Methods of establishing virtual circuits and of providing a virtual private network service through a shared network, and provider edge device for such network

A method of providing a layer 2 virtual private network (VPN) service through a shared network infrastructure comprising a plurality of interconnected provider edge (PE) devices having customer edge (CE) interfaces, wherein some of the CE interfaces are allocated to a layer 2 VPN supporting a plurality of virtual local area networks (VLANs) and are arranged for exchanging tagged data frames with CE devices respectively connected to the PE devices through said CE interfaces, each tagged frame including a VLAN identifier, the method comprising the following steps:

• receiving at least one tagged frame from a CE device at each CE interface allocated to said layer 2 VPN, and learning a correspondence between said CE interface and each VLAN identifier included in said at least one tagged frame;
• detecting whether a pair of CE interfaces allocated to said layer 2 VPN and belonging to two PE devices correspond to a common VLAN identifier;
• and
• in response to such detection, establishing at least one virtual circuit in the shared network infrastructure between said two PE devices, for forwarding frames including said common VLAN identifier.