Hi Huan,
The L2PT for PAGP/LACP/UDLD is only supported in DSBu switches only as 3550/3560/3750 we can also tunnel PaGP/LACP(E Series) and UDLD protocol packets through L2PT.
PAgP, LACP, and UDLD protocol tunneling is only intended to emulate a point-to-point topology. An erroneous configuration that sends tunneled packets to many ports could lead to a network failure.
6500/4500 and even Nexus currently does not support this feature.
HTH
Rahul