Cisco Cisco IOS Software Release 12.2(33)SRE

For the Cisco 7600 series router, see the following documents for prerequisites:

Configuring PFC3BXL and PFC3B Mode Multiprotocol Label Switching

Configuring Multiprotocol Label Switching on the Optical Services Modules

This feature is supported only on the Cisco 7600 series router in Cisco IOS Release 12.2(33)SRA and 
later releases.. For the Cisco 7600 series router, see the following documents for restrictions:

Configuring PFC3BXL and PFC3B Mode Multiprotocol Label Switching

Configuring Multiprotocol Label Switching on the Optical Services Modules

This feature allows you to specify the path that Any Transport over MPLS (AToM) traffic uses. You can 
specify either a Multiprotocol Label Switching (MPLS) Traffic Engineering tunnel or a destination IP 
address and Domain Name System (DNS) name. If the specified path is unreachable, you can specify 
that the virtual circuits (VCs) should use the default path, which is the path that MPLS Label Distribution 
Protocol (LDP) used for signaling. This option is enabled by default; you must explicitly disable it. 

You configure tunnel selection when you set up a pseudowire class. You enable tunnel selection with the 
preferred-path command. Then you apply the pseudowire class to an interface that has been configured 
to transport AToM packets. 

The following guidelines provide more information about configuring tunnel selection:

The preferred-path command is available only if the pseudowire encapsulation type is MPLS. 

This feature is enabled when you exit from pseudowire submode.

The selected path should be a label switched path (LSP) destined to the peer PE router. 

The selected tunnel must be an MPLS TE tunnel.

If you select a tunnel, the tunnel tailend must be on the remote provider edge (PE) router.