Network devices getting an IP address in the 169.254.x.x range?

Question

I'm totally confused by what's happening to my wifi router, so seeking help here.

Configuration

I have a modem/wifi router (Netgear CG3000D—let's call it main) connected to cable and configured with 255.255.255.0 mask. The LAN works fine, I'm getting 192.168.0.xxx IP addresses.

Connected to the router via CAT5 there is another wifi-router, used as a switch and broadcasting another wifi network—255.255.255.0 IP addresses are seen on its LAN ports as well as on the Wi-Fi connections.

On the wifi from the main router I also used to have 192.168.0.xxx IPs via DHCP and everything was working perfectly.

Problem

But all of a sudden at some point my main router decided to switch wifi connections to 255.255.0.0 mask. So now devices connected to this network get IPs of 169.254.x.x and cannot communicate to other devices on the network.

Question

I am totally puzzled by why this happened and also where exactly these settings are. Nothing on the main router seem to be setting this. And I don't think the second switch should be affecting this, but mentioned it to give a fuller picture.

Any ideas where to look at?

Answer 1

Give this a shot . . .

1. power off the machines getting the 169.254.x.x addresses and keep them powered off.

2. Now, unplug the power from your wireless router and wait two minutes with the electrical power disconnected and then plug it back in and let it power up.

3. Wait five minutes and now start up the machine with the issue.

Check the IP assignment on the device connected to the router now and see if things are back to normal.

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The 169.254.x.x Address

Because the 169.254.x.x IP address was the dynamically assigned IP address to this machine, we knew DHCP was having an issue giving it an IP address, and I've seen this many times when routers start acting up like this — and not necessarily just with Windows either.

Automatic Private IP Addressing (APIPA) is a DHCP failover mechanism for local Internet Protocol version 4 (IPv4) networks supported by Microsoft Windows. With APIPA, DHCP clients can obtain IP addresses when DHCP servers are non-functional. APIPA exists in all modern versions of Windows including Windows 10.

When the DHCP process fails, Windows automatically allocates an IP addresses from the private range 169.254.0.1 to 169.254.255.254. Using ARP, clients verify the chosen APIPA address is unique on the network before deciding to use it. Clients then continue checking back with the DHCP server at a periodic interval (usually 5 minutes) and update their addresses automatically when the DHCP server is again able to service requests.

_source

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Reasons

Routers are just like any other device with an OS and circuitry components running on electricity; sometimes they get fragmented memory, etc. and just need to be power cycled to refresh everything for all feature and functions to work properly again when such behavior exists.

Power cycling routers seems to work best while all devices are disconnected from them (wired and wireless); hence, powering them off.

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Further Considerations

You could also look for a firmware update for your router make and model if you continue to have such issues—there could be a bug, memory leak, etc. that's been patched via a newer version of firmware if you continue to have ongoing experiences like this (even if you go days without it but then...).