If you have an Apple Airport wireless router, and at some point you set a fixed IP address for your Apple computer under the Network Settings > Ethernet > Advanced > TCP/IP > Configure iPv4 dropdown menu (Manual) and then later return the setting to Using DHCP, the Ethernet port on your computer might stop working properly, and the computer may continue to request the fixed IP address even though you’ve set it to DHCP.
Follow these instructions to fix the problem:
- Begin by setting your computer Ethernet to use DHCP. This is found under under the Apple Menu > System Preferences > Network Settings > Ethernet > Advanced > TCP/IP > Configure iPv4 dropdown menu. Choose DHCP and save/apply.
- Run the Airport Utility (found under Applications > Utilities).
- Your Airport router should show up. Left click once on the icon to display the settings and then click on Edit.
- Click on the Network menu option.
- Click the Plus symbol below the DHCP Reservations list.
- Enter a Description (your computer name).
- Select Reserved Address By using MAC Address.
- Enter your Ethernet MAC address. It is found by going to Apple Menu > System Preferences > Network > Ethernet > Advanced > Hardware. Copy (highlight/select) the number/letter sequence displayed next to MAC Address and paste that into the entry for MAC Address in the Airport Utility.
- Enter an IPv4 Address such as 10.0.1.50.
- This will cause the Airport router to override any previous setting that was requested by your computer or device.
- It’s likely that the previous reservation was somehow preserved in the router and this will fix the problem.
- Just as in this example, the last number should be a higher number because the lower numbers are automatically issued first starting with 10.0.1.2, 10.0.1.3, and so on, as wireless devices join the network. This numbering scheme is based on the default IPv4 addresses for the router. Other routers use 192.168.0.1 or 192.168.1.1 for the router address (gateway).
- When you restart your computer, this new IP address specified in step #9 above will be automatically issued by the router based on the MAC Address of your computer.
- This new IP address will supersede whatever had previously been configured.
- You can now go back into the Airport Utility, following steps 1-9 above. This time, select your computer in the DHCP Reservations list (step #5) and press the minus key to remove this IP reservation.
- Restart your computer. It will probably get the same IP address as it had been issued above. Routers will typically reserve an IP address temporarily for a device until a certain amount of time has passed.