“SoHo” devices come with a default configuration with ether1 as WAN and all other ports as LAN. (this is what you have and that causes the behaviour you reported).
Professional devices usually ship with no configuration, maybe the CCR2116 is an exception and has one or maybe this has changed with some new version/release of either the RoS or of the device.
Good find, adding this to #22:
http://forum.mikrotik.com/t/gp-csa-for-mikrotik-devices/182176/1