HP FlexNetwork HSR6600 User manual

HPE FlexNetwork HSR6600 Routers
Comware 7 MPLS Configuration Guide
Part number: 5200-3476
Software version: HSR6602-CMW710-R7607
Document version: 6W100-20170412

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Contents
Configuring basic MPLS ····································································1
Overview··································································································································1
Basic concepts ···················································································································1
MPLS network architecture····································································································2
LSP establishment···············································································································3
MPLS forwarding·················································································································4
PHP ·································································································································5
Protocols and standards ·······································································································5
MPLS configuration task list ·········································································································5
Enabling MPLS ·························································································································6
Setting MPLS MTU·····················································································································6
Specifying the label type advertised by egress ·················································································7
Configuring TTL propagation········································································································8
Enabling sending MPLS TTL-expired messages···············································································9
Enabling MPLS forwarding statistics ······························································································9
Enabling FTN forwarding statistics ··························································································9
Enabling MPLS label forwarding statistics···············································································10
Enabling split horizon for MPLS forwarding····················································································10
Enabling SNMP notifications for MPLS ·························································································10
Displaying and maintaining MPLS ·······························································································11
Configuring a static LSP ··································································12
Overview································································································································12
Configuration guidelines············································································································12
Configuration prerequisites ········································································································12
Configuration procedure············································································································13
Displaying static LSPs···············································································································13
Static LSP configuration example································································································13
Network requirements ········································································································13
Configuration restrictions and guidelines ················································································14
Configuration procedure ·····································································································14
Verifying the configuration···································································································15
Configuring LDP ············································································17
Overview································································································································17
Terminology·····················································································································17
LDP messages ·················································································································17
LDP operation ··················································································································18
Label distribution and control ·······························································································19
LDP GR ··························································································································21
LDP NSR·························································································································22
LDP-IGP synchronization····································································································23
LDP FRR·························································································································23
LDP over MPLS TE ···········································································································24
Protocols·························································································································25
LDP configuration task list··········································································································25
Enabling LDP··························································································································26
Enabling LDP globally ········································································································26
Enabling LDP on an interface·······························································································26
Configuring Hello parameters ·····································································································26
Configuring LDP session parameters ···························································································27
Configuring LDP backoff············································································································29
Configuring LDP MD5 authentication····························································································29
Configuring LDP to redistribute BGP unicast routes·········································································30
Configuring an LSP generation policy···························································································30
Configuring the LDP label distribution control mode·········································································31
Configuring a label advertisement policy·······················································································31

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Configuring a label acceptance policy···························································································32
Configuring LDP loop detection···································································································33
Configuration restrictions and guidelines ················································································34
Configuration procedure ·····································································································34
Configuring LDP session protection ·····························································································34
Configuring LDP GR·················································································································35
Configuring LDP NSR···············································································································35
Configuring LDP-IGP synchronization ··························································································35
Configuring LDP-OSPF synchronization·················································································35
Configuring LDP IS-IS synchronization···················································································37
Configuring LDP FRR ···············································································································37
Setting a DSCP value for outgoing LDP packets·············································································37
Resetting LDP sessions ············································································································38
Enabling SNMP notifications for LDP ···························································································38
Displaying and maintaining LDP··································································································38
IPv4 LDP configuration examples································································································39
LDP LSP configuration example ···························································································39
Label acceptance control configuration example ······································································43
Label advertisement control configuration example···································································47
LDP FRR configuration example···························································································52
IPv6 LDP configuration examples································································································55
IPv6 LDP LSP configuration example ····················································································55
IPv6 label acceptance control configuration example ································································60
IPv6 label advertisement control configuration example·····························································64
Configuring MPLS TE ·····································································71
Overview································································································································71
TE and MPLS TE ··············································································································71
MPLS TE basic concepts····································································································71
Static CRLSP establishment································································································71
Dynamic CRLSP establishment····························································································71
CRLSP establishment using PCE path calculation····································································73
Traffic forwarding ··············································································································74
Make-before-break ············································································································75
Route pinning···················································································································76
Tunnel reoptimization·········································································································76
Automatic bandwidth adjustment ··························································································76
CRLSP backup·················································································································77
FRR ·······························································································································77
DiffServ-aware TE·············································································································78
Bidirectional MPLS TE tunnel·······························································································80
CBTS······························································································································80
Protocols and standards ·····································································································81
MPLS TE configuration task list···································································································82
Enabling MPLS TE···················································································································83
Configuring a tunnel interface·····································································································84
Configuring DS-TE···················································································································84
Configuring an MPLS TE tunnel to use a static CRLSP····································································85
Configuring an MPLS TE tunnel to use a dynamic CRLSP································································86
Configuration task list·········································································································86
Configuring MPLS TE attributes for a link ···············································································86
Advertising link TE attributes by using IGP TE extension ···························································87
Configuring MPLS TE tunnel constraints ················································································88
Establishing an MPLS TE tunnel by using RSVP-TE·································································90
Controlling CRLSP path selection ·························································································90
Controlling MPLS TE tunnel setup ························································································92
Configuring an MPLS TE tunnel to use a CRLSP calculated by PCEs·················································95
Configuring a PCE·············································································································95
Discovering PCEs ·············································································································95
Establishing a CRLSP by using the path calculated by PCEs······················································95
Establishing a backup CRLSP by using the path calculated by PCEs ···········································96
Configuring stateful PCE on a PCC·······················································································96

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Configuring PCEP session parameters ··················································································97
Configuring traffic forwarding······································································································97
Configuring static routing to direct traffic to an MPLS TE tunnel···················································97
Configuring PBR to direct traffic to an MPLS TE tunnel······························································98
Configuring automatic route advertisement to direct traffic to an MPLS TE tunnel····························98
Configuring a bidirectional MPLS TE tunnel···················································································99
Restrictions and guidelines··································································································99
Prerequisites····················································································································99
Configuring the active end of a co-routed bidirectional MPLS TE tunnel ······································ 100
Configuring the passive end of a co-routed bidirectional MPLS TE tunnel···································· 100
Configuring an associated bidirectional MPLS TE tunnel·························································· 100
Configuring CRLSP backup······································································································ 100
Configuring MPLS TE FRR ······································································································ 101
Enabling FRR················································································································· 101
Configuring a bypass tunnel on the PLR··············································································· 101
Configuring node fault detection ························································································· 105
Setting the optimal bypass tunnel selection interval ································································ 106
Configuring CBTS·················································································································· 106
Enabling SNMP notifications for MPLS TE ·················································································· 106
Displaying and maintaining MPLS TE························································································· 107
MPLS TE configuration examples······························································································ 108
Establishing an MPLS TE tunnel over a static CRLSP····························································· 108
Establishing an MPLS TE tunnel with RSVP-TE····································································· 112
Establishing an inter-AS MPLS TE tunnel with RSVP-TE························································· 118
Establishing an inter-area MPLS TE tunnel over a CRLSP calculated by PCEs ···························· 125
Bidirectional MPLS TE tunnel configuration example······························································· 130
CRLSP backup configuration example················································································· 136
Manual bypass tunnel for FRR configuration example····························································· 140
Auto FRR configuration example ························································································ 145
IETF DS-TE configuration example ····················································································· 151
CBTS configuration example ····························································································· 158
Troubleshooting MPLS TE······································································································· 162
No TE LSA generated ······································································································ 162
Configuring a static CRLSP···························································· 164
Overview······························································································································ 164
Configuration procedure·········································································································· 164
Displaying static CRLSPs ········································································································ 165
Static CRLSP configuration example·························································································· 165
Network requirements ······································································································ 165
Configuration procedure ··································································································· 166
Verifying the configuration································································································· 168
Configuring RSVP········································································ 171
Overview······························································································································ 171
RSVP messages············································································································· 171
CRLSP setup procedure··································································································· 172
RSVP refresh mechanism ································································································· 172
RSVP authentication········································································································ 173
RSVP GR······················································································································ 173
Protocols and standards ··································································································· 174
RSVP configuration task list ····································································································· 174
Enabling RSVP ····················································································································· 174
Configuring RSVP refresh········································································································ 174
Configuring RSVP Srefresh and reliable RSVP message delivery ···················································· 175
Configuring RSVP hello extension····························································································· 175
Configuring RSVP authentication ······························································································ 176
Setting a DSCP value for outgoing RSVP packets ········································································ 177
Configuring RSVP GR············································································································· 178
Enabling BFD for RSVP ·········································································································· 178
Displaying and maintaining RSVP ····························································································· 178
RSVP configuration examples ·································································································· 179

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Establishing an MPLS TE tunnel with RSVP-TE····································································· 179
RSVP GR configuration example························································································ 185
Configuring tunnel policies ····························································· 188
Overview······························································································································ 188
Configuring a tunnel policy······································································································· 188
Configuration guidelines ··································································································· 188
Configuration procedure ··································································································· 189
Displaying tunnel information···································································································· 189
Tunnel policy configuration examples························································································· 190
Preferred tunnel configuration example················································································ 190
Exclusive tunnel configuration example················································································ 190
Tunnel selection order configuration example········································································ 191
Preferred tunnel and tunnel selection order configuration example············································· 191
Configuring MPLS L3VPN······························································ 194
Overview······························································································································ 194
Basic MPLS L3VPN architecture ························································································ 194
MPLS L3VPN concepts ···································································································· 194
MPLS L3VPN route advertisement······················································································ 196
MPLS L3VPN packet forwarding························································································· 197
MPLS L3VPN networking schemes····················································································· 198
Inter-AS VPN·················································································································· 200
Carrier's carrier··············································································································· 204
Nested VPN··················································································································· 206
Multirole host·················································································································· 207
HoVPN·························································································································· 208
OSPF VPN extension······································································································· 210
BGP AS number substitution and SoO attribute ····································································· 212
MPLS L3VPN FRR ·········································································································· 213
Protocols and standards ··································································································· 215
MPLS L3VPN configuration task list··························································································· 215
Configuring basic MPLS L3VPN································································································ 216
Configuration prerequisites································································································ 216
Configuring VPN instances································································································ 216
Configuring routing between a PE and a CE·········································································· 218
Configuring routing between PEs························································································ 223
Configuring BGP VPNv4 route control·················································································· 223
Configuring inter-AS VPN ········································································································ 225
Configuring inter-AS option A····························································································· 225
Configuring inter-AS option B····························································································· 225
Configuring inter-AS option C····························································································· 226
Configuring nested VPN·········································································································· 229
Configuring multirole host ········································································································ 230
Configuring and applying PBR ··························································································· 230
Configuring a static route ·································································································· 231
Configuring HoVPN················································································································ 231
Configuring an OSPF sham link ································································································ 232
Configuring a loopback interface························································································· 233
Redistributing the loopback interface address········································································ 233
Creating a sham link ········································································································ 233
Specifying the VPN label processing mode on the egress PE·························································· 234
Configuring BGP AS number substitution and SoO attribute···························································· 234
Configuring MPLS L3VPN FRR································································································· 235
Configuring the LPU load sharing mode······················································································ 237
Configuring route replication····································································································· 237
About route replication······································································································ 237
Procedure······················································································································ 237
Enabling SNMP notifications for MPLS L3VPN············································································· 238
Displaying and maintaining MPLS L3VPN··················································································· 238
MPLS L3VPN configuration examples························································································ 239
Configuring basic MPLS L3VPN························································································· 239

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Configuring MPLS L3VPN over a GRE tunnel········································································ 245
Configuring a hub-spoke network························································································ 249
Configuring MPLS L3VPN inter-AS option A·········································································· 255
Configuring MPLS L3VPN inter-AS option B·········································································· 260
Configuring MPLS L3VPN inter-AS option C ········································································· 265
Configuring MPLS L3VPN carrier's carrier in the same AS ······················································· 272
Configuring MPLS L3VPN carrier's carrier in different ASs ······················································· 279
Configuring nested VPN ··································································································· 287
Configuring multirole host·································································································· 296
Configuring HoVPN ········································································································· 297
Configuring an OSPF sham link·························································································· 305
Configuring BGP AS number substitution ············································································· 309
Configuring BGP AS number substitution and SoO attribute····················································· 313
Configuring MPLS L3VPN FRR through VPNv4 route backup for a VPNv4 route ·························· 315
Configuring MPLS L3VPN FRR through VPNv4 route backup for an IPv4 route···························· 317
Configuring MPLS L3VPN FRR through IPv4 route backup for a VPNv4 route······························ 319
Configuring IPv6 MPLS L3VPN······················································· 322
Overview······························································································································ 322
IPv6 MPLS L3VPN packet forwarding·················································································· 322
IPv6 MPLS L3VPN routing information advertisement····························································· 323
IPv6 MPLS L3VPN network schemes and features································································· 323
Protocols and standards ··································································································· 324
IPv6 MPLS L3VPN configuration task list···················································································· 324
Configuring basic IPv6 MPLS L3VPN························································································· 324
Configuration prerequisites································································································ 324
Configuring VPN instances································································································ 324
Configuring routing between a PE and a CE·········································································· 327
Configuring routing between PEs························································································ 332
Configuring BGP VPNv6 route control·················································································· 332
Configuring inter-AS IPv6 VPN ································································································· 334
Configuring inter-AS IPv6 VPN option A··············································································· 334
Configuring inter-AS IPv6 VPN option B··············································································· 335
Configuring inter-AS IPv6 VPN option C··············································································· 336
Configuring multirole host ········································································································ 337
Configuring and applying IPv6 PBR····················································································· 337
Configuring an IPv6 static route·························································································· 338
Configuring an OSPFv3 sham link····························································································· 338
Configuring a loopback interface························································································· 338
Redistributing the loopback interface address········································································ 339
Creating a sham link ········································································································ 339
Configuring BGP AS number substitution and SoO attribute···························································· 339
Displaying and maintaining IPv6 MPLS L3VPN ············································································ 340
IPv6 MPLS L3VPN configuration examples ················································································· 341
Configuring IPv6 MPLS L3VPNs························································································· 341
Configuring an IPv6 MPLS L3VPN over a GRE tunnel····························································· 348
Configuring IPv6 MPLS L3VPN inter-AS option A··································································· 351
Configuring IPv6 MPLS L3VPN inter-AS option B··································································· 356
Configuring IPv6 MPLS L3VPN inter-AS option C··································································· 361
Configuring IPv6 MPLS L3VPN carrier's carrier in the same AS ················································ 367
Configuring multirole host·································································································· 375
Configuring an OSPFv3 sham link ······················································································ 377
Configuring BGP AS number substitution ············································································· 381
Configuring BGP AS number substitution and SoO attribute····················································· 385
Configuring MPLS L2VPN······························································ 389
Overview······························································································································ 389
Basic concepts of MPLS L2VPN························································································· 389
MPLS L2VPN network models ··························································································· 390
Remote connection establishment ······················································································ 391
Local connection establishment·························································································· 392
PW data encapsulation types····························································································· 392

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Control word··················································································································· 394
MPLS L2VPN interworking································································································ 394
PW redundancy ·············································································································· 395
Multi-segment PW··········································································································· 395
VCCV ··························································································································· 397
Hardware and feature compatibility···························································································· 397
MPLS L2VPN configuration task list··························································································· 397
Enabling L2VPN ···················································································································· 398
Configuring an AC·················································································································· 398
Configuring a Layer 3 interface··························································································· 398
Configuring a cross-connect····································································································· 399
Configuring a PW··················································································································· 400
Configuring a PW class ···································································································· 400
Configuring a static PW ···································································································· 400
Configuring an LDP PW···································································································· 401
Configuring a BGP PW····································································································· 401
Configuring a remote CCC connection················································································· 403
Binding an AC to a cross-connect······························································································ 404
Binding a Layer 3 interface to a cross-connect······································································· 404
Configuring PW redundancy····································································································· 405
Configuring static PW redundancy ······················································································ 405
Configuring LDP PW redundancy ······················································································· 406
Configuring interworking for a cross-connect················································································ 406
Enabling SNMP notifications for L2VPN PW ················································································ 407
Displaying and maintaining MPLS L2VPN··················································································· 407
MPLS L2VPN configuration examples························································································ 408
Configuring local MPLS L2VPN connections ········································································· 408
Configuring IP interworking over local MPLS L2VPN connections·············································· 409
Configuring a static PW ···································································································· 411
Configuring an LDP PW···································································································· 414
Configuring IP interworking over an LDP PW········································································· 418
Configuring a BGP PW····································································································· 422
Configuring a remote CCC connection················································································· 426
Configuring an intra-domain multi-segment PW ····································································· 429
Configuring an inter-domain multi-segment PW ····································································· 432
Configuring VPLS········································································· 439
Overview······························································································································ 439
Basic VPLS architecture ··································································································· 439
VPLS implementation······································································································· 440
H-VPLS························································································································· 442
Hub-spoke networking······································································································ 444
VPLS configuration task list······································································································ 444
Enabling L2VPN ···················································································································· 445
Configuring an AC·················································································································· 445
Configuring a Layer 3 interface··························································································· 446
Configuring a VSI··················································································································· 446
Configuring a PW··················································································································· 446
Configuring a PW class ···································································································· 446
Configuring a static PW ···································································································· 447
Configuring an LDP PW···································································································· 447
Configuring a BGP PW····································································································· 448
Configuring a BGP auto-discovery LDP PW·········································································· 450
Binding an AC to a VSI············································································································ 452
Binding a Layer 3 interface to a VSI····················································································· 452
Configuring UPE dual homing··································································································· 452
Configuring static PW redundancy ······················································································ 453
Configuring LDP PW redundancy ······················································································· 453
Configuring MAC address learning ···························································································· 454
Enabling SNMP notifications for L2VPN PW ················································································ 454
Displaying and maintaining VPLS······························································································ 455
VPLS configuration examples··································································································· 456

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Static PW configuration example ························································································ 456
LDP PW configuration example·························································································· 460
BGP PW configuration example ························································································· 462
BGP auto-discovery LDP PW configuration example······························································· 466
H-VPLS using MPLS access configuration example································································ 471
H-VPLS UPE dual homing configuration example··································································· 475
Configuring L2VPN access to L3VPN or IP backbone·························· 481
Overview······························································································································ 481
Conventional L2VPN access to L3VPN or IP backbone ··························································· 481
Improved L2VPN access to L3VPN or IP backbone································································ 482
Configuring conventional L2VPN access to L3VPN or IP backbone ·················································· 483
Configuring improved L2VPN access to L3VPN or IP backbone······················································· 483
Configuring an L2VE interface···························································································· 484
Configuring an L3VE interface···························································································· 484
Displaying and maintaining L2VPN access to L3VPN or IP backbone ··············································· 485
Improved L2VPN access to L3VPN or IP backbone configuration examples······································· 485
Access to MPLS L3VPN through an LDP MPLS L2VPN ·························································· 485
Access to IP backbone through an LDP VPLS······································································· 491
Configuring MPLS OAM ································································ 496
Overview······························································································································ 496
MPLS ping····················································································································· 496
MPLS tracert·················································································································· 496
BFD for MPLS ················································································································ 496
Periodic MPLS tracert ······································································································ 497
Protocols and standards·········································································································· 497
Configuring MPLS OAM for LSP tunnels····················································································· 497
Configuring MPLS ping for LSPs ························································································ 497
Configuring MPLS tracert for LSPs······················································································ 498
Configuring BFD for LSPs································································································· 498
Configuring periodic MPLS tracert for LSPs ·········································································· 499
Configuring MPLS OAM for MPLS TE tunnels·············································································· 499
Configuring MPLS ping for MPLS TE tunnels ········································································ 499
Configuring MPLS tracert for MPLS TE tunnels······································································ 500
Configuring BFD for MPLS TE tunnels················································································· 500
Configuring MPLS OAM for a PW······························································································ 501
Configuring MPLS ping for a PW ························································································ 501
Configuring BFD for a PW································································································· 501
Displaying MPLS OAM············································································································ 505
BFD for LSP configuration example ··························································································· 505
Network requirements ······································································································ 505
Configuration procedure ··································································································· 505
Verifying the configuration································································································· 507
Configuring MCE·········································································· 508
MPLS L3VPN overview··········································································································· 508
Basic MPLS L3VPN architecture ························································································ 508
MPLS L3VPN concepts ···································································································· 508
MCE overview······················································································································· 510
MCE configuration task list······································································································· 511
Configuring VPN instances ······································································································ 511
Creating a VPN instance··································································································· 512
Associating a VPN instance with an interface ········································································ 512
Configuring route related attributes for a VPN instance···························································· 512
Configuring routing on an MCE································································································· 513
Configuring routing between an MCE and a VPN site······························································ 514
Configuring routing between an MCE and a PE ····································································· 518
Displaying and maintaining MCE······························································································· 521
MCE configuration example ····································································································· 521
Network requirements ······································································································ 521
Configuration procedure ··································································································· 522

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Verifying the configuration································································································· 526
Configuring IPv6 MCE··································································· 527
IPv6 MPLS L3VPN overview ···································································································· 527
IPv6 MCE overview················································································································ 527
IPv6 MCE configuration task list································································································ 527
Configuring VPN instances ······································································································ 528
Creating a VPN instance··································································································· 528
Associating a VPN instance with an interface ········································································ 528
Configuring route related attributes for a VPN instance···························································· 529
Configuring routing on an MCE································································································· 530
Configuring routing between an MCE and a VPN site······························································ 530
Configuring routing between an MCE and a PE ····································································· 535
Displaying and maintaining IPv6 MCE························································································ 537
IPv6 MCE configuration example······························································································· 538
Network requirements ······································································································ 538
Configuration procedure ··································································································· 538
Verifying the configuration································································································· 542
Configuring static SR over MPLS····················································· 544
Overview······························································································································ 544
About SR and SRLSP ······································································································ 544
How static SR over MPLS works························································································· 544
Protocols and standards ··································································································· 545
Static SR over MPLS configuration task list ················································································· 545
Prerequisites························································································································· 545
Configuring an adjacency path·································································································· 546
Configuring a static SRLSP······································································································ 546
Binding a static SRLSP to an MPLS TE tunnel interface································································· 546
Displaying and maintaining static SRLSP···················································································· 547
Static SRLSP configuration examples ························································································ 547
Network requirements ······································································································ 547
Configuration procedure ··································································································· 548
Verifying the configuration································································································· 551
Document conventions and icons ···················································· 554
Conventions ························································································································· 554
Network topology icons ··········································································································· 555
Support and other resources ·························································· 556
Accessing Hewlett Packard Enterprise Support ············································································ 556
Accessing updates················································································································· 556
Websites ······················································································································· 557
Customer self repair········································································································· 557
Remote support ·············································································································· 557
Documentation feedback ·································································································· 557
Index························································································· 559

1
Configuring basic MPLS
Multiprotocol Label Switching (MPLS) provides connection-oriented label switching over
connectionless IP backbone networks. It integrates both the flexibility of IP routing and the simplicity
of Layer 2 switching.
Overview
MPLS has the following features:
•High speed and efficiency—MPLS uses short- and fixed-length labels to forward packets,
avoiding complicated routing table lookups.
•Multiprotocol support—MPLS resides between the link layer and the network layer. It can
work over various link layer protocols (for example, PPP, frame relay, and Ethernet) to provide
connection-oriented services for various network layer protocols (for example, IPv4, IPv6, and
IPX).
•Good scalability—The connection-oriented switching and multilayer label stack features
enable MPLS to deliver various extended services, such as VPN, traffic engineering, and QoS.
Basic concepts
FEC
MPLS groups packets with the same characteristics (such as packets with the same destination or
service class) into a forwarding equivalence class (FEC). Packets of the same FEC are handled in
the same way on an MPLS network.
Label
A label uniquely identifies an FEC and has local significance.
Figure 1 Format of a label
A label is encapsulated between the Layer 2 header and Layer 3 header of a packet. It is four bytes
long and consists of the following fields:
•Label—20-bit label value.
•TC—3-bit traffic class, used for QoS. It is also called Exp.
•S—1-bit bottom of stack flag.Alabel stack can contain multiple labels. The label nearest to the
Layer 2 header is called the top label, and the label nearest to the Layer 3 header is called the
bottom label. The Sfield is set to 1 if the label is the bottom label and set to 0 if not.
•TTL—8-bit time to live field used for MPLS loop prevention.
LSR
A router that performs MPLS forwarding is a label switching router (LSR).

2
LSP
A label switched path (LSP) is the path along which packets of an FEC travel through an MPLS
network.
An LSP is a unidirectional packet forwarding path. Two neighboring LSRs are called the upstream
LSR and downstream LSR along the direction of an LSP. As shown in Figure 2, LSR B is the
downstream LSR of LSRA, and LSR A is the upstream LSR of LSR B.
Figure 2 Label switched path
LFIB
The Label Forwarding Information Base (LFIB) on an MPLS network functions like the Forwarding
Information Base (FIB) on an IP network. When an LSR receives a labeled packet, it searches the
LFIB to obtain information for forwarding the packet. The information includes the label operation
type, the outgoing label value, and the next hop.
Control plane and forwarding plane
An MPLS node consists of a control plane and a forwarding plane.
•Control plane—Assigns labels, distributes FEC-label mappings to neighbor LSRs, creates the
LFIB, and establishes and removes LSPs.
•Forwarding plane—Forwards packets according to the LFIB.
MPLS network architecture
An MPLS network has the following types of LSRs:
•Ingress LSR—Ingress LSR of packets. It labels packets entering into the MPLS network.
•Transit LSR—Intermediate LSRs in the MPLS network. The transit LSRs on an LSP forward
packets to the egress LSR according to labels.
•Egress LSR—Egress LSR of packets. It removes labels from packets and forwards the
packets to their destination networks.

3
Figure 3 MPLS network architecture
LSP establishment
LSPs include static and dynamic LSPs.
•Static LSP—To establish a static LSP, you must configure an LFIB entry on each LSR along the
LSP. Establishing static LSPs consumes fewer resources than establishing dynamic LSPs, but
static LSPs cannot automatically adapt to network topology changes. Therefore, static LSPs
are suitable for small-scale networks with simple, stable topologies.
•Dynamic LSP—Established by a label distribution protocol (also called an MPLS signaling
protocol).A label distribution protocol classifies FECs, distributes FEC-label mappings, and
establishes and maintains LSPs. Label distribution protocols include protocols designed
specifically for label distribution, such as the Label Distribution Protocol (LDP), and protocols
extended to support label distribution, such as MP-BGP and RSVP-TE.
In this document, the term "label distribution protocols" refers to all protocols for label distribution.
The term "LDP" refers to the RFC 5036 LDP.
A dynamic LSP is established in the following steps:
1. A downstream LSR classifies FECs according to destination addresses.
2. The downstream LSR assigns a label for each FEC, and distributes the FEC-label binding to its
upstream LSR.
3. The upstream LSR establishes an LFIB entry for the FEC according to the binding information.
After all LSRs along the LSP establish an LFIB entry for the FEC, a dynamic LSP is established for
the packets of this FEC.

4
Figure 4 Dynamic LSP establishment
MPLS forwarding
As shown in Figure 5, a packet is forwarded over the MPLS network as follows:
1. Router B (the ingress LSR) receives a packet with no label. Then, it performs the following
operations:
a. Identifies the FIB entry that matches the destination address of the packet.
b. Adds the outgoing label (40, in this example) to the packet.
c. Forwards the labeled packet out of the interface GigabitEthernet 1/1/2 to the next hop LSR
Router C.
2. When receiving the labeled packet, Router C processes the packet as follows:
a. Identifies the LFIB entry that has an incoming label of 40.
b. Uses the outgoing label 50 of the entry to replace label 40 in the packet.
c. Forwards the labeled packet out of the outgoing interface GigabitEthernet 1/1/2 to the next
hop LSR Router D.
3. When receiving the labeled packet, Router D (theegress LSR) processes the packet as follows:
a. Identifies the LFIB entry that has an incoming label of 50.
b. Removes the label from the packet.
c. Forwards the packet out of the outgoing interface GigabitEthernet 1/1/2 to the next hop LSR
Router E.
If the LFIB entry records no outgoing interface or next hop information, Router D performs the
following operations:
d. Identifies the FIB entry by the IP header.
e. Forwards the packet according to the FIB entry.

5
Figure 5 MPLS forwarding
PHP
An egress node must perform two forwarding table lookups to forward a packet:
•Two LFIB lookups (if the packet has more than one label).
•One LFIB lookup and one FIB lookup (if the packet has only one label).
The penultimate hop popping (PHP) feature can pop the label at the penultimate node, so the egress
node only performs one table lookup.
A PHP-capable egress node sends the penultimate node an implicit null label of 3. This label never
appears in the label stack of packets. If an incoming packet matches an LFIB entry containing the
implicit null label, the penultimate node pops the top label and forwards the packet to the egress
node. The egress node directly forwards the packet.
Sometimes, the egress node must use the TC field in the label to perform QoS. To keep the TC
information, you can configure the egress node to send the penultimate node an explicit null label of
0. If an incoming packet matches an LFIB entry containing the explicit null label, the penultimate hop
replaces the top label value with value 0, and forwards the packet to the egress node. The egress
node gets the TC information, pops the label of the packet, and forwards the packet.
Protocols and standards
•RFC 3031, Multiprotocol Label Switching Architecture
•RFC 3032, MPLS Label Stack Encoding
•RFC 5462, Multiprotocol Label Switching (MPLS) Label Stack Entry: "EXP" Field Renamed to
"Traffic Class" Field
MPLS configuration task list
Tasks at a glance
(Required.) Enabling MPLS

6
Tasks at a glance
(Optional.) Setting MPLS MTU
(Optional.) Specifying the label type advertised by egress
(Optional.) Configuring TTL propagation
(Optional.) Enabling sending MPLS TTL-expired messages
(Optional.) Enabling MPLS forwarding statistics
(Optional.) Enabling split horizon for MPLS forwarding
(Optional.) Enabling SNMP notifications for MPLS
Enabling MPLS
Before you enable MPLS, perform the following tasks:
•Configure link layer protocols to ensure connectivity at the link layer.
•Configure IP addresses for interfaces to ensure IP connectivity between neighboring nodes.
•Configure static routes or an IGP protocol to ensure IP connectivity among LSRs.
To enable MPLS:
Step Command Remarks
1. Enter system view. system-view N/A
2. Configure an LSR ID for the
local node. mpls lsr-id lsr-id
By default, no LSR ID is
configured.
An LSR ID must be unique in an
MPLS network and in IP address
format. As a best practice, use
the IP address of a loopback
interface as an LSR ID.
3. Enter the view of the interface
that needs to perform MPLS
forwarding. interface interface-type
interface-number N/A
4. Enable MPLS on the
interface. mpls enable By default, MPLS is disabled on
the interface.
Setting MPLS MTU
MPLS adds the label stack between the link layer header and network layer header of each packet.
To make sure the size of MPLS labeledpackets is smaller than the MTU of an interface, configure an
MPLS MTU on the interface.
MPLS compares each MPLS packet against the interface MPLS MTU. When the packet exceeds the
MPLS MTU:
•If fragmentation is allowed, MPLS performs the following operations:
a. Removes the label stack from the packet.
b. Fragments the IP packet. The length of a fragment is the MPLS MTU minus the length of the
label stack.
c. Adds the label stack to each fragment, and forwards the fragments.
•If fragmentation is not allowed, the LSR drops the packet.

7
To set an MPLS MTU for an interface:
Step Command Remarks
1. Enter system view. system-view N/A
2. Enter interface view. interface interface-type
interface-number N/A
3. Set an MPLS MTU for the
interface. mpls mtu size By default, no MPLS MTU is set
on an interface.
The following applies when an interface handles MPLS packets:
•MPLS packets carrying L2VPN or IPv6 packets are always forwarded by an interface, even if
the length of the MPLS packets exceeds the MPLS MTU of the interface. Whether the
forwarding can succeed depends on the actual forwarding capacity of the interface.
•If the MPLS MTU of an interface is greater than the MTU of the interface, data forwarding might
fail on the interface.
•If you do not configure the MPLS MTU of an interface, fragmentation of MPLS packets is based
on the MTU of the interface without considering MPLS labels. An MPLS fragment might be
larger than the interface MTU and be dropped.
Specifying the label type advertised by egress
In an MPLS network, an egress can advertise the following types of labels:
•Implicit null label with a value of 3.
•Explicit null label with a value of 0.
•Non-null label. The value range for a non-null label is 16 to 79023.
For LSPs established by a label distribution protocol, the label advertised by the egress determines
how the penultimate hop processes a labeled packet.
•If the egress advertises an implicit null label, the penultimate hop directly pops the top label of a
matching packet.
•If the egress advertises an explicit null label, the penultimate hop swaps the top label value of a
matching packet with the explicit null label.
•If the egress advertises a non-null label, the penultimate hop swaps the top label of a matching
packet with the label assigned by the egress.
Configuration guidelines
As a best practice, configure the egress node to advertise an implicit null label to the penultimate hop
if the penultimate hop supports PHP. If you want to simplify packet forwarding on the egress but keep
labels to determine QoS policies, configure the egress node to advertise an explicit null label to the
penultimate hop. Use non-null labels only in particular scenarios. For example, when OAM is
configured on the egress, the egress can get the OAM function entity status only through non-null
labels.
As a penultimate hop, the device accepts the implicit null label, explicit null label, or normal label
advertised by the egress device.
For LDP LSPs, the mpls label advertise command triggers LDP to delete the LSPs established
before the command is executed and re-establishes new LSPs.
For BGP LSPs, the mpls label advertise command takes effect only on the BGP LSPs established
after the command is executed. To apply the new setting to BGP LSPs established before the
command is executed, delete the routes corresponding to the BGP LSPs, and then redistribute the
routes.

8
Configuration procedure
To specify the type of label that the egress node will advertise to the penultimate hop:
Step Command Remarks
1. Enter system view. system-view N/A
2. Specify the label type
advertised by the egress to
the penultimate hop.
mpls label advertise
{ explicit-null | implicit-null |
non-null }
By default, an egress advertises
an implicit null label to the
penultimate hop.
Configuring TTL propagation
When TTLpropagation is enabled, the ingress node copies the TTLvalue of an IP packet to the TTL
field of the label. Each LSR on the LSP decreases the label TTL value by 1. The LSR that pops the
label copies the remaining label TTL value back to the IP TTL of the packet. The IP TTL value can
reflect how many hops the packet has traversed in the MPLS network. The IP tracert facility can
show the real path along which the packet has traveled.
Figure 6 TTL propagation
When TTLpropagation is disabled, the ingress node sets the label TTLto 255. Each LSR on the LSP
decreases the label TTL value by 1. The LSR that pops the label does not change the IP TTL value
when popping the label. Therefore, the MPLS backbone nodes are invisible to user networks, and
the IP tracert facility cannot show the real path in the MPLS network.
Figure 7 Without TTL propagation
Follow these guidelines when you configure TTL propagation:

9
•As a best practice, set the same TTL processing mode on all LSRs of an LSP.
•To enable TTL propagation for a VPN, you must enable it on all PE devices in the VPN. Then,
you can get the same traceroute result (hop count) from those PEs.
To enable TTL propagation:
Step Command Remarks
1. Enter system view. system-view N/A
2. Enable TTL
propagation. mpls ttl propagate { public |
vpn }
By default, TTL propagation is enabled for
public network packets and is disabled for
VPN packets.
This command affects only the propagation
between IP TTL and label TTL. Within an
MPLS network, TTL is always copied
between the labels of an MPLS packet.
Enabling sending MPLS TTL-expired messages
This feature enables an LSR to generate an ICMP TTL-expired message upon receiving an MPLS
packet with a TTLof 1. If the MPLS packet has only one label, the LSR sends the ICMPTTL-expired
message back to the source through IP routing. If the MPLS packet has multiple labels, the LSR
sends it along the LSP to the egress node, which then sends the message back to the source.
To enable sending MPLS TTL-expired messages:
Step Command Remarks
1. Enter system view. system-view N/A
2. Enable sending MPLS
TTL-expired messages. mpls ttl expiration enable By default, this feature is enabled.
Enabling MPLS forwarding statistics
Enabling FTN forwarding statistics
FEC-to-NHLFE map (FTN) entries are FIB entries that contain outgoing labels used for FTN
forwarding. When an LSR receives an unlabeled packet, it searches for the corresponding FTN entry
based on the destination IPaddress. If a match is found, the LSR adds the outgoing label in the FTN
entry to the packet and forwards the labeled packet.
After FTN forwarding statistics is enabled, you can view the statistics from the MIB.
To enable FTN forwarding statistics:
Step Command Remarks
1. Enter system view. system-view N/A
2. Enter RIB view. rib N/A
3. Create a RIB IPv4 address
family and enter RIB IPv4
address family view. address-family ipv4 By default, no RIB IPv4
address family is created.

10
Step Command Remarks
4. Enable the device to
maintain FTN entries in the
RIB. ftn enable By default, the device does not
maintain FTN entries in the
RIB.
5. Enable FTN forwarding
statistics for a destination
network. mpls-forwarding statistics
prefix-list prefix-list-name
By default, FTN forwarding
statistics is disabled for all
destination networks.
Enabling MPLS label forwarding statistics
MPLS label forwarding forwards a labeled packet based on its incoming label.
Perform this task to enable MPLS label forwarding statistics and set the statistics collection interval.
Then, you can use the display mpls lsp verbose command to view MPLS label forwarding
statistics.
To enable MPLS label forwarding statistics:
Step Command Remarks
1. Enter system view. system-view N/A
2. Enable MPLS label
forwarding statistics for
specific LSPs.
mpls statistics { all | [ vpn-instance
vpn-instance-name ] { ipv4
ipv4-address mask-length | ipv6
ipv6-address prefix-length } | static |
te ingress-lsr-id tunnel-id }
By default, MPLS label
forwarding statistics is disabled
for all LSPs.
3. Set the MPLS label
forwarding statistics
collection interval. mpls statistics interval interval By default, MPLS label
forwarding statistics collection
interval is not set.
Enabling split horizon for MPLS forwarding
This feature prevents MPLS packets received from an interface from being forwarded back to that
interface to provide loop-free forwarding.
To enable split horizon for MPLS forwarding:
Step Command Remarks
1. Enter system view. system-view N/A
2. Enable split horizon for
MPLS forwarding. mpls forwarding split-horizon By default, split horizon is
disabled for MPLS forwarding.
Enabling SNMP notifications for MPLS
To report critical MPLS events to an NMS, enable SNMP notifications for MPLS. For MPLS event
notifications to be sent correctly, you must also configure SNMPon the device. For more information
about SNMP configuration, see the network management and monitoring configuration guide for the
device.
To enable SNMP notifications for MPLS: