Networking (IP) issues

Please perform the following actions and after each one test to see if the problem is resolved - if so then you can omit the following steps - I have tried to list them in order of increasing effort at least on a Mac and / or an iDevice

1. Check to see if the problem is isolated to one device and if other devices connect normally -
2. If the answer to 1 is "yes" - try to connect the affected device in another location if possible - café or university
3. Please see Apple's recommended settings for Wi-Fi routers and access points
4. Perform a forced restart - this does not delete or purge any data and troubleshoots many issues - here is how - Hold down the Off/On and Home buttons at the same time for about 15-20 seconds until the Apple logo appears. Allow normal boot up.
5. Settings - WiFi - <network name> - Click on forget the network - do a forced restart as per 4 and then add the network again
6. If at home - reboot the router by unplugging for 60 seconds from the AC (mains) and then plug it back in - obviously this step cannot be done in a public place as a café/airport or university. While you are at it - make sure your router is operating on the latest firmware (check manufacturer site)
7. Settings - General - Reset - Reset Network Settings - remember to have WiFi passwords handy since this erases stored WiFi passwords
8. If this is a net new device especially in your home - make sure the router is giving enough DNS numbers to accommodate everything that needs / wants a connection - stuff like the printer, Chromecast get overlooked - ask for details about this if not sure
9. Backup the device to iTunes - Restore as NEW (not from backup) using iTunes - see if problem resolves - if yes - restore backup
10. Make a "Genius" appointment at an Apple Store, or go to another authorized service provider.

Do you have a router behind another router? If your ISP provides you with a gateway or a router and you connect another one downstream of it, you will have two DHCPs active and the behaviour you describe will occur. If so try connecting to the main router only and see if issue still occurs. There are ways of connecting one behind the other.

If not then try the steps on this User Tip:

1) Perform a Forced Restart: Hold down the Home and Wake/Sleep buttons at the same time for about 15-20 seconds until the Apple logo appears. Allow device to restart.

2) Reset Network Settings: Settings > General > Reset > Reset Network Settings. Rejoin the Network again.

3) Reboot Router/Modem: Unplug from power for 2 minutes and plug again. Update Router Firmware (check manufacturer’s support website for a newer FW). Also try different bands (2.4 GHz and 5 GHz) and different bandwidths (20 MHz recommended for the 2.4 band).

4) Change to Google's DNS: Settings > Wi-Fi > Click on the Network, Delete all numbers under DNS and enter 8.8.8.8 or alternatively 8.8.4.4

5) Disable device prioritization on the router if this feature is available.

6) Determine if other Wi-Fi devices on network are working well (other iOS devices, Macs, PCs).

7) Try device at another Network, i.e., neighbors’, public coffee house, etc.

8) Restore the Device (ask for additional for details if desired).

https://support.apple.com/en-us/HT201252

9) Go to an Apple Store for hardware evaluation.

User Tip: https://discussions.apple.com/docs/DOC-9892

The 169.254.x.y email address is a self-assigned email address generated by the phone; it will appear if your router is not assigning IP addresses when the iPhone requests an address from the router. This means that the DHCP server in the router has crashed. You can usually recover from this condition by rebooting the router. It's very a very common problem with consumer-grade routers.