Does iOS support IPsec IKEv2?

I do not believe the built-in Apple VPN client supports IKEv2 on either the Mac or iOS devices. This is because certainly on the Mac - including Mavericks 10.9.1, and I believe also iOS the VPN client is based on the open-source Racoon software which does not support IKEv2.

There is a Racoon2 see http://www.racoon2.wide.ad.jp/w/ which does support IKEv2 but that is not what Apple include.

Cisco AnyConnect client for iOS and Mac does support IKEv2.

No, IPsec IKEv2 is not supported on iOS by Apple.

The only IPsec that iOS supports is Cisco IPSec (notice that it even has a different capitalisation), according to the link from bmike ♦, the Authentication methods section, iOS basically only supports several IPSec Xauth authentication methods, which are an extension to IKEv1, and are incompatible with IKEv2.

• http://help.apple.com/iosdeployment-vpn/mac/1.2/#app36c9653d

iOS 9 now has a UI for IKEv2 VPN.