A method implemented by a security gateway for supporting per-bearer switching of bearer traffic between a wireless wide area network, WWAN, and a wireless local area network, WLAN, in a manner transparent to the WLAN, the method comprising: establishing, by the security gateway, a secure tunnel through the WLAN to a wireless communication device served over the WWAN by a WWAN base station, based on the WWAN base station sending a message to the wireless communication device to establish the secure tunnel; and forwarding bearer traffic between the wireless communication device and the WWAN base station on a per bearer basis, via the secure tunnel and a connection between the security gateway and the WW AN base station, wherein said establishing comprises, establishing the secure tunnel, based on the WWAN base station authenticating the establishment of the secure tunnel by: receiving, from the wireless communication device, address information of the WWAN base station and further information mapped to security credentials that the wireless communication device and the WWAN base station use for communication over the WWAN; receiving, from the wireless communication device, a request for the security gateway to establish the secure tunnel; responsive to said request, initiating authentication of the secure tunnel establishment towards the WWAN base station using the address information, by sending to the WWAN base station an authentication request that includes said further information; and forwarding authentication signaling between the WWAN base station and the wireless communication device as part of the WWAN base station authenticating the secure tunnel establishment based on said security credentials. establishing, by the security gateway, a secure tunnel through the WLAN to a wireless communication device served over the WWAN by a WWAN base station, based on the WWAN base station sending a message to the wireless communication device to establish the secure tunnel; and forwarding bearer traffic between the wireless communication device and the WWAN base station on a per bearer basis, via the secure tunnel and a connection between the security gateway and the WW AN base station, wherein said establishing comprises, establishing the secure tunnel, based on the WWAN base station authenticating the establishment of the secure tunnel by: receiving, from the wireless communication device, address information of the WWAN base station and further information mapped to security credentials that the wireless communication device and the WWAN base station use for communication over the WWAN; receiving, from the wireless communication device, a request for the security gateway to establish the secure tunnel; responsive to said request, initiating authentication of the secure tunnel establishment towards the WWAN base station using the address information, by sending to the WWAN base station an authentication request that includes said further information; and forwarding authentication signaling between the WWAN base station and the wireless communication device as part of the WWAN base station authenticating the secure tunnel establishment based on said security credentials. receiving, from the wireless communication device, address information of the WWAN base station and further information mapped to security credentials that the wireless communication device and the WWAN base station use for communication over the WWAN; receiving, from the wireless communication device, a request for the security gateway to establish the secure tunnel; responsive to said request, initiating authentication of the secure tunnel establishment towards the WWAN base station using the address information, by sending to the WWAN base station an authentication request that includes said further information; and forwarding authentication signaling between the WWAN base station and the wireless communication device as part of the WWAN base station authenticating the secure tunnel establishment based on said security credentials.