Removing MPLS Labels from Incoming Packets

The JUNOS software can forward only IPv4 packets to a Monitoring Services, Adaptive Services, or MultiServices PIC. IPv4 packets with MPLS labels cannot be forwarded to a monitoring PIC. By default, if packets with MPLS labels are forwarded to the monitoring PIC, they are discarded. To monitor packets with MPLS labels, you must remove the MPLS labels as the packets arrive on the interface.

You can remove up to two MPLS labels from an incoming packet by including the pop-all-labels statement at the [edit interfaces interface-name (atm-options | fastether-options | gigether-options | sonet-options) mpls] hierarchy level:

By default, the pop-all-labels statement takes effect for incoming packets with one or two labels. You can specify the number of MPLS labels that an incoming packet must have for the pop-all-labels statement to take effect by including the required-depth statement at the [edit interfaces interface-name (atm-options | fastether-options | gigether-options | sonet-options) mpls pop-all-labels] hierarchy level:

The required depth can be 1, 2, or [ 1 2 ]. If you include the required-depth 1 statement, the pop-all-labels statement takes effect for incoming packets with one label only. If you include the required-depth 2 statement, the pop-all-labels statement takes effect for incoming packets with two labels only. If you include the required-depth [ 1 2 ] statement, the pop-all-labels statement takes effect for incoming packets with one or two labels. A required depth of [ 1 2 ] is equivalent to the default behavior of the pop-all-labels statement.

When you remove MPLS labels from incoming packets, note the following:

• The pop-all-labels statement has no effect on IP packets with three or more MPLS labels.
• When you enable MPLS label removal, you must configure all ports on a PIC with the same label popping mode and required depth.
• You use the pop-all-labels statement to enable passive monitoring applications, not active monitoring.
• You cannot apply MPLS filters or accounting to the MPLS labels because the labels are removed as soon as the packet arrives on the interface.
• On ATM2 interfaces, you must use a label value greater than 4095, because the lower range of MPLS labels is reserved for label-switched interface (LSI) and virtual private LAN service (VPLS) support. For more information, see the JUNOS VPNs Configuration Guide.
• The following ATM encapsulation types are not supported on interfaces with MPLS label removal:
  • atm-ccc-cell-relay
  • atm-ccc-vc-mux
  • atm-mlppp-llc
  • atm-tcc-snap
  • atm-tcc-vc-mux
  • ether-over-atm-llc
  • ether-vpls-over-atm-llc

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