L2VPN VC Type 4 Interoperability Between Cisco ASR9000 and IOS XE
L2VPN pseudowire (PW) behavior differs between vendor platforms and device models, particularly around how VLAN tags are handled. Understanding the differences between VC type 4 (VLAN-based) and VC type 5 (Ethernet port-based) pseudowires, and the interoperability gotchas between EVC-based and non-EVC platforms, is critical when building multi-vendor L2VPN networks. L2VPN Packet Structure The basic structure of a packet traversing an L2VPN pseudowire is: Tunnel header + VC label + Control Word + L2 PDU Control Word The control word is a 4-byte field inserted between the VC label and the L2 payload. In Cisco IOS/IOS XR, the control word is enabled by default. ...