1. 1 © 2001, Cisco Systems, Inc. MPLS Architecture & Operation Peter Tomsu Senior Consultant EMEA ptomsu@cisco.com Peter Tomsu Senior Consultant EMEA ptomsu@cisco.com

2. 2 © 2001, Cisco Systems, Inc. 2 © 2000, Cisco Systems, Inc. Scalability of IP Based Forwarding MPLS Architecture - A New Paradigm MPLS Building Blocks MPLS Packet Forwarding & Label Switched Paths Frame-mode MPLS - Label Assignment & Distribution Cell-mode MPLS - Label Assignment & Distribution Configuring MPLS Agenda

3. 3 © 2001, Cisco Systems, Inc. Scalability of IP Based Forwarding 3 © 2000, Cisco Systems, Inc.

4. 4 MPLS Arch_Oper_0701© 2001, Cisco Systems, Inc. www.cisco.com London POP router IGP Paris Peering Point Independent hop by hop forwarding decision based on layer-3 header of the incoming packet and routing algorithm output Packet Forwarding - IP Networks Forwarding decision based solely on IP destination address Hop-by-hop connectionless destination-only paradigm No end-to-end paths No QoS or Optimization

5. 5 MPLS Arch_Oper_0701© 2001, Cisco Systems, Inc. www.cisco.com Layer-3 overlay scheme across layer-2 Usually point-to-point links (VCs) connection oriented Full mesh for optimal routing Packet Forwarding – Layer 3 Overlay London Core router Paris Core router Munich Core router ATM Backbone ATM Switch London ATM Switch Paris ATM Switch Munich ATM PVC

6. 6 MPLS Arch_Oper_0701© 2001, Cisco Systems, Inc. www.cisco.com MPLS Architecture A New Paradigm

7. 7 MPLS Arch_Oper_0701© 2001, Cisco Systems, Inc. www.cisco.com MPLS – Multi Protocol Label Switching “ ” draft-ietf-mpls-framework “The primary goal of the MPLS working group is to standardise a base technology that integrates the label swapping forwarding paradigm with network layer routing. Label Swapping is expected to improve price/performance of network layer routing scalability of the network layer provide greater flexibility in the delivery of (new) routing services new routing services can be added without changing the forwarding paradigm

8. 8 MPLS Arch_Oper_0701© 2001, Cisco Systems, Inc. www.cisco.com MPLS Peer Model OSPF, BGP PNNI OSPF, BGP Overlay Model eg Classical IP, MPOA, NHRP Routers and Switches totally isolated Routers have no idea of ATM Topo IP features must be approximately mapped into ATM Peer Model eg MPLS Routers and Switches totally integrated Routers & Switches share topology IP features directly supported by ATM

9. 9 MPLS Arch_Oper_0701© 2001, Cisco Systems, Inc. www.cisco.com London POP router IGP Paris Peering Point Packet forwarding based on labels - no reclassification of packets Label Swapping Multi-protocol Label Switching MPLS Concepts Packets are classified on entry into the MPLS domain Classification can be based on IGP but could be QOS, TE, etc..

10. 10 © 2001, Cisco Systems, Inc. 10 © 2001, Cisco Systems, Inc. MPLS Building Blocks

11. 11 MPLS Arch_Oper_0701© 2001, Cisco Systems, Inc. www.cisco.com MPLS - IP Switching Service 1a. The Routed protocol (OSPF, IGRP,...) computes the shortest path to destination within the core 3. LSR: Label Switch Router switches packet based on label - Label Swapping 4.The last MPLS router removes label 2. ELSR ( Edge LSR ): Inbound router receives packets runs usual L3 services adds labels to packets 1b. The LDP (Label Distribution Protocol) binds a label to every destination address

12. 12 MPLS Arch_Oper_0701© 2001, Cisco Systems, Inc. www.cisco.com Forwarding Component data plane also referred to as the data plane responsible for forwarding packets/cells based on labels uses a label forwarding database maintained by the label switch MPLS Forwarding Component Simple Label Swapping

13. 13 MPLS Arch_Oper_0701© 2001, Cisco Systems, Inc. www.cisco.com MPLS Control Component Control Component control plane also referred to as the control plane label bindings responsible for creating and maintaining label forwarding information (known as label bindings ) forwarding information taken from the FIB label mappings distributed via Label Distribution Protocol The Intelligence

14. 14 MPLS Arch_Oper_0701© 2001, Cisco Systems, Inc. www.cisco.com Cisco Express Forwarding CEFEach LSR must have CEF enabled globally FIB FIB = Forwarding Information Base only IOS layer-3 switching method that uses the FIB table when FIB entry created, label information is taken from the LIB Any interface that will perform label imposition must also have CEF enabled as label imposition references the FIB

15. 15 MPLS Arch_Oper_0701© 2001, Cisco Systems, Inc. www.cisco.com MPLS Specific Tables LIBEach LSR will use a LIB Label Information Base Contains all label/prefix mappings from all TDP/LDP neighbours LFIBEach LSR will also use a LFIB Label Forwarding Information Base Contains only label/prefix mappings that are currently in use for label forwarding

16. 16 MPLS Arch_Oper_0701© 2001, Cisco Systems, Inc. www.cisco.com Control-Plane to Data-Plane Data plane in a node IP Routing Protocol IP Routing Table Control plane in a node Router IGP Routing information exchange with other routers IP FIB Incoming IP packets Outgoing IP packets

17. 17 MPLS Arch_Oper_0701© 2001, Cisco Systems, Inc. www.cisco.com Control-Plane to Data-Plane MPLS / E-LSR Data plane in a node IP Routing Protocol IP Routing Table MPLS LIB Control plane in a node MPLS LFIB E-LSR Edge Label Switch Router IGP Routing information exchange with other routers (Link-state recommended) Label Distribution Protocol Label binding exchange with other routers Incoming labelled packets Outgoing IP packets Outgoing labelled packets Incoming IP packets IP FIB

18. 18 MPLS Arch_Oper_0701© 2001, Cisco Systems, Inc. www.cisco.com Control-Plane to Data-Plane MPLS / LSR Data plane in a node IP Routing Protocol IP Routing Table Control plane in a node LSR Label Switch Router Incoming labelled packets Outgoing labelled packets MPLS LFIB MPLS LIB IGP Routing information exchange with other routers (Link-state recommended) Label Distribution Protocol Label binding exchange with other routers

19. 19 © 2001, Cisco Systems, Inc. 19 © 2001, Cisco Systems, Inc. MPLS Packet Forwarding & Label Switched Paths

20. 20 MPLS Arch_Oper_0701© 2001, Cisco Systems, Inc. www.cisco.com MPLS Example: Routing Information 128.89 171.69 1 0 1 0 You can reach 171.69 through me You can reach 128.89 and 171.69 through me Routing Updates (OSPF, EIGRP, …) You can reach 128.89 through me AddressPrefix 128.89 171.69... OutI’face 0 1... AddressPrefix 128.89 171.69... OutI’face 1 1... AddressPrefix 128.89... OutI’face 0...

21. 21 MPLS Arch_Oper_0701© 2001, Cisco Systems, Inc. www.cisco.com MPLS Example: Assigning Labels 1 0 1 0 Use label 7 for 171.69 Use label 4 for 128.89 and Use label 5 for 171.69 Label Distribution Use label 9 for 128.89 128.89 171.69 InLblAddressPrefix 128.89 171.69... OutI’face 0 1... OutLblInLblAddressPrefix 128.89 171.69... OutI’face 1 1... OutLblInLblAddressPrefix 128.89... OutI’face 0... OutLbl - - 4 5 4 5 9 7 9-

22. 22 MPLS Arch_Oper_0701© 2001, Cisco Systems, Inc. www.cisco.com MPLS Example: Forwarding Packets 128.89 171.69 1 0 1 128.89.25.4Data4128.89.25.4Data 128.89.25.4Data 128.89.25.4Data9 0 Label Switch Forwards Based on Label InLblAddressPrefix 128.89 171.69... OutI’face 0 1... OutLblInLblAddressPrefix 171.69... OutI’face 1 1... OutLblInLblAddressPrefix 128.89... OutI’face 0... - - 4 5 57 - 49 128.89 OutLbl 9

23. 23 MPLS Arch_Oper_0701© 2001, Cisco Systems, Inc. www.cisco.com Label Encapsulation Label header is equal to 4 octets – Label value is 20 bits – Experimental is 3 bits – S (bottom of stack) is 1 bit – TTL (Time to live) is 8 bits 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 Label | CoS|S| TTL

24. 24 MPLS Arch_Oper_0701© 2001, Cisco Systems, Inc. www.cisco.com Label Encapsulation ATM label switching Packet-over-SONET/SDH Ethernet: similar Frame Relay PVCs: similar Label over ATM PVCs PPP Header LabelLabel Layer 3 Header Data Ethernet Hdr LabelLabel Layer 3 Header Data Frame Rly Hdr LabelLabel Layer 3 Header Data ATM Header LabelLabel Layer 3 Header Data ATM Header Data (subsequent cells) GFC VPI VCI LabelLabel PTI CLP HEC Layer 3 Header Data GFC VPI VCI PTI CLP HEC Data (subsequent cells) LabelLabel LabelLabel

25. 25 MPLS Arch_Oper_0701© 2001, Cisco Systems, Inc. www.cisco.com The Label Stack MPLS is recursive 171.68.10/24 Rtr-A Next-Hop InLab 5... AddressPrefix 171.68.10... OutI/F 1... OutLab 7... InI/F 0... IP packet D=171.68.10.12 Label = 5 Label = 21 IP packet D=171.68.10.12 Label = 7 Label = 21 Rtr-A forwards the labeled packet based on the label at the top of the label stack

26. 26 MPLS Arch_Oper_0701© 2001, Cisco Systems, Inc. www.cisco.com Forwarding Equivalent Class FECsIP Packets are classified into FECs Forwarding Equivalent Class group of packets forwarded in the same manner, over the same path, with the same forwarding treatment determined (by default) through the output of the IGP (or static routing) each FEC corresponds to an IP destination prefix destination-based unicast routing (default) could be QOS, all BGP prefixes reachable via a particular exit point etc...

27. 27 MPLS Arch_Oper_0701© 2001, Cisco Systems, Inc. www.cisco.com Label Switch Path (LSP) FEC is determined in LSR-ingress LSR-ingress to LSR-egress path is the same for packets of the same FEC LSPs are derived from IGP routing information LSPs may diverge from IGP shortest path LSP tunnels (explicit routing) with Traffic Engineering LSP follows IGP shortest path IGP domain with a label distribution protocol LSP diverges from IGP shortest path IGP domain with a label distribution protocol

28. 28 MPLS Arch_Oper_0701© 2001, Cisco Systems, Inc. www.cisco.com Frame-mode MPLS Label Assignment & Distribution 28 © 2000, Cisco Systems, Inc.

29. 29 MPLS Arch_Oper_0701© 2001, Cisco Systems, Inc. www.cisco.com Each LSR assigns a local label for each FEC label to IP prefix mapping held within the LIB (Label Information Base) label has local significance Frame-mode Label Assignment London# show tag-switching tdp bindings 197.26.15.0 tib entry: 197.26.15.0/24, rev 7 local binding: tag: 30 remote binding: tsr: 172.16.1.1:0, tag: 33 remote binding: tsr: 172.16.1.2:0, tag: 35 remote binding: tsr: 172.16.1.3:0, tag: 23 remote binding: tsr: 172.16.2.1:0, tag: 59 remote binding: tsr: 172.16.3.1:0, tag: 28

30. 30 MPLS Arch_Oper_0701© 2001, Cisco Systems, Inc. www.cisco.com independent controlFrame-mode LSRs use independent control label assignment as soon as a FEC appears within the IP routing table, a label is assigned and held within the LIB LSR may label forward packets to a next-hop that does not yet have label information for the FEC labels are not assigned to BGP routes Frame-mode Label Assignment

31. 31 MPLS Arch_Oper_0701© 2001, Cisco Systems, Inc. www.cisco.com Frame-mode Label Distribution Labels are exchanged between adjacent LSRs and a binding is agreed binding will be downstream to upstream in respect of traffic flow Applications may require non-adjacent neighbours Traffic Engineering Virtual Private Networks LDP/TDP Directed Peers

32. 32 MPLS Arch_Oper_0701© 2001, Cisco Systems, Inc. www.cisco.com LondonBrusselsParis 197.26.15.0/24 Downstream/Upstream Neighbours 146.15.27.0/24 Paris router is downstream neighbour of Brussels for FEC 197.26.15.0/24 London is downstream neighbour of Brussels for FEC 146.15.27.0/24

33. 33 MPLS Arch_Oper_0701© 2001, Cisco Systems, Inc. www.cisco.com Label mappings are distributed to downstream & upstream neighbours only labels from next-hop neighbour will be used to populate the LFIB (Label Forwarding Information Base) taken from LIB (Label Information Base) Unsolicited downstreamUnsolicited downstream label distribution unsolicited as distribute labels automatically downstream as LSR assigns labels that upstream neighbours can use to forward traffic toward downstream FECs Frame-mode Label Distribution

34. 34 MPLS Arch_Oper_0701© 2001, Cisco Systems, Inc. www.cisco.com Label Distribution Protocols Cisco IOS implements two label binding protocols for the purpose of destination- based unicast routing TDP TDP (Tag Distribution Protocol) proprietary protocol - TCP port 711 LDP LDP (Label Distribution Protocol) IETF standards based protocol - TCP port 646 Both protocols are functionally equivalent and can be used concurrently

35. 35 MPLS Arch_Oper_0701© 2001, Cisco Systems, Inc. www.cisco.com LondonBrusselsParis 197.26.15.0/24 In Label FEC Out Label - 197.26.15.0/24 28 In Label FEC Out Label 28 197.26.15.0/24 41 In Label FEC Out Label 41 197.26.15.0/24 - Use label 28 for destination 197.26.15.0/24 Use label 41 for destination 197.26.15.0/24 Frame-mode Label Distribution

36. 36 MPLS Arch_Oper_0701© 2001, Cisco Systems, Inc. www.cisco.com Label Retention liberalFrame-mode LSR uses liberal retention mode LSR keeps labels from neighbours that are not the best next-hop for the FEC requires more memory and label space problem for ATM-LSR as label is a VC improves convergence if layer-3 routing information changes, next-hop label forwarding information is already available

37. 37 MPLS Arch_Oper_0701© 2001, Cisco Systems, Inc. www.cisco.com P-1 P-2 Liberal Label Retention LIB contains mappings from ALL neighbours P-3 Use label 41 for destination 197.26.15.1/32 Use label 21 for destination 197.26.15.1/32 Use label 23 for destination 197.26.15.1/32 Use label 25 for destination 197.26.15.1/32 P-4 P-5 Use label 21 for destination 197.26.15.1/32 In Label FEC Out Label 24 197.26.15.1/32 23 local binding: tag: 24 remote binding: tsr: 172.16.1.1:0, tag: 23 remote binding: tsr: 172.16.1.2:0, tag: 41

38. 38 MPLS Arch_Oper_0701© 2001, Cisco Systems, Inc. www.cisco.com Penultimate Hop Popping Frame-mode LSR may use Penultimate Hop Popping procedures during label forwarding label at top of stack is removed (popped) by the upstream neighbour of the egress-LSR requested by egress-LSR using TDP/LDP uses implicit-null label one lookup saved at egress-LSR

39. 39 MPLS Arch_Oper_0701© 2001, Cisco Systems, Inc. www.cisco.com Penultimate Hop Popping LondonBrusselsParis 197.26.15.1/32 In Label FEC Out Label - 197.26.15.1/32 28 In Label FEC Out Label 28 197.26.15.1/32 POP In Label FEC Out Label - 197.26.15.1/32 - Use label 28 for destination 197.26.15.1/32 Use label implicit-null for destination 197.26.15.1/32 Paris# show tag-switching tdp binding 197.26.15.1 tib entry: 197.26.15.1/32, rev 10 local binding: tag: imp-null(1) remote binding: tsr: 172.16.3.1:0, tag: 28 Brussels# show tag-switching tdp binding 197.26.15.1 tib entry: 197.26.15.1/32, rev 10 local binding: tag: 28 remote binding: tsr: 172.16.3.2:0, tag: imp-null(1) Brussels# show tag-switching forwarding Local Outgoing Prefix Bytes tag Outgoing Next Hop tag tag or VC or Tunnel Id switched interface 28 Pop tag 197.26.15.1/32 0 Se0/0/2 point2point

40. 40 MPLS Arch_Oper_0701© 2001, Cisco Systems, Inc. www.cisco.com Cell-mode MPLS Label Assignment & Distribution 40 © 2000, Cisco Systems, Inc.

41. 41 MPLS Arch_Oper_0701© 2001, Cisco Systems, Inc. www.cisco.com Cell-Mode MPLS ATM switches cannot perform MPLS label or IP lookup Packets exchanged as cells at layer-2 VPI/VCI pair used as label ATM switches cannot directly exchange IP traffic VC required for MPLS data plane Control VC used for MPLS control plane

42. 42 MPLS Arch_Oper_0701© 2001, Cisco Systems, Inc. www.cisco.com Label Switch Router IP Routing Protocols IP Routing Table MPLS Signalling Protocol Label Forwarding Table Control Plane Data Plane Label Switch Router IP Routing Protocols IP Routing Table MPLS Signalling Protocol Label Forwarding Table Control Plane Data Plane Routing Information Exchange Label Binding Exchange Labelled Packets IP & MPLS Adjacencies Control VC

43. 43 MPLS Arch_Oper_0701© 2001, Cisco Systems, Inc. www.cisco.com MPLS Control VC ATM Edge LSR MPLS Control Plane ATM LSR MPLS Control Plane ATM Data Plane Switching Matrix ATM Control VC (0/32) - aal5snap

44. 44 MPLS Arch_Oper_0701© 2001, Cisco Systems, Inc. www.cisco.com 5 5 8 8 InTag 240/5 240/8... AddressPrefix 128.89 128.89... OutI/F 0 0... OutTag 240/3 240/3... InI/F 1 2... 2 5 8 333333 Packet Cells 128.89 ? 1 0 Packet 5 8 5 5 5 3 8 3 8 8 8 3333 Cell-mode Label Distribution Unsolicited Downstream label distribution breaks ATM ! (because use of same label for same FEC)

45. 45 MPLS Arch_Oper_0701© 2001, Cisco Systems, Inc. www.cisco.com 5 5 8 8 InTag 240/5 240/8... AddressPrefix 128.89 128.89... OutI/F 0 0... OutTag 240/3 240/7... InI/F 1 2... 2 5 8 737373 Packet Cells 128.89 Now I am happy :) 1 0 Packet 5 8 5 5 5 7 8 7 8 8 8 3373 Cell Flow with Multiple Labels Cell-mode uses Downstream on Demand label distribution with Ordered label allocation unique label mapping for each upstream neighbour multiple labels for the same FEC from the same next-hop neighbour

46. 46 MPLS Arch_Oper_0701© 2001, Cisco Systems, Inc. www.cisco.com Cell-mode Label Distribution London POP router Paris Peering Point Step #1: Label request for 146.27.15.0/24 sent to next-hop neighbour 146.27.15.0/24 Step #2: Paris allocates label and responds with label mapping Step #3: Label mapping is propagated back to the source and labels are assigned by intermediate ATM LSRs RQ for 146.27.15.0/24 146.27.15.0/24 = 1/241 146.27.15.0/24 = 1/239 146.27.15.0/24 = 1/244

47. 47 MPLS Arch_Oper_0701© 2001, Cisco Systems, Inc. www.cisco.com Cell-mode Label Retention Cell-mode uses Conservative label retention mode keep only labels that are relevant to forwarding achieved by requesting label mapping ONLY from next- hop downstream neighbour 146.27.52.0/24 Label request to next-hop neighbour only Two paths available to 146.27.52.0/24

48. 48 MPLS Arch_Oper_0701© 2001, Cisco Systems, Inc. www.cisco.com VC Merge Further technique to reduce label space is vc-merge 5 5 8 8 InTag 240/5 240/8... AddressPrefix 128.89 128.89... OutI/F 0 0... OutTag 240/3 240/3... InI/F 1 2... 5 8 Packet Cells 128.89 ATM LSR transmits cells in sequence so that the downstream LSR is able to correctly reassemble the cells into packets 1 Packet 5 8 5 5 5 8 8 8 8 333 3333 3 3

49. 49 © 2001, Cisco Systems, Inc. 49 © 2000, Cisco Systems, Inc. Configuring MPLS

50. 50 MPLS Arch_Oper_0701© 2001, Cisco Systems, Inc. www.cisco.com Configure MPLS tag-switchingipGlobal: tag-switching ip is by default On all interfaces in the backbone : tag-switching ip mpls ip (or) mpls ip Label distribution : – TDP – LDP 12.0(10)ST 12.1(1)T

51. 51 MPLS Arch_Oper_0701© 2001, Cisco Systems, Inc. www.cisco.com Debug sh tag tdp discov-> Broadcast Discovery neighbors protocol sh tag tdp nei-> TDP (TCP session 711) sh tag tdp bind-> Full label exchange with all neighbors sh ip cef-> Select next-hop sh tag forwarding -> View selected Tag for destination sh ip cef IP@ det-> View all forwarding infos (& multi-labels) traceroute IP@-> View LSP (path & tags & multi-tags) debug tag pac-> View LSR (P router) switching

52. 52 MPLS Arch_Oper_0701© 2001, Cisco Systems, Inc. www.cisco.com LDP - Discovery sh tag tdp discovery Local TDP Identifier: 10.21.2.2:0 TDP Discovery Sources: Interfaces: Serial0/0: xmit/recv TDP Id: 10.1.2.2:0 Serial0/1: xmit/recv TDP Id: 10.21.4.4:0 Serial1/0: xmit/recv TDP Id: 10.21.3.3:0 sh tag tdp discovery Local TDP Identifier: 10.21.2.2:0 TDP Discovery Sources: Interfaces: Serial0/0: xmit/recv TDP Id: 10.1.2.2:0 Serial0/1: xmit/recv TDP Id: 10.21.4.4:0 Serial1/0: xmit/recv TDP Id: 10.21.3.3:0

53. 53 MPLS Arch_Oper_0701© 2001, Cisco Systems, Inc. www.cisco.com Adjacency TDP / LDP sh tag tdp neighbor Peer TDP Ident: 10.21.4.4:0; Local TDP Ident 10.21.2.2:0 TCP connection: 10.21.4.4.11001 - 10.21.2.2.711 State: Oper; PIEs sent/rcvd: 54/50; ; Downstream Up time: 00:37:57 TDP discovery sources: Serial0/1 Addresses bound to peer TDP Ident: 10.21.140.4 10.21.4.4 10.21.46.4 10.21.24.4 Peer TDP Ident: 10.21.3.3:0; Local TDP Ident 10.21.2.2:0 TCP connection: 10.21.3.3.11266 - 10.21.2.2.711 State: Oper; PIEs sent/rcvd: 24/25; ; Downstream Up time: 00:17:45 TDP discovery sources: Serial1/0 Addresses bound to peer TDP Ident: 10.21.130.3 10.21.3.3 10.21.13.3 10.21.35.3 10.21.23.3 sh tag tdp neighbor Peer TDP Ident: 10.21.4.4:0; Local TDP Ident 10.21.2.2:0 TCP connection: 10.21.4.4.11001 - 10.21.2.2.711 State: Oper; PIEs sent/rcvd: 54/50; ; Downstream Up time: 00:37:57 TDP discovery sources: Serial0/1 Addresses bound to peer TDP Ident: 10.21.140.4 10.21.4.4 10.21.46.4 10.21.24.4 Peer TDP Ident: 10.21.3.3:0; Local TDP Ident 10.21.2.2:0 TCP connection: 10.21.3.3.11266 - 10.21.2.2.711 State: Oper; PIEs sent/rcvd: 24/25; ; Downstream Up time: 00:17:45 TDP discovery sources: Serial1/0 Addresses bound to peer TDP Ident: 10.21.130.3 10.21.3.3 10.21.13.3 10.21.35.3 10.21.23.3

54. 54 MPLS Arch_Oper_0701© 2001, Cisco Systems, Inc. www.cisco.com View the LIB sh tag tdp binding tib entry: 10.21.5.5/32, rev 34 local binding: tag: 34 remote binding: tsr: 10.21.4.4:0, tag: 35 remote binding: tsr: 10.21.3.3:0, tag: 28 remote binding: tsr: 10.1.2.2:0, tag: 38 sh tag tdp binding tib entry: 10.21.5.5/32, rev 34 local binding: tag: 34 remote binding: tsr: 10.21.4.4:0, tag: 35 remote binding: tsr: 10.21.3.3:0, tag: 28 remote binding: tsr: 10.1.2.2:0, tag: 38 tib entry: 10.21.13.0/24, rev 16 local binding: tag: 28 remote binding: tsr: 10.21.4.4:0, tag: 31 remote binding: tsr: 10.21.3.3:0, tag: imp-null remote binding: tsr: 10.1.2.2:0, tag: imp-null tib entry: 10.21.13.0/24, rev 16 local binding: tag: 28 remote binding: tsr: 10.21.4.4:0, tag: 31 remote binding: tsr: 10.21.3.3:0, tag: imp-null remote binding: tsr: 10.1.2.2:0, tag: imp-null

55. 55 MPLS Arch_Oper_0701© 2001, Cisco Systems, Inc. www.cisco.com View the LFIB 3640-L21-R2# sh tag forwarding-table Local Outgoing Prefix Bytes tag Outgoing Next Hop tag tag or VC or Tunnel Id switched interface 17 Aggregate 100.10.57.0/24[V] 0 21 20 10.10.4.4/32 0 Se0/1 point2point 22 17 10.10.12.0/24 0 Se0/1 point2point 26 Untagged 10.21.24.4/32 0 Se0/1 point2point 27 Untagged 10.21.23.3/32 0 Se1/0 point2point 28 Pop tag 10.21.13.0/24 0 Se0/0 point2point Pop tag 10.21.13.0/24 0 Se1/0 point2point 29 Pop tag 10.21.35.0/24 0 Se1/0 point2point 30 Pop tag 10.21.3.3/32 0 Se1/0 point2point 32 Pop tag 10.21.4.4/32 0 Se0/1 point2point 33 27 10.21.57.0/24 0 Se1/0 point2point 34 28 10.21.5.5/32 0 Se1/0 point2point 35 Untagged 10.21.12.1/32 0 Se0/0 point2point 36 Pop tag 10.1.2.2/32 0 Se0/0 point2point 3640-L21-R2# sh tag forwarding-table Local Outgoing Prefix Bytes tag Outgoing Next Hop tag tag or VC or Tunnel Id switched interface 17 Aggregate 100.10.57.0/24[V] 0 21 20 10.10.4.4/32 0 Se0/1 point2point 22 17 10.10.12.0/24 0 Se0/1 point2point 26 Untagged 10.21.24.4/32 0 Se0/1 point2point 27 Untagged 10.21.23.3/32 0 Se1/0 point2point 28 Pop tag 10.21.13.0/24 0 Se0/0 point2point Pop tag 10.21.13.0/24 0 Se1/0 point2point 29 Pop tag 10.21.35.0/24 0 Se1/0 point2point 30 Pop tag 10.21.3.3/32 0 Se1/0 point2point 32 Pop tag 10.21.4.4/32 0 Se0/1 point2point 33 27 10.21.57.0/24 0 Se1/0 point2point 34 28 10.21.5.5/32 0 Se1/0 point2point 35 Untagged 10.21.12.1/32 0 Se0/0 point2point 36 Pop tag 10.1.2.2/32 0 Se0/0 point2point

56. 56 MPLS Arch_Oper_0701© 2001, Cisco Systems, Inc. www.cisco.com View the LFIB L10-R5# sh tag forwarding tag 34 detail Local Outgoing Prefix Bytes tag Outgoing Next Hop tag tag or VC or Tunnel Id switched interface 34 16 100.20.57.0/24[V] 0 Se0/1 point2point MAC/Encaps=4/12, MTU=1496, Tag Stack{16 60} 0F008847 000100000003C000 VPN route: RED No output feature configured Per-packet load-sharing L10-R5# sh tag forwarding tag 34 detail Local Outgoing Prefix Bytes tag Outgoing Next Hop tag tag or VC or Tunnel Id switched interface 34 16 100.20.57.0/24[V] 0 Se0/1 point2point MAC/Encaps=4/12, MTU=1496, Tag Stack{16 60} 0F008847 000100000003C000 VPN route: RED No output feature configured Per-packet load-sharing

57. 57 MPLS Arch_Oper_0701© 2001, Cisco Systems, Inc. www.cisco.com