PHP in MPLS

Penultimate Hop Popping is used only for directly connected subnets or aggregate routes.

A few important side details:

1) PHP doesn't work with cell-mode MPLS (each cell needs a VPI/VCI,right?).
2) PHP will strip the TDP/LDP label on the penultimate router, leaving just the VPN label
for the PE to deal with.
3) "PHP" will strip the TE label on the penultimate router OF THE TUNNEL, leaving the
underlying label stack for remaining routers to use*
4) "PHP" will strip the FRR label on the penultimate router OF THE TUNNEL, leaving the
underlying label stack.

You can change this behavior by "mpls ldp explicit-null" command
This command will send label 0 instead of Implicit Null label