Sleep Proxy and IP Address Conflicts

I reported this to Apple about their "Resolving IP address conflicts" help page, using the page's Feedback form.

I've repeatedly seen the message "Another device is using this address" when I wake up my MacBook. I had been letting my pfsense firewall issue a DHCP address from the range below 99. Considering the possibility that some random device was accidentally issued the same address during some overlap between sleep times and lease intervals (though I couldn't find it in the arp tables on either the laptop or firewall), I changed the laptop to be a static address in a different range. The message appeared again, with the new address! So this wasn't some coincidence. The newest item in my network is a Time Capsule, and I've been told by a network guru friend that it has a subtle, well-hidden feature called "Sleep Proxy" which is supposed to make life easier.

I spoke to a third-level tech at AppleCare but she unfortunately didn't know anything about Sleep Proxy on Time Capsule.

I suggested to Apple that they:
1) Fix their IP stack to test for a Sleep Proxy event instead of alarming the user about a nasty-sounding, obscure, and actually benign event on the network,
2) Add an explanation of the possibility of Sleep Proxy as a reason for the message.

Originally, I didn't know how to turn off the feature on the Time Capsule, and I didn't know what other device or process is trying to reach the MacBook while it's asleep, which is when the Sleep Proxy would theoretically provide its service. (Actually, I was suspicious that it was the Time Capsule itself looking for its backup client, i.e. the MacBook.) I did eventually find out how to disable it from Apple's article HT3774: Turn off the Mac's Energy Saver preference "Wake for WiFi network access" which registers the Mac with Bonjour Sleep Proxy. I haven't had the message once since I turned that off.

Update 2014-10-05: A complete discussion from 2009-2010 is on Apple's site:  https://discussions.apple.com/thread/2160614