Although the Garmin/Jepp website may say that the G1000 generically does support it, it depends upon the version of software in your G1000. I have version 0321.19 [on a DA40], which does not support it.
However, there is a new version 0321.22 which does support this [warranty upgrade if you have 0321.19 or later versions].
May be different on a C172?
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