DHCP question

[Mr_X1]

Where I used to work, there were devices that needed static ip addresses, such as printers, servers, etc. When I would go into the DHCP console, it showed the pool of ip addresses, but when I clicked on "reservations", it was empty. Now I know that there were obviously a group of ip addresses that were put aside to be used for these devices that needed static ip addresses. In an environment like that, when you need to assign a static ip address for a newly setup network printer, server, etc., you need to know what this list of ip addresses is that are set aside to be used as static ip addresses. You also need to know which of these ip addresses in this list are already taken by current devices and which ones are currently available for use. Where can I find this list of ip addresses that are set aside for use as static ip addresses?

 

[chirkware]

The static IP addresses should be assigned from the IP's that are excluded from the DHCP range. For instance, if your network is on the the 10.1.3.0/24 subnet, and the DHCP range is 10.1.3.100 - 10.1.3.199, the static IP's *should* all be from the address ranges 1-99 and/or 200-254.

Reservations are not for static IP's, but are to guarantee that devices which use DHCP always get a particular IP address (it is "reserved" for the device with the MAC address associated with that reservation). Accomplishes a similar goal as Static IP's, but preserves the flexibility that DHCP affords.

Try out this free utility to map out the IP's on your network:
SoftPerfect Network Scanner: fast and free network scanner

I maintain a spreadsheet of our IP ranges (I have 15 Class C subnets to keep up with), which is critical on our network where almost all devices have static IP's.

 

[Mr_X1]

Thanks for the reply chirkware. This all makes sense now. Although I imagine it would be very difficult for someone taking a job as a network administrator, after the previous network administrator already left before his arrival, to have to search for this information without it being in a centralized location. Or at least in a location where the new admin wouldn't know about, and having to have some sort of network scanner to try to piece this information together.