A method for providing an authentication/authorisation of a remote client terminal (100; CL) for use in a network comprising an operator gateway (108; OP GW) and an operator authentication server (110; OP AAA), and an external gateway (112; Corp GW) and an external authentication server (114; Corp AAA), wherein a mutual authentication protocol is agreed between said authentication servers, the method comprising: establishing (200 - 214) a first secured tunnel between the client terminal (100; CL) and the operator gateway (108; OP GW) using an encryption key exchange protocol; authenticating and authorising the client terminal (100; CL) in the operator authentication server (110; OP AAA); initiating a second authentication/authorisation procedure from the client terminal (100; CL) towards the external authentication server (114; Corp AAA) using the first secured tunnel; transforming, in the operator gateway (108; OP GW), at least one message involved in the second authentication/authorisation procedure to be in accordance with said mutual authentication protocol; authenticating and authorising the client terminal (100; CL) in the external authentication server (108; OP GW) (114; Corp AAA); establishing a second tunnel between the operator gateway (108; OP GW) and the external gateway (112; Corp GW) (114; Corp AAA), characterized in that the encryption key exchange protocol is the Internet Key Exchange protocol, whereby the method further comprises: encrypting the messages involved in the second authentication/authorisation procedure, when transmitted between the client terminal (100; CL) (108; OP GW) and the operator authentication server (110; OP AAA), by the established IKE security association, said messages including at least one IKEv2 INFORMATIONAL message exchange with a dedicated payload field for a second authentication/authorisation procedure; and controlling the maintenance of the first secured tunnel and the second secured tunnel in the operator gateway (108; OP GW) such that in response to a removal of the first tunnel, the second tunnel is removed directly. establishing (200 - 214) a first secured tunnel between the client terminal (100; CL) and the operator gateway (108; OP GW) using an encryption key exchange protocol; authenticating and authorising the client terminal (100; CL) in the operator authentication server (110; OP AAA); initiating a second authentication/authorisation procedure from the client terminal (100; CL) towards the external authentication server (114; Corp AAA) using the first secured tunnel; transforming, in the operator gateway (108; OP GW), at least one message involved in the second authentication/authorisation procedure to be in accordance with said mutual authentication protocol; authenticating and authorising the client terminal (100; CL) in the external authentication server (108; OP GW) (114; Corp AAA); establishing a second tunnel between the operator gateway (108; OP GW) and the external gateway (112; Corp GW) (114; Corp AAA), characterized in that the encryption key exchange protocol is the Internet Key Exchange protocol, whereby the method further comprises: encrypting the messages involved in the second authentication/authorisation procedure, when transmitted between the client terminal (100; CL) (108; OP GW) and the operator authentication server (110; OP AAA), by the established IKE security association, said messages including at least one IKEv2 INFORMATIONAL message exchange with a dedicated payload field for a second authentication/authorisation procedure; and controlling the maintenance of the first secured tunnel and the second secured tunnel in the operator gateway (108; OP GW) such that in response to a removal of the first tunnel, the second tunnel is removed directly. encrypting the messages involved in the second authentication/authorisation procedure, when transmitted between the client terminal (100; CL) (108; OP GW) and the operator authentication server (110; OP AAA), by the established IKE security association, said messages including at least one IKEv2 INFORMATIONAL message exchange with a dedicated payload field for a second authentication/authorisation procedure; and controlling the maintenance of the first secured tunnel and the second secured tunnel in the operator gateway (108; OP GW) such that in response to a removal of the first tunnel, the second tunnel is removed directly.