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I've had a router set up for quite some time and it has been working perfectly. My wife called me to tell me the wireless internet wasn't working and when I came home I saw that my phone was connected to the wireless but there wasn't any internet, even though the wired devices had internet. My router is at 192.168.1.1 and gives out the normal IP addresses that you would expect 192.168.1.xxx. The IP address on my phone though was 10.55.142.7, still in the private network range, but totally nothing that should be assigned by my router. I reset the router, disable and enable dhcp, verified what IP address it should be assigning, but without success. I had another spare router that I wasn't using so I replaced the non-working router with the spare but all the wireless devices are still get the 10.55.142.xxx addresses and no internet connection. So I changed the SSID on my router to make sure someone else wasn't trying to used the same SSID but that didn't changed anything. There are no other router's in my house and nothing I can think of that would try to assign out IP addresses.
The wired connections to the router work just fine, but they all have static IP addresses. So I changed my computer to get an address through DHCP, and it got a 10.55.142.xxx address. If I changed the phone to have a static IP address it works! What is going on! It appears that DHCP isn't working but it can't be the router can it? The router was working and I replaced it with another one with the same results. I'm totally confused on this one.
It sounds like you have a rogue DHCP server on your network. You can try disconnecting devices one by one, or a packet analysis tool like Wireshark. – Bob – 2014-01-21T05:02:18.683