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16-23
ATM Switch Router Software Configuration Guide
OL-7396-01
Chapter 16 Configuring Tag Switching and MPLS
MPLS Overview
• BVI cannot be MPLS enabled.
• BVI cannot be VRF enabled.
• Statistics at label level are not supported.
• Layer 2 statistics or Layer 3 statistics for ATM interface are not supported.
• When using the mpls-forwarding command to link a Fast Ethernet module with shared CAM
(content addressable memory) to an ATM router module you can only configure the “master” port
(not the “slave” ports) of the Ethernet processor interface. However, once the configuration is
applied to the master port the controlling ATM router module performs MPLS and VRF processing
for all ports controlled by the Ethernet processor interface (master and slave ports).
Note There is one master port per Ethernet processor interface (which controls four Fast Ethernet
interfaces). For example, on an Ethernet processor interface controlling Fast Ethernet
interfaces 2/0/0 through 2/0/3, Fast Ethernet interface 2/0/3 is the master port.
MPLS/Tag Switching Terminology
Table 16-9 provides a conversion from the tag switching designations to the equivalent MPLS
designations.
From an historical and functional standpoint, Label Distribution Protocol (LDP) is a superset of the
pre-standard Cisco Tag Distribution Protocol (TDP), which also supports MPLS forwarding along
normally routed paths. For those features that LDP and TDP share in common, the pattern of protocol
Table 16-9 Equivalency Table for Tag Switching and MPLS Terms
Old Tag Switching Terminology New MPLS IETF Terminology
Tag switching MPLS (Multiprotocol Label Switching)
Tag (short for tag switching) MPLS
Tag (item or packet) Label
TDP (Tag Distribution Protocol) LDP (Label Distribution Protocol)
Cisco TDP and LDP MPLS are nearly identical in function,
but use incompatible message formats and some different
procedures.
Tag switched Label switched
TFIB (tag forwarding information
base)
LFIB (label forwarding information base)
TSR (tag switch router) LSR (label switch router)
TSC (tag switched controller) LSC (label switched controller)
ATM-TSR (ATM tag switch router) ATM-LSR (ATM label switch router, such as the Cisco BPX
8650 switch)
TVC (tag VC, tag virtual circuit) LVC (label VC, label virtual circuit)
TSP (tag switch path) LSP (label-switched path)
XTag ATM (extended Tag ATM) port XmplsATM (extended MPLS ATM) port