected, and doesn't renew it. To guarantee you always get the same IP address, you'll want to make what's called a DHCP Reservation in your router (terminology may vary - see this question for details):

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With DD-WRT firmware, you can find this under the Services section:

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