MPLS push-pop-swap labels
Assuming this is the topology. CE1 is advertising prefix 10.1.1.0/24 and CE2 is 220.127.116.11/24 and they're both communicating each other.
CE1-PE1-P1 - P2 - PE2 - CE2
going back to the MPLS process, unlabeled packet adds label and MPLS routers do the rest of push-pop-swap and send across and stripped off the label as regular IP unlabeled format on the other side.
Let's say Host 10.1.1.100 is communicating to Host 18.104.22.168 and vice versa.
From PE's standpoint, how to determine that host 10.1.1.100 is added a label 10 (for example) ? And I can trace mpls labels from left to right of the topology.