VPN 1                       VPN 2
          +------------------------+   +------------------------+
         /                        /   /                        /
        / S1C_[VN3]..........    /   /                        /
       /         \          :   /   / S2A_[VN1]____[VN3]_S2B /
      /           \         :  /   /        *        *      /
     /             \        :............ * ....     *     /
    / S1B_[VN2]____[VN1]_S1A /   /       *     :     *    /
   +---------:-------:------+   +-------*------:-----*---+
             :        :      * * *  * *        :     *
             :         :   *                   :     *
   Site-1A   :  +-------:-*--------------------:-----*-----+ Site-1C
     [CE1]___:_/_______[N1]___________________[N2]___*____/__[CE3]
             :/       / / \             _____//      *   /
   [CE5]_____:_______/ /    \     _____/     /     *    /
 Site-2A    /:        /       \  /          /    *     /
           / :                [N5]         /   *      /
          /   :     /       __/ \__       /  *       /
         /     :   /    ___/       \__   / *        /
Site-1B /       : / ___/              \ /*         /  Site-2B
[CE2]__/________[N4]__________________[N3]________/____[CE4]
      /                                          /
     +------------------------------------------+
                                   L3 Topology

   Legend:
      N:   Node   
      VN:  VPN Node  
      S:   Site  
      CE:  Customer Edge
      __   Link within a network layer
      :    Mapping between VPN 1 service topology and L3 topology
      *    Mapping between VPN 2 service topology and L3 topology