Operation Manual – VLAN-VPNH3C S3100-52P Ethernet Switch Chapter 1 VLAN-VPN Configuration1-2Destination MAC address0 31DataSource MAC address15Inner VLAN TagOuter VLAN TagFigure 1-2 Structure of packets with double-layer VLAN tagsCompared with MPLS-based Layer 2 VPN, VLAN-VPN has the following features:z It provides Layer 2 VPN tunnels that are simpler.z VLAN-VPN can be implemented through manual configuration. That is, signalingprotocol-related configuration is not needed.The VLAN-VPN feature provides you with the following benefits:z Saves public network VLAN ID resource.z You can have VLAN IDs of your own, which is independent of public networkVLAN IDs.z Provides simple Layer 2 VPN solutions for small-sized MANs or intranets.1.1.2 Implementation of VLAN-VPNWith the VLAN-VPN feature enabled, no matter whether or not a received packetalready carries a VLAN tag, the switch will tag the received packet with the defaultVLAN tag of the receiving port and add the source MAC address to the MAC addresstable of the default VLAN. When a packet reaches a VLAN-VPN-enabled port:z If the packet already carries a VLAN tag, the packet becomes a dual-taggedpacket.z Otherwise, the packet becomes a packet carrying the default VLAN tag of the port.1.1.3 Configuring the TPID for VLAN-VPN PacketsA VLAN tag uses the tag protocol identifier (TPID) field to identify the protocol type ofthe tag. The value of this field is 0x8100 for IEEE 802.1Q.Figure 1-3 illustrates the structure of the IEEE 802.1Q VLAN tag in an Ethernet frame.Figure 1-3 The structure of the VLAN tag in an Ethernet frame
