HP 10500 series User manual

HPE FlexNetwork 10500 Switch Series
MPLS Configuration Guide
Part number: 5200
-1902a
Software
version: 10500-CMW710-R7557P01
Document version: 6W101-20171020

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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····························································································································································5
Protocols and standards ····························································································································5
Restrictions and guidelines for basic MPLS·······································································································5
MPLS configuration task list·······························································································································6
Enabling MPLS ··················································································································································6
Setting MPLS MTU ············································································································································7
Specifying the label type advertised by egress··································································································8
Configuring TTL propagation ·····························································································································8
Enabling sending MPLS TTL-expired messages·····························································································10
Enabling SNMP notifications for MPLS············································································································10
Displaying and maintaining MPLS ···················································································································10
Configuring a static LSP ··············································································12
Overview··························································································································································12
Restrictions and guidelines for static LSP········································································································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·························································································································22
LDP FRR··················································································································································23
LDP over MPLS TE··································································································································24
Protocols··················································································································································25
Restrictions and guidelines for LDP·················································································································25
LDP configuration task list································································································································25
Enabling LDP···················································································································································26
Enabling LDP globally······························································································································26
Enabling LDP on an interface ··················································································································26
Configuring Hello parameters ··························································································································27
Configuring LDP session parameters ··············································································································27
About LDP session parameters ···············································································································27
Restrictions and guidelines······················································································································28
Configuring LDP backoff··································································································································30
Configuring LDP MD5 authentication···············································································································30
Configuring LDP to redistribute BGP unicast routes························································································31
Configuring an LSP generation policy··············································································································31
Configuring the LDP label distribution control mode························································································32
Configuring a label advertisement policy ·········································································································32

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Configuring a label acceptance policy ·············································································································33
Configuring LDP loop detection ·······················································································································34
Configuring LDP session protection·················································································································35
Configuring LDP GR ········································································································································36
Configuring LDP NSR······································································································································36
Configuring LDP-IGP synchronization ·············································································································36
Configuring LDP-OSPF synchronization··································································································36
Configuring LDP IS-IS synchronization····································································································38
Configuring LDP FRR ······································································································································38
Setting a DSCP value for outgoing LDP packets·····························································································38
Resetting LDP sessions···································································································································39
Enabling SNMP notifications for LDP···············································································································39
Displaying and maintaining LDP······················································································································39
IPv4 LDP configuration examples····················································································································40
LDP LSP configuration example··············································································································40
Label acceptance control configuration example·····················································································44
Label advertisement control configuration example·················································································48
LDP FRR configuration example··············································································································53
IPv6 LDP configuration examples····················································································································56
IPv6 LDP LSP configuration example······································································································56
IPv6 label acceptance control configuration example··············································································61
IPv6 label advertisement control configuration example··········································································65
Configuring MPLS TE··················································································72
Overview··························································································································································72
TE and MPLS TE·····································································································································72
MPLS TE basic concepts·························································································································72
Static CRLSP establishment····················································································································72
Dynamic CRLSP establishment···············································································································72
CRLSP establishment using PCE path calculation··················································································74
Traffic forwarding ·····································································································································75
Make-before-break···································································································································76
Route pinning···········································································································································77
Tunnel reoptimization·······························································································································77
CRLSP backup·········································································································································77
FRR··························································································································································77
DiffServ-aware TE····································································································································78
Bidirectional MPLS TE tunnel ··················································································································80
Protocols and standards ··························································································································81
Restrictions and guidelines for MPLS TE·········································································································81
MPLS TE configuration task list·······················································································································81
Enabling MPLS TE···········································································································································83
Configuring a tunnel interface··························································································································83
Configuring DS-TE···········································································································································84
Configuring an MPLS TE tunnel to use a static CRLSP ··················································································84
Configuring an MPLS TE tunnel to use a dynamic CRLSP ·············································································85
Configuration task list·······························································································································85
Configuring MPLS TE attributes for a link································································································86
Advertising link TE attributes by using IGP TE extension········································································86
Configuring MPLS TE tunnel constraints·································································································87
Establishing an MPLS TE tunnel by using RSVP-TE···············································································89
Controlling CRLSP path selection············································································································89
Controlling MPLS TE tunnel setup···········································································································92
Configuring an MPLS TE tunnel to use a CRLSP calculated by PCEs ···························································93
Configuring a PCE ···································································································································93
Discovering PCEs····································································································································93
Establishing a CRLSP by using the path calculated by PCEs·································································94
Establishing a backup CRLSP by using the path calculated by PCEs·····················································94
Configuring PCEP session parameters····································································································94
Configuring traffic forwarding···························································································································95
Configuring static routing to direct traffic to an MPLS TE tunnel······························································95
Configuring automatic route advertisement to direct traffic to an MPLS TE tunnel··································95

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Configuring a bidirectional MPLS TE tunnel ····································································································96
Configuring CRLSP backup·····························································································································97
Configuring MPLS TE FRR······························································································································98
Enabling FRR···········································································································································98
Configuring a bypass tunnel on the PLR··································································································98
Configuring node fault detection ············································································································102
Setting the optimal bypass tunnel selection interval ··············································································102
Enabling SNMP notifications for MPLS TE····································································································103
Displaying and maintaining MPLS TE············································································································103
MPLS TE configuration examples··················································································································104
Establishing an MPLS TE tunnel over a static CRLSP··········································································104
Establishing an MPLS TE tunnel with RSVP-TE····················································································109
Establishing an inter-AS MPLS TE tunnel with RSVP-TE······································································114
Establishing an inter-area MPLS TE tunnel over a CRLSP calculated by PCEs···································121
Bidirectional MPLS TE tunnel configuration example············································································126
CRLSP backup configuration example ··································································································132
Manual bypass tunnel for FRR configuration example ··········································································136
Auto FRR configuration example···········································································································142
IETF DS-TE configuration example ·······································································································148
Troubleshooting MPLS TE·····························································································································155
No TE LSA generated····························································································································155
Configuring a static CRLSP·······································································156
Overview························································································································································156
Prerequisites for static CRLSP·······················································································································156
Restrictions and guidelines for static CRLSP·································································································156
Configuration procedure·································································································································157
Displaying static CRLSPs ······························································································································157
Static CRLSP configuration example·············································································································157
Network requirements····························································································································157
Configuration procedure·························································································································158
Verifying the configuration······················································································································160
Configuring RSVP······················································································163
Overview························································································································································163
RSVP messages····································································································································163
CRLSP setup procedure························································································································164
RSVP refresh mechanism······················································································································164
RSVP authentication······························································································································165
RSVP GR···············································································································································165
Protocols and standards ························································································································166
Restrictions and guidelines for RSVP············································································································166
RSVP configuration task list···························································································································166
Enabling RSVP ··············································································································································166
Configuring RSVP refresh······························································································································167
Configuring RSVP Srefresh and reliable RSVP message delivery································································167
Configuring RSVP hello extension·················································································································167
Configuring RSVP authentication ··················································································································168
Setting a DSCP value for outgoing RSVP packets························································································170
Configuring RSVP GR····································································································································170
Enabling BFD for RSVP·································································································································170
Displaying and maintaining RSVP ·················································································································171
RSVP configuration examples ·······················································································································171
Establishing an MPLS TE tunnel with RSVP-TE····················································································171
RSVP GR configuration example···········································································································177
Configuring tunnel policies·········································································180
Overview························································································································································180
Configuring a tunnel policy·····························································································································180
Configuration guidelines·························································································································180
Configuration procedure·························································································································181
Displaying tunnel information·························································································································181

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Tunnel policy configuration examples············································································································182
Exclusive tunnel configuration example·································································································182
Preferred tunnel and tunnel selection order configuration example·······················································182
Configuring MPLS L3VPN ·········································································185
Overview························································································································································185
Basic MPLS L3VPN architecture ···········································································································185
MPLS L3VPN concepts··························································································································185
MPLS L3VPN route advertisement········································································································187
MPLS L3VPN packet forwarding············································································································188
MPLS L3VPN networking schemes·······································································································189
Inter-AS VPN··········································································································································191
OSPF VPN extension·····························································································································195
BGP AS number substitution and SoO attribute····················································································198
MPLS L3VPN FRR·································································································································199
ECMP VPN route redistribution··············································································································201
Protocols and standards ························································································································201
Restrictions and guidelines for MPLS L3VPN································································································201
MPLS L3VPN configuration task list··············································································································201
Configuring basic MPLS L3VPN····················································································································202
Configuration prerequisites····················································································································202
Configuring VPN instances····················································································································202
Configuring routing between a PE and a CE ·························································································204
Configuring routing between PEs···········································································································209
Configuring BGP VPNv4 route control···································································································209
Configuring inter-AS VPN ······························································································································211
Configuring inter-AS option A·················································································································211
Configuring inter-AS option B·················································································································212
Configuring inter-AS option C ················································································································213
Configuring an OSPF sham link·····················································································································215
Configuring a loopback interface············································································································216
Redistributing the loopback interface address·······················································································216
Creating a sham link ······························································································································216
Specifying the VPN label processing mode on the egress PE ······································································217
Configuring BGP AS number substitution and SoO attribute·········································································217
Configuring MPLS L3VPN FRR·····················································································································218
Configuring BGP RT filtering··························································································································219
About BGP RT filtering···························································································································219
Procedure···············································································································································220
Configuring route replication··························································································································220
About route replication···························································································································220
Procedure···············································································································································220
Enabling ECMP VPN route redistribution·······································································································221
About ECMP VPN route redistribution···································································································221
Procedure···············································································································································221
Enabling SNMP notifications for MPLS L3VPN ·····························································································222
Enabling logging for BGP route flapping········································································································222
Displaying and maintaining MPLS L3VPN·····································································································223
MPLS L3VPN configuration examples···········································································································224
Configuring basic MPLS L3VPN············································································································224
Configuring a hub-spoke network ··········································································································230
Configuring MPLS L3VPN inter-AS option A ·························································································236
Configuring MPLS L3VPN inter-AS option B ·························································································241
Configuring MPLS L3VPN inter-AS option C·························································································246
Configuring an OSPF sham link·············································································································253
Configuring BGP AS number substitution······························································································257
Configuring BGP AS number substitution and SoO attribute·································································261
Configuring MPLS L3VPN FRR through VPNv4 route backup for a VPNv4 route ································263
Configuring MPLS L3VPN FRR through VPNv4 route backup for an IPv4 route ··································265
Configuring MPLS L3VPN FRR through IPv4 route backup for a VPNv4 route ····································267

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Configuring IPv6 MPLS L3VPN ·································································270
Overview························································································································································270
IPv6 MPLS L3VPN packet forwarding ···································································································270
IPv6 MPLS L3VPN routing information advertisement ··········································································271
IPv6 MPLS L3VPN network schemes and features···············································································271
Protocols and standards ························································································································271
Configuration restrictions and guidelines·······································································································272
IPv6 MPLS L3VPN configuration task list······································································································272
Configuring basic IPv6 MPLS L3VPN············································································································272
Configuration prerequisites····················································································································272
Configuring VPN instances····················································································································272
Configuring routing between a PE and a CE ·························································································274
Configuring routing between PEs···········································································································280
Configuring BGP VPNv6 route control···································································································281
Configuring inter-AS IPv6 VPN······················································································································282
Configuring inter-AS IPv6 VPN option A································································································283
Configuring inter-AS IPv6 VPN option C································································································283
Configuring an OSPFv3 sham link·················································································································284
Configuring a loopback interface············································································································284
Redistributing the loopback interface address·······················································································284
Creating a sham link ······························································································································285
Configuring BGP AS number substitution and SoO attribute·········································································285
Enabling logging for BGP route flapping········································································································286
Displaying and maintaining IPv6 MPLS L3VPN·····························································································286
IPv6 MPLS L3VPN configuration examples···································································································287
Configuring IPv6 MPLS L3VPNs············································································································287
Configuring a hub-spoke network ··········································································································293
Configuring IPv6 MPLS L3VPN inter-AS option A·················································································300
Configuring IPv6 MPLS L3VPN inter-AS option C·················································································305
Configuring an OSPFv3 sham link·········································································································311
Configuring BGP AS number substitution······························································································315
Configuring BGP AS number substitution and SoO attribute·································································320
Configuring MPLS L2VPN ·········································································323
Overview························································································································································323
Basic concepts of MPLS L2VPN············································································································323
Remote connection model ·····················································································································324
Remote connection establishment·········································································································324
PW types················································································································································325
Control word···········································································································································327
PW redundancy······································································································································327
Multi-segment PW··································································································································328
VCCV·····················································································································································329
Restrictions and guidelines for MPLS L2VPN································································································330
MPLS L2VPN configuration task list··············································································································330
Enabling L2VPN·············································································································································331
Configuring an Ethernet service instance on an interface ·············································································331
Configuring a cross-connect ··························································································································331
Configuring a PW···········································································································································332
Configuring a PW class··························································································································332
Configuring a static PW··························································································································332
Configuring an LDP PW·························································································································333
Configuring a BGP PW ··························································································································333
Configuring a remote CCC connection ··································································································335
Binding an Ethernet service instance to a cross-connect··············································································336
Configuring PW redundancy··························································································································337
Configuring static PW redundancy·········································································································337
Configuring LDP PW redundancy··········································································································338
Enabling SNMP notifications for L2VPN PW ·································································································338
Displaying and maintaining MPLS L2VPN·····································································································338
MPLS L2VPN configuration examples···········································································································339

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Configuring a static PW··························································································································339
Configuring an LDP PW·························································································································343
Configuring a BGP PW ··························································································································347
Configuring a remote CCC connection ··································································································352
Configuring LDP PW redundancy··········································································································355
Configuring an intra-domain multi-segment PW ····················································································361
Configuring an inter-domain multi-segment PW ····················································································364
Configuring VPLS······················································································371
Overview························································································································································371
Basic VPLS architecture ························································································································371
VPLS implementation·····························································································································372
H-VPLS··················································································································································374
Restrictions and guidelines for VPLS·············································································································376
VPLS configuration task list ···························································································································376
Enabling L2VPN·············································································································································377
Configuring an Ethernet service instance ······································································································377
Configuring a VSI···········································································································································378
Configuring a PW···········································································································································378
Configuring a PW class··························································································································378
Configuring a static PW··························································································································378
Configuring an LDP PW·························································································································379
Configuring a BGP PW ··························································································································379
Configuring a BGP auto-discovery LDP PW··························································································381
Binding an Ethernet service instance to a VSI·······························································································383
Configuring UPE dual homing························································································································384
Configuring static PW redundancy·········································································································384
Configuring LDP PW redundancy··········································································································385
Configuring MAC address learning················································································································386
Enabling SNMP notifications for L2VPN PW ·································································································386
Displaying and maintaining VPLS··················································································································386
VPLS configuration examples························································································································387
Static PW configuration example···········································································································387
LDP PW configuration example·············································································································392
BGP PW configuration example·············································································································394
BGP auto-discovery LDP PW configuration example············································································399
H-VPLS using MPLS access configuration example ·············································································403
Ethernet service instance and VSI binding configuration example························································408
H-VPLS UPE dual homing configuration example·················································································412
Configuring MPLS OAM ············································································418
Overview························································································································································418
MPLS ping··············································································································································418
MPLS tracert··········································································································································418
Protocols and standards ································································································································418
Restrictions and guidelines for MPLS OAM···································································································418
Configuring MPLS OAM for LSP tunnels·······································································································418
Configuring MPLS ping for LSPs ···········································································································419
Configuring MPLS tracert for LSPs········································································································419
Configuring MPLS OAM for MPLS TE tunnels·······························································································419
Configuring MPLS ping for MPLS TE tunnels························································································419
Configuring MPLS tracert for MPLS TE tunnels·····················································································419
Configuring MPLS OAM for a PW··················································································································419
Configuring MCE ·······················································································421
MPLS L3VPN overview··································································································································421
Basic MPLS L3VPN architecture ···········································································································421
MPLS L3VPN concepts··························································································································421
MCE overview················································································································································423
MCE configuration task list·····························································································································424
Configuring VPN instances····························································································································424
Creating a VPN instance························································································································425

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Associating a VPN instance with an interface························································································425
Configuring route related attributes for a VPN instance·········································································425
Configuring routing on an MCE······················································································································426
Configuring routing between an MCE and a VPN site···········································································427
Configuring routing between an MCE and a PE ····················································································431
Displaying and maintaining MCE···················································································································434
MCE configuration examples·························································································································434
Configuring the MCE that uses OSPF to advertise VPN routes to the PE·············································434
Configuring the MCE that uses EBGP to advertise VPN routes to the PE ············································439
Configuring IPv6 MCE···············································································444
IPv6 MPLS L3VPN overview··························································································································444
IPv6 MCE overview········································································································································444
IPv6 MCE configuration task list ····················································································································444
Configuring VPN instances····························································································································445
Creating a VPN instance························································································································445
Associating a VPN instance with an interface························································································445
Configuring route related attributes for a VPN instance·········································································446
Configuring routing on an MCE······················································································································447
Configuring routing between an MCE and a VPN site···········································································447
Configuring routing between an MCE and a PE ····················································································452
Displaying and maintaining IPv6 MCE···········································································································454
IPv6 MCE configuration example···················································································································455
Network requirements····························································································································455
Configuration procedure·························································································································455
Verifying the configuration······················································································································459
Document conventions and icons······························································461
Conventions···················································································································································461
Network topology icons··································································································································462
Support and other resources ·····································································463
Accessing Hewlett Packard Enterprise Support·····························································································463
Accessing updates·········································································································································463
Websites ················································································································································464
Customer self repair·······························································································································464
Remote support······································································································································464
Documentation feedback ·······················································································································464
Index··········································································································466

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, 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 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).
TC
0
S
19 2223 31
Label TTL
Layer 2 header Layer 3 header
Label Layer 3 data

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 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. 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.
LSR A
LSR B LSR C
LSR D
LSP
LSP
LSP

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.
Ingress LSR LSP Egress LSR
Transit LSR
IP network IP network
MPLS network

4
Figure 4 Dynamic LSP establishment
MPLS forwarding
As shown in Figure 5, a packet is forwarded over the MPLS network as follows:
1. Device 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 1/0/2 to the next hop LSR
Device C.
2. When receiving the labeled packet, Device 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 1/0/2 to the next
hop LSR Device D.
3. When receiving the labeled packet, Device D (the egress 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 1/0/2 to the next hop LSR
Device E.
If the LFIB entry records no outgoing interface or next hop information, Device D performs the
following operations:
d. Identifies the FIB entry by the IP header.
e. Forwards the packet according to the FIB entry.
LSR A LSR B LSR D
LSR C
LSR E LSR F LSR G
LSR H
Ingress Egress
LSP
Label mapping

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
Restrictions and guidelines for basic MPLS
When you configure MPLS, follow these restrictions and guidelines:
•
The LSUM1TGS48SG0 (JH197A, JH205A) interface modules do not support PHP in the
current software version.
Device A Device B
Ingress Device C Device D
Egress Device E
Device 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
GE1/0/1 GE1/0/2
GE1/0/1
GE1/0/2
GE1/0/1
GE1/0/2
FIB table
LFIB table
LFIB table
Nexthop
Dest Out int
Out label
10.1.0.0GE1/0/2
40 Device C
Nexthop
Device D Out int
GE1/0/2
Out label
50
Oper
Swap
In label
40
Nexthop
Device E Out int
GE1/0/2
Out label
--
Oper
Pop
In label
50

6
•
The following interface modules support PHP only when the operating mode is bridging or
normal:
EA interface modules:
−LSU1GP24TXEA0 (JC621A, JG380A).
−LSU1GP48EA0 (JC622A, JG381A).
−LSU1GT48EA0 (JC623A, JG382A).
−LSU1TGX4EA0 (JC624A, JG383A).
EB interface modules:
−LSU1GP48EB0 (JC625A, JG384A).
−LSU1GP24TXEB0 (JC626A, JG337A).
−LSU1TGX4EB0 (JC627A, JG386A).
SE interface modules:
−LSU1GP24TXSE0 (JC617A, JG376A).
−LSU1GT48SE0 (JC618A, JG377A).
−LSU1GP48SE0 (JC619A, JG378A).
−LSU1TGX4SE0 (JC620A, JG379A).
−LSU1GP24TSE0 (JC763A, JG347A).
For more information about the operating modes, see Fundamentals Configuration Guide.
•
If the switch acts as an egress, it can de-encapsulate MPLS packets with a maximum of two
labels.
•
SC interface modules do not support MPLS:
•
Basic MPLS is mutually exclusive with EVI and VXLAN. For more information about EVI and
VXLAN, see EVI Configuration Guide and VXLAN Configuration Guide.
MPLS configuration task list
Tasks at a glance
(Required.) Enabling MPLS
(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 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:

7
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 viewof 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.
You cannot enable MPLS on the
egress interface of an IP tunnel
source because an LSP cannot
forward packets encapsulated
by an IP tunnel.
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 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 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 directly forwards the packet.
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.

8
•
If you do not configure the MPLS MTU of an interface, fragmentation for MPLS packets is based
on the IP MTU. If IP MTU is not configured, fragmentation for MPLS packets is based on the
MTU of the interface. The length of a fragment does not include that of the MPLS label. Thus,
after an MPLS label is added into a fragment, the length of the MPLS fragment might exceed
the interface MTU.
Specifying the label type advertised by egress
In an MPLS network, an egress node 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.
For LSPs established by a label distribution protocol, the label advertised by the egress node
determines how the penultimate hop processes a labeled packet.
•
If the egress node advertises an implicit null label, the penultimate hop directly pops the top
label of a matching packet.
•
If the egress node 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 node advertises a non-null label, the penultimate hop swaps the top label of a
matching packet with the label assigned by the egress node.
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 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 node, the egress node 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 node.
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.
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
node to the penultimate hop.
mpls label advertise
{ explicit-null | implicit-null |
non-null }
By default, an egress node
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

9
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 TTL propagation is disabled, the ingress node sets the label TTL to 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:
•
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.
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

10
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 TTL of 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 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 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 SNMP on 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:
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.
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 for 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 [ p2mp ] | static |
static-cr } | transit ] [ vpn-instance vpn-instance-name ]
[ ipv4-address mask-length | ipv6 [ ipv6-address
prefix-length ] ] [ verbose ]
Displ
ay MPLS Nexthop Information Base (NIB)
information. display mpls nib [ nib-id ]
Display usage information for NIDs. display mpls nid [ nid-value1 [ to nid-value2 ] ]
Display LSP statistics. display mpls lsp statistics [ ipv6 ]
Display MPLS summary information.
display mpls summary

11
Task
Command
(In standalone mode.) Display ILM entries. display mpls forwarding ilm [ label ] [ slot slot-number ]
(In IRF mode.) Display ILM entries. display mpls forwarding ilm [ label ] [ chassis
chassis-number slot slot-number ]
(In standalone mode.) Display NHLFE entries. display mpls forwarding nhlfe [ nid ] [ slot slot-number ]
(In IRF mode.) Display NHLFE entries. display mpls forwarding nhlfe [ nid ] [ chassis
chassis-number slot slot-number ]
Clear MPLS forwarding statistics for the
specified LSPs.
reset 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 }