6. Carefully Select 40MHz-wide Channels
When using Wireless N gear with the default 20 MHz-wide channels, there is no impact on the channel availability, selection, and interference. You still use the three non-overlapping channels of 1, 6, and 11.
However, if you are using channel bonding and making use of the 40MHz-wide channels, there is a major impact. Because the channel frequency range used by the equipment doubles, it essentially means you now have only one non-overlapping channel in the popular 2.4 GHz band, and nine indoors for the 5GHz band.
Thus you need to carefully select the channels.