Application scenario of one-to-two and two-to-two VLAN mapping
Figure 64 shows a typical application scenario of one-to-two and two-to-two VLAN mapping. In this scenario, the remote sites of the same VPN must communicate across two SP networks.
Figure 64: Application scenario of one-to-two and two-to-two VLAN mapping
Site 1 and Site 2 are in VLAN 2 and VLAN 3, respectively. The SP 1 network assigns SVLAN 10 to Site 1. The SP 2 network assigns SVLAN 20 to Site 2. When the packet from Site 1 arrives at PE 1, PE 1 tags the packet with SVLAN 10 by using one-to-two VLAN mapping.
When the double-tagged packet from the SP 1 network arrives at the SP 2 network interface, PE 3 processes the packet as follows:
Replaces SVLAN tag 10 with SVLAN tag 20.
Replaces CVLAN tag 2 with CVLAN tag 3.
One-to-two VLAN mapping provides the following benefits:
Enables a customer network to plan its CVLAN assignment without conflicting with SVLANs.
Adds a VLAN tag to a tagged packet and expands the number of available VLANs to 4094 × 4094.
Reduces the stress on the SVLAN resources, which were 4094 VLANs in the SP network before the mapping process was initiated.