What labels are encapsulated in the tunnels used by a 6PE deployment?

The inner label is the IPv4 Explicit Null. The outer label is the MPLS transport label,

The inner label is an MPLS transport label. The outer label is the IPv4 Explicit Null.

The inner label is the IPv6 Explicit Null. The outer label is an MPLS transport label.

The inner label is an MPLS transport label. The outer label is the IPv6 Explicit Null.