HPE FlexNetwork 5510 HI Series User manual

HPE FlexNetwork 5510 HI Switch Series
MPLS Configuration Guide
P
art number: 5200-0081b
Software
version: Release 11xx
Document version: 6W102-20171020

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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 ·································································································································4
Protocols and standards ·······································································································5
MPLS configuration task list ·········································································································5
Enabling MPLS ·························································································································5
Configuring MPLS MTU···············································································································6
Specifying the label type advertised by egress ·················································································6
Configuring TTL propagation········································································································7
Enabling sending of MPLS TTL-expired messages ···········································································9
Enabling MPLS forwarding statistics ······························································································9
Enabling SNMP notifications for MPLS ···························································································9
Displaying and maintaining MPLS ·······························································································10
Configuring a static LSP ··································································11
Overview································································································································ 11
Configuration prerequisites ········································································································11
Configuration procedure············································································································ 11
Displaying static LSPs···············································································································12
Static LSP configuration example································································································12
Network requirements ········································································································12
Configuration restrictions and guidelines ················································································12
Configuration procedure ····································································································· 13
Verifying the configuration···································································································14
Configuring LDP ············································································15
Overview································································································································ 15
Terminology····················································································································· 15
LDP messages ·················································································································15
LDP operation ··················································································································16
Label distribution and control ·······························································································17
LDP GR ·························································································································· 19
LDP NSR························································································································· 20
LDP-IGP synchronization····································································································21
LDP FRR·························································································································21
Protocols·························································································································22
LDP configuration task list·········································································································· 22
Enabling LDP·························································································································· 23
Enabling LDP globally ········································································································23
Enabling LDP on an interface·······························································································23
Configuring Hello parameters ·····································································································24
Configuring LDP session parameters ···························································································24
Configuring LDP backoff············································································································25
Configuring LDP MD5 authentication····························································································26
Configuring an LSP generation policy···························································································26
Configuring the LDP label distribution control mode·········································································27
Configuring a label advertisement policy·······················································································27
Configuring a label acceptance policy···························································································28
Configuring LDP loop detection··································································································· 29
Configuring LDP session protection ·····························································································30
Configuring LDP GR·················································································································31
Configuring LDP NSR···············································································································31
Configuring LDP-IGP synchronization ·························································································· 31

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Configuring LDP-OSPF synchronization·················································································31
Configuring LDP-ISIS synchronization ···················································································32
Configuring LDP FRR ··············································································································· 33
Resetting LDP sessions ············································································································33
Enabling SNMP notifications for LDP ···························································································33
Displaying and maintaining LDP·································································································· 34
LDP configuration examples······································································································· 34
LDP LSP configuration example ···························································································34
Label acceptance control configuration example ······································································38
Label advertisement control configuration example···································································42
LDP FRR configuration example···························································································47
Configuring MPLS TE ·····································································51
Overview································································································································ 51
TE and MPLS TE ·············································································································· 51
MPLS TE basic concepts ····································································································51
Static CRLSP establishment································································································51
Dynamic CRLSP establishment····························································································51
Traffic forwarding ··············································································································53
Make-before-break ············································································································54
Route pinning··················································································································· 55
Tunnel reoptimization·········································································································55
Automatic bandwidth adjustment ··························································································55
CRLSP backup················································································································· 56
FRR ······························································································································· 56
DiffServ-aware TE············································································································· 57
Bidirectional MPLS TE tunnel·······························································································59
Protocols and standards ·····································································································59
MPLS TE configuration task list···································································································60
Enabling MPLS TE···················································································································61
Configuring a tunnel interface·····································································································61
Configuring DS-TE··················································································································· 61
Configuring an MPLS TE tunnel to use a static CRLSP····································································62
Configuring an MPLS TE tunnel to use a dynamic CRLSP································································63
Configuration task list·········································································································63
Configuring MPLS TE attributes for a link ···············································································63
Advertising link TE attributes by using IGP TE extension ···························································64
Configuring MPLS TE tunnel constraints ················································································65
Establishing an MPLS TE tunnel by using RSVP-TE·································································67
Controlling CRLSP path selection ·························································································67
Controlling MPLS TE tunnel setup ························································································69
Configuring traffic forwarding······································································································72
Configuring static routing to direct traffic to an MPLS TE tunnel···················································72
Configuring automatic route advertisement to direct traffic to an MPLS TE tunnel····························72
Configuring a bidirectional MPLS TE tunnel···················································································73
Configuring CRLSP backup········································································································ 74
Configuring MPLS TE FRR ········································································································ 74
Enabling FRR··················································································································· 75
Configuring a bypass tunnel on the PLR·················································································75
Configuring node fault detection ···························································································79
Configuring the optimal bypass tunnel selection interval ····························································79
Displaying and maintaining MPLS TE···························································································79
MPLS TE configuration examples································································································80
Establishing an MPLS TE tunnel over a static CRLSP·······························································80
Establishing an MPLS TE tunnel with RSVP-TE·······································································85
Establishing an inter-AS MPLS TE tunnel with RSVP-TE ···························································91
Bidirectional MPLS TE tunnel configuration example·································································98
CRLSP backup configuration example················································································· 104
Manual bypass tunnel for FRR configuration example····························································· 108
Auto FRR configuration example ························································································ 114
IETF DS-TE configuration example ····················································································· 120
Troubleshooting MPLS TE······································································································· 127

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No TE LSA generated ······································································································ 127
Configuring a static CRLSP···························································· 128
Overview······························································································································ 128
Configuration procedure·········································································································· 128
Displaying static CRLSPs ········································································································ 129
Static CRLSP configuration example·························································································· 129
Network requirements ······································································································ 129
Configuration procedure ··································································································· 130
Verifying the configuration································································································· 132
Configuring RSVP········································································ 135
Overview······························································································································ 135
RSVP messages············································································································· 135
CRLSP setup procedure ··································································································· 136
RSVP refresh mechanism ································································································· 136
RSVP authentication········································································································ 137
RSVP GR······················································································································ 137
Protocols and standards ··································································································· 138
RSVP configuration task list ····································································································· 138
Enabling RSVP ····················································································································· 138
Configuring RSVP refresh········································································································ 138
Configuring RSVP Srefresh and reliable RSVP message delivery ···················································· 139
Configuring RSVP hello extension····························································································· 139
Configuring RSVP authentication ······························································································ 140
Specifying a DSCP value for outgoing RSVP packets···································································· 141
Configuring RSVP GR············································································································· 142
Enabling BFD for RSVP ·········································································································· 142
Displaying and maintaining RSVP ····························································································· 142
RSVP configuration examples ·································································································· 143
Establishing an MPLS TE tunnel with RSVP-TE····································································· 143
RSVP GR configuration example························································································ 147
Configuring tunnel policies ····························································· 150
Overview······························································································································ 150
Configuring a tunnel policy······································································································· 150
Configuration guidelines ··································································································· 150
Configuration procedure ··································································································· 151
Displaying tunnel information···································································································· 152
Tunnel policy configuration examples························································································· 152
Preferred tunnel configuration example················································································ 152
Exclusive tunnel configuration example················································································ 152
Tunnel selection order configuration example········································································ 153
Preferred tunnel and tunnel selection order configuration example············································· 153
Configuring MPLS L3VPN······························································ 155
Overview······························································································································ 155
Basic MPLS L3VPN architecture ························································································ 155
MPLS L3VPN concepts ···································································································· 155
MPLS L3VPN route advertisement······················································································ 157
MPLS L3VPN packet forwarding························································································· 158
MPLS L3VPN networking schemes····················································································· 159
Inter-AS VPN·················································································································· 161
Carrier's carrier··············································································································· 165
Nested VPN··················································································································· 167
HoVPN·························································································································· 168
OSPF VPN extension······································································································· 169
BGP AS number substitution ····························································································· 171
MPLS L3VPN FRR·········································································································· 172
Protocols and standards ··································································································· 174
MPLS L3VPN configuration task list··························································································· 174
Configuring basic MPLS L3VPN································································································ 175

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Configuration prerequisites································································································ 175
Configuring VPN instances································································································ 175
Configuring routing between a PE and a CE·········································································· 177
Configuring routing between PEs························································································ 181
Configuring BGP VPNv4 route control·················································································· 182
Configuring inter-AS VPN ········································································································ 183
Configuring inter-AS option A····························································································· 183
Configuring inter-AS option B····························································································· 184
Configuring inter-AS option C····························································································· 185
Configuring nested VPN·········································································································· 188
Configuring HoVPN················································································································ 189
Configuring an OSPF sham link ································································································ 190
Configuring a loopback interface························································································· 190
Redistributing the loopback interface route············································································ 191
Creating a sham link ········································································································ 191
Specifying the VPN label processing mode on the egress PE·························································· 191
Configuring BGP AS number substitution···················································································· 192
Configuring MPLS L3VPN FRR································································································· 192
Enabling SNMP notifications for MPLS L3VPN············································································· 194
Enabling logging for BGP route flapping······················································································ 194
Displaying and maintaining MPLS L3VPN··················································································· 195
MPLS L3VPN configuration examples ························································································ 196
Configuring basic MPLS L3VPN ························································································· 196
Configuring a hub-spoke network························································································ 202
Configuring MPLS L3VPN inter-AS option A·········································································· 209
Configuring MPLS L3VPN inter-AS option B·········································································· 213
Configuring MPLS L3VPN inter-AS option C ········································································· 218
Configuring MPLS L3VPN carrier's carrier ············································································ 225
Configuring nested VPN ··································································································· 233
Configuring HoVPN ········································································································· 242
Configuring an OSPF sham link·························································································· 249
Configuring BGP AS number substitution ············································································· 253
Configuring MPLS L3VPN FRR through VPNv4 route backup for a VPNv4 route ·························· 257
Configuring MPLS L3VPN FRR through VPNv4 route backup for an IPv4 route···························· 259
Configuring MPLS L3VPN FRR through IPv4 route backup for a VPNv4 route······························ 261
Configuring IPv6 MPLS L3VPN······················································· 264
Overview······························································································································ 264
IPv6 MPLS L3VPN packet forwarding·················································································· 264
IPv6 MPLS L3VPN routing information advertisement····························································· 265
IPv6 MPLS L3VPN network schemes and functions································································ 265
Protocols and standards ··································································································· 265
IPv6 MPLS L3VPN configuration task list ···················································································· 266
Configuring basic IPv6 MPLS L3VPN························································································· 266
Configuring VPN instances································································································ 266
Configuring routing between a PE and a CE·········································································· 268
Configuring routing between PEs························································································ 274
Configuring BGP VPNv6 route control·················································································· 274
Configuring inter-AS IPv6 VPN ································································································· 275
Configuring inter-AS IPv6 VPN option A··············································································· 276
Configuring inter-AS IPv6 VPN option C··············································································· 276
Configuring an OSPFv3 sham link····························································································· 277
Configuring a loopback interface························································································· 277
Redistributing the loopback interface address········································································ 277
Creating a sham link ········································································································ 278
Enabling logging for BGP route flapping······················································································ 278
Displaying and maintaining IPv6 MPLS L3VPN ············································································ 278
IPv6 MPLS L3VPN configuration examples ················································································· 280
Configuring IPv6 MPLS L3VPNs························································································· 280
Configuring IPv6 MPLS L3VPN inter-AS option A··································································· 286
Configuring IPv6 MPLS L3VPN inter-AS option C··································································· 291
Configuring IPv6 MPLS L3VPN carrier's carrier······································································ 297

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Configuring an OSPFv3 sham link ······················································································ 304
Configuring MPLS L2VPN······························································ 310
Overview······························································································································ 310
Basic concepts of MPLS L2VPN························································································· 310
MPLS L2VPN network models ··························································································· 311
PW redundancy ·············································································································· 312
Multi-segment PW··········································································································· 313
VCCV ··························································································································· 314
MPLS L2VPN configuration task list··························································································· 315
Enabling L2VPN ···················································································································· 315
Configuring an AC·················································································································· 316
Configuring a cross-connect····································································································· 316
Configuring a PW··················································································································· 317
Configuring a PW class ···································································································· 317
Configuring a static PW ···································································································· 317
Configuring an LDP PW···································································································· 317
Configuring a BGP PW····································································································· 318
Configuring a remote CCC connection················································································· 320
Binding an AC to a cross-connect······························································································ 320
Configuring PW redundancy····································································································· 321
Configuring static PW redundancy ······················································································ 321
Configuring LDP PW redundancy ······················································································· 322
Displaying and maintaining MPLS L2VPN··················································································· 322
MPLS L2VPN configuration examples ························································································ 323
Configuring a static PW ···································································································· 323
Configuring an LDP PW···································································································· 327
Configuring a BGP PW····································································································· 331
Configuring a remote CCC connection················································································· 335
Configuring LDP PW redundancy ······················································································· 338
Configuring an intra-domain multi-segment PW ····································································· 344
Configuring an inter-domain multi-segment PW ····································································· 347
Configuring VPLS········································································· 355
Overview······························································································································ 355
Basic VPLS architecture ··································································································· 355
VPLS implementation······································································································· 356
H-VPLS························································································································· 358
VPLS configuration task list······································································································ 360
Enabling L2VPN ···················································································································· 361
Configuring an AC·················································································································· 361
Configuring a VSI··················································································································· 362
Configuring a PW··················································································································· 362
Configuring a PW class ···································································································· 362
Configuring a static PW ···································································································· 362
Configuring an LDP PW···································································································· 363
Configuring a BGP PW····································································································· 363
Configuring a BGP auto-discovery LDP PW·········································································· 365
Binding an AC to a VSI············································································································ 367
Configuring UPE dual homing··································································································· 367
Configuring static PW redundancy ······················································································ 368
Configuring LDP PW redundancy ······················································································· 368
Configuring MAC address learning ···························································································· 369
Displaying and maintaining VPLS······························································································ 369
VPLS configuration examples··································································································· 370
Static PW configuration example ························································································ 370
LDP PW configuration example·························································································· 375
BGP PW configuration example ························································································· 377
BGP auto-discovery LDP PW configuration example······························································· 382
H-VPLS using access configuration example········································································· 386
H-VPLS UPE dual homing configuration example··································································· 390

vi
Configuring MPLS OAM ································································ 397
Overview······························································································································ 397
MPLS ping····················································································································· 397
MPLS tracert·················································································································· 397
BFD for MPLS ················································································································ 397
Periodic MPLS tracert ······································································································ 398
Protocols and standards·········································································································· 398
Configuring MPLS OAM for LSP tunnels····················································································· 398
Configuring MPLS ping for LSPs ························································································ 398
Configuring MPLS tracert for LSPs······················································································ 399
Configuring BFD for LSPs ································································································· 399
Configuring periodic MPLS tracert for LSPs ·········································································· 400
Configuring MPLS OAM for MPLS TE tunnels·············································································· 400
Configuring MPLS OAM for a PW······························································································ 401
Configuring MPLS ping for a PW ························································································ 401
Configuring BFD for a PW································································································· 401
Displaying MPLS OAM············································································································ 405
MPLS OAM configuration examples··························································································· 405
BFD for LSP configuration example····················································································· 405
BFD for PW configuration example······················································································ 407
Configuring MCE·········································································· 413
MPLS L3VPN overview··········································································································· 413
Basic MPLS L3VPN architecture ························································································ 413
MPLS L3VPN concepts ···································································································· 413
MCE overview······················································································································· 415
MCE configuration task list······································································································· 416
Configuring VPN instances ······································································································ 416
Creating a VPN instance··································································································· 416
Associating a VPN instance with an interface ········································································ 417
Configuring route related attributes for a VPN instance···························································· 417
Configuring routing on an MCE································································································· 418
Configuring routing between an MCE and a VPN site······························································ 418
Configuring routing between an MCE and a PE ····································································· 423
Displaying and maintaining MCE······························································································· 427
MCE configuration examples···································································································· 428
Configuring the MCE that uses OSPF to advertise VPN routes to the PE ···································· 428
Configuring the MCE that uses EBGP to advertise VPN routes to the PE ···································· 433
Configuring IPv6 MCE··································································· 438
Overview······························································································································ 438
IPv6 MCE configuration task list································································································ 438
Configuring VPN instances ······································································································ 438
Creating a VPN instance··································································································· 438
Associating a VPN instance with an interface ········································································ 439
Configuring route related attributes for a VPN instance···························································· 439
Configuring routing on an MCE································································································· 440
Configuring routing between an MCE and a VPN site······························································ 441
Configuring routing between an MCE and a PE ····································································· 445
Displaying and maintaining IPv6 MCE························································································ 449
IPv6 MCE configuration example······························································································· 449
Document conventions and icons ···················································· 457
Conventions ························································································································· 457
Network topology icons ··········································································································· 458
Support and other resources ·························································· 459
Accessing Hewlett Packard Enterprise Support ············································································ 459
Accessing updates················································································································· 459
Websites ······················································································································· 460
Customer self repair········································································································· 460

vii
Remote support ·············································································································· 460
Documentation feedback ·································································································· 460
Index························································································· 462

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.
In this chapter, the term "interface"refers to a Layer 3 interface. It can be a VLAN interface or a Layer
3 Ethernet interface. Layer 3 Ethernet interfaces refer to the Ethernet interfaces that operate in Layer
3 mode. For information about switching the Ethernet interface operating mode, see Layer 2—LAN
Switching Configuration Guide.
Overview
MPLS has the following advantages:
•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,ATM, 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. A label stack can have 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 routing loop prevention.
TC
0
S
19 2223 31
Label TTL
Layer 2 header Layer 3 headerLabel Layer 3 data

2
LSR
A router that performs MPLS forwarding is a label switching router (LSR).
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. In Figure 2, LSR B is the downstream LSR
of LSR A, 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, such as 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
Figure 3 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.
LSR A
LSR B LSR C
LSR D
LSP
LSP
LSP
Ingress LSR LSP Egress LSR
Transit LSR
IP network IP network
MPLS network

3
•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.
LSP establishment
LSPs include static and dynamic LSPs.
•Static LSP—To establish a static LSP, you must configure an LFIB entry on eachLSR 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.
Figure 4 Dynamic LSP establishment
LSR A LSR B LSR D
LSR C
LSR E LSR F LSR G
LSR H
Ingress Egress
LSP
Label mapping

4
MPLS forwarding
Figure 5 MPLS forwarding
As shown in Figure 5, a packet is forwarded over the MPLS network in the following steps:
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 VLAN-interface 20 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 VLAN-interface 30 to the nexthop
LSR Router D.
3. When receiving the labeled packet, Router D (the egress) 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 VLAN-interface 40 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:
a. Identifies the FIB entry by the IP header.
b. Forwards the packet according to the FIB entry.
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).
Router A Router B
Ingress Router C Router D Egress Router E
Router F
IP:10.1.1.1
MPLS network
IP:10.1.1.1
40 IP:10.1.1.1 50 IP:10.1.1.1
Vlan10 Vlan20 Vlan20 Vlan30 Vlan30 Vlan40
FIB table
LFIB table
LFIB table
NexthopDest Out intOut label
10.1.0.0Vlan2040 Router C
Nexthop
Router D Out int
Vlan30
Out label
50
Oper
Swap
In label
40
Nexthop
Router E Out int
Vlan40
Out label
--
Oper
Pop
In label
50

5
•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 comprising the
implicit null label, the penultimate node pops the top label of the packet and forwards the packet to
the egress LSR. The egress LSR 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 comprising the explicit null label, the penultimate hop
replaces the value of the top label 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
(Optional.) Configuring MPLS MTU
(Optional.) Specifying the label type advertised by egress
(Optional.) Configuring TTL propagation
(Optional.) Enabling sending of MPLS TTL-expired messages
(Optional.) Enabling MPLS forwarding statistics
(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

6
Step
Command
Remarks
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 for the interface. mpls enable By default, MPLS is disabled on an
interface.
Configuring MPLS MTU
MPLS inserts the label stack between the link layer header and network layer header ofeach packet.
To make sure the size of MPLS labeled packets 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 does the following:
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.
To configure 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. Configure an MPLS MTU for
the interface. mpls mtu value
By default, no MPLS MTU is
configured 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.

7
•Non-null label. The value range for a non-null label is 16 to 1048575.
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 (normal label), the penultimate hop swaps the top label
of a matching packet with the specific label assigned by the egress.
Configuration guidelines
When you specify the label type advertised by egress, follow these restrictions and guidelines:
•If the penultimate hop supports PHP, configure the egress to advertise an implicit null label to
the penultimate hop as a best practice.
•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 for 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.
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 TTL propagation is enabled, the ingress node copies the TTL value 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 TTLvalue back to the IP TTL of the packet, so 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.

8
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:
•Enable or disable TTL propagation before you configure MPLS services. If you change the
propagation configuration after the MPLS service configuration, you must reboot the device.
•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, so that
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 only
for public-network 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.
Ingress Egress
LSR D
TTL TTLIP TTL Label TTL
TTL 253 TTL 252 TTL 252 TTL 249 TTL 248
TTL 252 TTL 250
Copy the TTL value
TTL 251
TTL 252
LSR A LSR B LSR C LSR E
TTL 249
TTL 249
Copy the label TTL value to the IP
packet and pops the label at the
penultimate hop
Ingress Egress
LSR D
TTL TTLIP TTL Label TTL
TTL 3 TTL 2 TTL 2 TTL 2 TTL 1
TTL 255 TTL 253
TTL 254
TTL 2
LSR A LSR B LSR C LSR E

9
Enabling sending of 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 ICMP TTL-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 of MPLS TTL-expired messages:
Step
Command
Remarks
1. Enter system view. system-view N/A
2.
Enable sending of MPLS
TTL-expired messages. mpls ttl expiration enable
By default, this function is
enabled.
Enabling MPLS 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-destination mask-length | ipv6
ipv6-destination 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, the MPLS label
forwarding statistics collection
interval is not set.
Enabling SNMP notifications for MPLS
This feature enables MPLS to generate SNMP notifications. The generated SNMP notifications are
sent to the SNMP module.
For more information about SNMP notifications, see Network Management and Monitoring
Configuration Guide.
To enable SNMP notifications for MPLS:
Step
Command
Remarks
1. Enter system view. system-view N/A
2.
Enable SNMP
notifications for MPLS. snmp-agent trap enable mpls By default, SNMP notifications for
MPLS are enabled.

10
Displaying and maintaining MPLS
Execute display commands in any view and reset commands in user view.
Task
Command
Display MPLS interface information. display mpls interface [ interface-type interface-number ]
Display usage information about MPLS
labels. display mpls label { label-value1 [ to label-value2 ] | all }
Display LSP information.
display mpls lsp [ egress | in-label label-value | ingress |
outgoing-interface interface-type interface-number | protocol
{bgp | ldp | local | rsvp-te | static | static-cr } | transit ]
[ vpn-instance vpn-instance-name ] [ ipv4-dest mask-length |
ipv6
[ ipv6-dest prefix-length ] ] [
verbose
]
Display MPLS Nexthop Information
Base (NIB) information. display mpls nib [ nib-id ]
Display usage information about NIDs. display mpls nid [ nid-value1 [ to nid-value2 ] ]
Display LSP statistics. display mpls lsp statistics
Display MPLS summary information. display mpls summary
Display ILM entries. display mpls forwarding ilm [ label ] [ slot slot-number ]
Display NHLFE entries. display mpls forwarding nhlfe [ nid ] [ slot slot-number ]
Clear MPLS forwarding statistics for the
specified LSPs.
reset mpls statistics { all | [ vpn-instance vpn-instance-name ]
{ ipv4 ipv4-destination mask-length | ipv6 ipv6-destination
prefix-length } |
static
|
te
ingress-lsr-id tunnel-id }

11
Configuring a static LSP
Overview
A static label switched path (LSP) is established by manually specifying the incoming label and
outgoing label on each node (ingress, transit, or egress node) of the forwarding path.
Static LSPs consume fewer resources, but they cannot automatically adapt to network topology
changes. Therefore, static LSPs are suitable for small and stable networks with simple topologies.
Follow these guidelines to establish a static LSP:
•The ingress node performs the following operations:
a. Determines an FEC for a packet according to the destination address.
b. Adds the label for that FEC into the packet.
c. Forwards the packet to the next hop or out of the outgoing interface.
Therefore, on the ingress node, you must specify the outgoing label for the destination address
(the FEC) and the next hop or the outgoing interface.
•A transit node swaps the label carried in a received packet with a specific label, and forwards
the packet to the next hop or out of the outgoing interface. Therefore, on each transit node, you
must specify the incoming label, the outgoing label, and the next hop or the outgoing interface.
•If the penultimate hop popping function is not configured, an egress node pops the incoming
label of a packet, and performs label forwarding according to the inner label or IP forwarding.
Therefore, on the egress node, you only need to specify the incoming label.
•The outgoing label specified on an LSR must be the same as the incoming label specified on
the directly connected downstream LSR.
Configuration prerequisites
Before you configure a static LSP, perform the following tasks:
•Identify the ingress node, transit nodes, and egress node of the LSP.
•Enable MPLS on all interfaces that participate in MPLS forwarding. For more information, see
"Configuring basic MPLS."
•Make sure the ingress node has a route to the destination address of the LSP. This is not
required on transit and egress nodes.
Configuration procedure
To configure a static LSP:
Step
Command
Remarks
1. Enter system view. system-view N/A
2.
Configure the
ingress node of the
static LSP.
static-lsp ingress lsp-name destination
dest-addr { mask | mask-length } { nexthop
next-hop-addr | outgoing-interface
interface-type interface-number } out-label
out-label
If you specify a next hop for the
static LSP, make sure the ingress
node has an active route to the
specified next hop address.
3.
Configure the
transit node of the static-lsp transit lsp-name in-label
in-label { nexthop next-hop-addr |
If you specify a next hop for the
static LSP, make sure the transit