Thanks for your response. WPS isn't an option for me so there is only one way to configure. I actually did a hard reset and connected it to another network. Then I rest it again and reconnected it to my network. At that point, it started working properly. There are no IP reservations that would affect this. I tried disabling the DHCP server instead of Auto, but it made no difference. When it failed, neither the extender nor the laptop was visible on the router. It's working now, so I am going to leave it alone.

mrschwarz wrote

So...I have relatively plain vanilla home network. I have a temp sensor that is too far from the router to keep a reliable connection. I purchased a RE105 repeater a couple of years ago. I set it up as a repeater using the default settings. It worked without a problem up until a few days ago. On 3/18, I received an email from the monitoring service that the sensor was offline. 

 

As a first step, I power cycled the repeater, but it didn't restore the connector. I could connect my laptop to the repeater, but it didn't see the internet and the 'signal' LED wasn't lit. I then performed a hard reset. I set the repeater up using the same parameters as originally done. 

 

Since I did that, when I connect my laptop to my router, I get a duplicate IP error and cannot connect to the internet. I can connected to the '_EXT' network on the repeater without a problem, but when I connect to the router, I get no internet. In addition, the entire network is unstable. Just for fun, I updated to the latest firmware, but nothing changed.

 

Is this a hardware failure? Is there anything I can do to verify or fix this?

  

Try resetting both the router and the repeater to their default settings and then setting them up again from scratch. Make sure that you are setting up the repeater as a repeater and not as an access point, as this could cause issues with IP address conflicts. 
Regards: Pintdd