How to use static IP and DHCP at same time

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How to use static IP and DHCP at same time

Here's the long and short story. I'm getting 8 static IP addresses from ISP x.x.x.176 to .183. I'd like to setup two servers, a mac mini web server and a windows exchange server on two of the static IP addresses (so I can update the DNS zone records accordingly), and use one of the remaining IP addresses in DHCP with NAT for all other machines.

I figured I could do something like this:

ISP -----> switch -----> Airport (x.x.x.178) DHCP NAT

|-----------> Windows Server (x.x.x.176)

|----------->Mac Mini Server (x.x.x.177)

But I was hoping there was a way to just have the airport do DHCP & NAT and assign the IP addresses out of the range (x.x.x.176 and .177 from the ISP), but it doesn't seem to work that way. I tried manually assigning a static IP address from the ISP to a laptop on the wireless network, and I was unable to reach the internet.

Any ideas? Am I stuck using a switch between the ISP and the Airport? I'm trying to avoid using one of the servers as a DHCP server to keep all the traffic as separate as possible.

Thanks!

OS X Server

Posted on Aug 14, 2015 7:10 AM

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Answer 1

Aug 14, 2015 8:12 AM in response to CzarB

If you didn't specifically set up the Airport to do DHCP it will probably have detected that there is an incoming IP number and set it to Bridge Mode - passing through the IP number allocated to it.

Open Applications/Utilities/Airport Utility. Click the image of your Airport and in the pop-up pane click ‘Edit’. In the pane which drops down, click the ‘Network’ tab. Set ‘Router Mode’ to ‘DHCP’ and click ‘Update’; wait for your AE to restart. This should result in the Airport issuing its own IP numbers within the range allowed for LANs.

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Answer 2

CzarB Author

Level 1

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Aug 14, 2015 8:25 AM in response to Roger Wilmut1

It didn't work. The airport was trying to assign IP addresses in the range x.x.x.177 to .183, but I need the NAT because I have more than 5 devices that want to connect to the internet at a time.

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Answer 3

Aug 14, 2015 8:28 AM in response to CzarB

Try 'DHCP and NAT'. I would have expected the Airport to issue numbers in the range 192... which is reserved for LAN use.

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Answer 4

Drew Reece

Level 6

10,684 points

Aug 14, 2015 8:45 AM in response to CzarB

The final addresses in your range are irrelevant to us, we need to know if you are using private LAN ranges or public ones.

Assuming you are using NAT & a private range (192.x.x.x, 10.x.x.x, 172.16-31.x.x)…

OS X has the network setting to assign a static address via DHCP. This means the device will request that address & use it if it is free. Simply change the network interface to use DHCP & set the preferred address.

I think Windows has a similar setting too.

The addresses will need to be in the same range as the router assigns.

Another option is to use the router to receiver addresses for those machines - it is generally safer to do that if you can do so because there is only one place to make the changes instead of at each client.

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