Hi,
For a long time, I was trying to find solution to establish VPN connection between Apple iPhone/iPad devices and Juniper SRX devices, but without success. Now, with latest Apple iOS improvements, and support for IKEv2, it is possible.
In attach, I am uploading document, based on my lab tests, so I hope that some of you, that are using Apple smartphones, will be now able to access your corporate network, behind Juniper SRX devices.
Have in mind, that you should have Apple iOS 9.x installed, and need someone with Apple MAC, in order to prepare Apple VPN profile. More details in attached PDF.
BTW, same VPN profile can be used on Apple Mac computer, at least on MacBook Pro, with ElCapitan OS X (what I tested).
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In short, you do not need now any 3rd party VPN client on your Mac and/or iOS iPhone/iPad (v9.x), if you want to establish IPSec VPN connection with Juniper SRX device.
Marcony