With iOS 11, Apple has radically reduced access to underlying Unix routines that many networking apps rely on. As many of you have already noticed, it is no longer possible to obtain MAC address on iOS 11. Many folks have already detailed the problem in depth (e.g., https://netanalyzer.helpscoutdocs.com/article/119-mac-addresses-arent-available-under-ios-11) so we won’t go into all the ramifications here.
The one silver lining here is that the entire dev community is working with Apple to try to find a solution and as soon as one is found we will update IP Scanner to take advantage of it.
In the interim, we are in the privileged position of being multi-platform and have therefore implemented a way to transfer discovered MAC addresses from the Mac OS version of IP Scanner over to the iOS version, either through a direct data dump, or incrementally using iCloud sync.
To take advantage of this process, you can use any version of IP Scanner for the Mac. Launch the Mac app, then launch the iOS app. Look for the import option in the Scanner Tools.