There are certain channels in the 5Ghz range that require the access point to do checking to make sure they don't actively interfere with radar... See here for

There are certain channels in the 5Ghz range that require the access point to do checking to make sure they don't actively interfere with radar... See here for a document from Cisco describing the issue: http://www.cisco.com/c/en/us/td/docs/routers/access/3200/software/wireless/3200WirelessConfigGuide/RadioChannelDFS.pdf http://www.cisco.com/c/en/us/td/docs/routers/access/3200/sof... interestingly enough, hard setting the channel to 100 might violate FCC regulations, and DFS should still be used...