Core Network 
       ^                ^
       |                |
       V                v
  +----------+    +----------+
  |  AGGR1   |    |  AGGR2   |
  +----------+    +----------+
    ^      ^        ^      ^
    |      |        |      |
    |      +-----------+   |
    |               |  |   |
    |      +--------+  |   |
    v      v           v   v 
 +-----------+      +-----------+
 |    R1     |      |    RN     |
 |  Router   | ...  |  Router   |
 +-----------+      +-----------+