Once, when I connected to a company's Wi-Fi, I needed to manually set my local IP address to use it. Later, I discovered that my home's auto-configured IP address had reverted to the one I had manually set, which was on a different network segment than my home gateway, causing me to be unable to connect to the internet. I later found that all my auto-configurations had reverted to the IP addresses I had manually set, and even deleting the manually configured SSID didn't change it back. Interesting.