IP domain
               <-----------------------------------------------

        +======+                                       +======+
        |L3-ID |                                       |L3-ID |
        +======+  /\                           +-----+ +======+
                 /  \       Forward as         |     |
                /IP-A\      per ETH-ID         |IP-1 |      Recognize
Push  ------>  +-+----+         |              +---+-+  <----- ETH-ID
ETH-ID           |         +----+-----+            |
                 |         v          v            |
                 |      +-----+    +-----+         |
                 +------+     |    |     +---------+
        +......+        |ETH-1+----+ETH-2|           +======+
        .L3-ID .        +-----+    +-----+           |L3-ID |
        +======+             +......+                +======+
        |ETH-ID|             .L3-ID .                |ETH-ID|
        +======+             +======+                +------+
                             |ETH-ID|
                             +======+

                          Ethernet domain
                        <---------------->