A method for selecting a Processing Unit, PU, for traffic analysis from a plurality of PUs (50a, 50b,..., 50z), wherein Ethernet based tunnelled Internet Protocol, IP, traffic comprising an Ethernet based tunnelled IP packet is transmitted from a first network node via an Ethernet tap to a second network node of an IP communications network and the Ethernet based tunnelled IP traffic comprising the Ethernet based tunnelled IP packet is to be copied and the copied Ethernet based tunnelled IP packet is to be redirected in the IP communications network to a selected PU, and wherein the Ethernet tap is connected to the plurality of PUs (50a, 50b,..., 50z) via a device and an Ethernet Switch, the method comprising the steps of: - copying, by the Ethernet tap, the Ethernet based tunnelled IP traffic comprising the Ethernet based tunnelled IP packet transmitted from the first network node, forwarding the copied Ethernet based tunnelled IP packet to the device and forwarding the unamended original Ethernet based tunnelled IP packet to the second node; - receiving, by the device for selecting the PU to which the Ethernet based tunnelled IP traffic is to be redirected, the Ethernet based tunnelled IP traffic comprising the copied Ethernet based tunnelled IP packet transmitted from the first network node, the Ethernet based tunnelled IP packet including a header and a payload, the header containing a destination Ethernet address and the payload containing an inner user IP header of an inner user IP packet, wherein the header of the Ethernet based tunnelled IP packet further includes a first Virtual Local Area Network, VLAN, tag; - receiving, by the device and from each of the plurality of PUs, a second respective VLAN tag, wherein the plurality of PUs are arranged in a plurality of VLANs independent from each other so that the second VLAN tag indicates a logical separation of the plurality of PUs (50a, 50b,..., 50z) into two or more subsets of the plurality of PUs (50a, 50b,..., 50z); - modifying, by the device, the destination Ethernet address and the first VLAN tag contained in the header of the copied Ethernet based tunnelled IP packet on the basis of the inner user IP header, wherein the modified first VLAN tag is selected out of a set of the respective second VLAN tags associated with each PU; - selecting, by the device, the PU for traffic analysis from the plurality of PUs (50a, 50b,..., 50z), wherein the copied Ethernet based tunnelled IP traffic comprising the Ethernet based tunnelled IP packet is to be redirected to the selected PU in accordance with i) the modified destination Ethernet address and ii) the modified first VLAN tag; and - redirecting, by the Ethernet Switch, the copied Ethernet based tunnelled IP traffic comprising the Ethernet based tunnelled IP packet to the selected PU in accordance with i) the modified destination Ethernet address and ii) the modified first VLAN tag, wherein the traffic between the Ethernet Switch and a first one of the plurality of PUs is isolated from the traffic between the Ethernet Switch and any second PU different from the first PU. - copying, by the Ethernet tap, the Ethernet based tunnelled IP traffic comprising the Ethernet based tunnelled IP packet transmitted from the first network node, forwarding the copied Ethernet based tunnelled IP packet to the device and forwarding the unamended original Ethernet based tunnelled IP packet to the second node; - receiving, by the device for selecting the PU to which the Ethernet based tunnelled IP traffic is to be redirected, the Ethernet based tunnelled IP traffic comprising the copied Ethernet based tunnelled IP packet transmitted from the first network node, the Ethernet based tunnelled IP packet including a header and a payload, the header containing a destination Ethernet address and the payload containing an inner user IP header of an inner user IP packet, wherein the header of the Ethernet based tunnelled IP packet further includes a first Virtual Local Area Network, VLAN, tag; - receiving, by the device and from each of the plurality of PUs, a second respective VLAN tag, wherein the plurality of PUs are arranged in a plurality of VLANs independent from each other so that the second VLAN tag indicates a logical separation of the plurality of PUs (50a, 50b,..., 50z) into two or more subsets of the plurality of PUs (50a, 50b,..., 50z); - modifying, by the device, the destination Ethernet address and the first VLAN tag contained in the header of the copied Ethernet based tunnelled IP packet on the basis of the inner user IP header, wherein the modified first VLAN tag is selected out of a set of the respective second VLAN tags associated with each PU; - selecting, by the device, the PU for traffic analysis from the plurality of PUs (50a, 50b,..., 50z), wherein the copied Ethernet based tunnelled IP traffic comprising the Ethernet based tunnelled IP packet is to be redirected to the selected PU in accordance with i) the modified destination Ethernet address and ii) the modified first VLAN tag; and - redirecting, by the Ethernet Switch, the copied Ethernet based tunnelled IP traffic comprising the Ethernet based tunnelled IP packet to the selected PU in accordance with i) the modified destination Ethernet address and ii) the modified first VLAN tag, wherein the traffic between the Ethernet Switch and a first one of the plurality of PUs is isolated from the traffic between the Ethernet Switch and any second PU different from the first PU.