I really could have used such a how-to guide for iOS as with the default UDP443 I was getting constant authentication errors and the AirVPN service was frustratingly unreliable. Only with a bit of digging did I find this thread on the forums which suggested using TCP443 instead of UDP443. This very simple change together with some suggested settings for OpenVPN on iOS has resulted in a VERY stable connection, exactly what I wanted and expected in the first place.
Please note that I am based in the UK and am connecting primarily to the Netherlands servers. Users in other locations may well experience less/more issues than I did.
For more very helpful information about using AirVPN please see this excellent thread by LZ1.
So, to get AirVPN up and running reliably on iOS:
1. Install the free OpenVPN app from the App Store.
2. Use TCP, port 443 when generating config file(s) for iOS from your AirVPN client area (and not UDP, port 443 which is the default).
3. I used the via iTunes method for getting the .ovpn config files from my desktop onto my iPhone where OpenVPN picks them up automatically. There are various other options available.
4. Adjust the OpenVPN settings below as suggested by users SlyFox & Keksjdjdke:
(Note that these settings are only available via the main iOS Settings app as the OpenVPN app has no settings of its own)
- Seamless tunnel (ON) - for those on iOS8 or newer.
- Connect via: any network
- Reconnect on wakeup (ON)
- Protocol: Adaptive
- Compression: Full (the default I think?)
- Connection timeout: None
- Network state detection: Active
- Force AES-CBC ciphersuites: OFF (OFF = better encryption method - AES-256-CBC with HMAC-SHA1 (when ON) vs AES-256-GCM with HMAC-SHA384 (when OFF).
- Google DNS fallback: ON (the default I think but up to the individual user of course)
- Layer 2 reachability: ON
5. Launch the OpenVPN app and connect.
EDIT 03July: updated guide with some extra details.