169.254.x.x IP Address – Why Network Devices Get This IP Range

dhcpipwireless-networking

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?

Best Answer

Give this a shot . . .

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

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.

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.

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

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.

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...).

Related Solutions

Networking – Who owned 192.168.x.x IP address

It appears that your ISP uses 192.168.1.0/24 for something inside their network. When you are bridged to their network, you see whatever they've setup machines on their network to see. It's possible that someone messed up and these were intended to be private, but it's also possible that they were intended to be reachable by you.

Networking – Troubleshooting Strange IP Address from Router

It looks like you have a new DHCP server on your network.

The first thing you should try and see is which gateway you are assigned, when you are on the bogus subnet. If it is in the range 192.168.1.0/24, you may probably guess on which computer it resides, since you stated your pcs are all on static IPs.

Or, you may try turning off your pcs one by one, and see when your wireless devices, eventually, acquire an IP address in the 192.168.1.0/24 range. The last pc turned off is then the culprit.

Or, you may use a Ubuntu installation (drop an Ubuntu image onto a USB stick, and boot from that)to issue the following commands:

    sudo service network-manager stop
    dhcp -v eth0

from an ethernet-connected pc. The output,

   dhclient -v
   Internet Systems Consortium DHCP Client 4.2.4
   Copyright 2004-2012 Internet Systems Consortium.
   All rights reserved.
   For info, please visit https://www.isc.org/software/dhcp/

   Listening on LPF/eth0/e8:e0:b7:be:72:6a
   Sending on   LPF/eth0/e8:e0:b7:be:72:6a
   Sending on   Socket/fallback
   DHCPDISCOVER on eth0 to 255.255.255.255 port 67 interval 3 (xid=0x333a3d1d)
   DHCPREQUEST of 192.168.73.88 on eth0 to 255.255.255.255 port 67 (xid=0x333a3d1d)
   DHCPOFFER of 192.168.73.88 from 192.168.73.1
   DHCPACK of 192.168.73.88 from 192.168.73.1
   bound to 192.168.73.88 -- renewal in 35456 seconds.

shows this critical line,

  DHCPOFFER of 192.168.73.88 from 192.168.73.1

which displays the IP address of the pc making the offer (192.168.73.1, in my case).

Or, assuming these IP addresses don't mean a thing (i.e., they fall in the 10.0.0.0/8 range), you may try installing a program called nmap, and run it with the command

  nmap -T4 -A 10.55.142.1

where 10.55.142.1 is the gateway your pc is assigned, if it is not 10.55.142.1 please change it to its true value. This will tell you many things about the host pc, including (if you only have Windows machines) its name.

This should at least identify the pc where the new DHCP server is running.