HP MSR2000 Series User manual

HP MSR Router Series
MPLS
Configuration Guide(V7)
Part number: 5998-5680
Software version: CMW710-R0106
Document version: 6PW100-20140607

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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 the egress·······································································································7
Configuring TTL propagation···········································································································································7
Enabling sending of MPLS TTL-expired messages ·········································································································9
Enabling MPLS forwarding statistics ·······························································································································9
Enabling FTN forwarding statistics·························································································································9
Enabling MPLS label forwarding statistics ·········································································································· 10
Enabling SNMP notifications for MPLS························································································································ 10
Displaying and maintaining MPLS ······························································································································· 10
Configuring a static LSP·············································································································································12
Overview········································································································································································· 12
Configuration prerequisites··········································································································································· 12
Configuration procedure··············································································································································· 12
Displaying static LSPs····················································································································································· 13
Static LSP configuration example ································································································································· 13
Configuring LDP ·························································································································································16
Overview········································································································································································· 16
Terminology ··························································································································································· 16
LDP messages························································································································································· 16
LDP operation························································································································································· 17
Label distribution and control······························································································································· 18
LDP GR···································································································································································· 20
LDP NSR ································································································································································· 21
LDP-IGP synchronization ······································································································································· 22
LDP FRR··································································································································································· 23
Protocols ································································································································································· 23
LDP configuration task list·············································································································································· 23
Enabling LDP··································································································································································· 24
Enabling LDP globally··········································································································································· 24
Enabling LDP on an interface······························································································································· 25
Configuring Hello parameters ······································································································································ 25
Configuring LDP session parameters···························································································································· 26
Configuring LDP backoff ··············································································································································· 27
Configuring LDP MD5 authentication ·························································································································· 27
Configuring LDP to redistribute BGP IPv4 unicast routes ··························································································· 28
Configuring an LSP generation policy ························································································································· 28
Configuring the LDP label distribution control mode·································································································· 29
Configuring a label advertisement policy ··················································································································· 29

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Configuring a label acceptance policy ······················································································································· 30
Configuring LDP loop detection···································································································································· 31
Configuring LDP session protection······························································································································ 32
Configuring LDP GR······················································································································································· 33
Configuring LDP NSR····················································································································································· 33
Configuring LDP-IGP synchronization ·························································································································· 33
Configuring LDP-OSPF synchronization ·············································································································· 33
Configuring LDP-ISIS synchronization ················································································································· 35
Configuring LDP FRR ······················································································································································ 35
Specifying a DSCP value for outgoing LDP packets··································································································· 36
Resetting LDP sessions···················································································································································· 36
Enabling SNMP notifications for LDP··························································································································· 36
Displaying and maintaining LDP ·································································································································· 36
LDP configuration examples·········································································································································· 37
LDP LSP configuration example···························································································································· 37
Label acceptance control configuration example ······························································································ 41
Label advertisement control configuration example ·························································································· 45
LDP FRR configuration example ··························································································································· 51
Configuring MPLS TE ·················································································································································54
Overview········································································································································································· 54
TE and MPLS TE····················································································································································· 54
MPLS TE basic concepts········································································································································ 54
Static CRLSP establishment ··································································································································· 54
Dynamic CRLSP establishment ····························································································································· 54
Traffic forwarding·················································································································································· 56
Make-before-break ················································································································································ 57
Route pinning························································································································································· 58
Tunnel reoptimization············································································································································ 58
Automatic bandwidth adjustment ························································································································ 59
CRLSP backup························································································································································ 59
FRR ·········································································································································································· 59
DiffServ-aware TE ·················································································································································· 60
Bidirectional MPLS TE tunnel ································································································································ 62
Protocols and standards ······································································································································· 63
MPLS TE configuration task list ····································································································································· 63
Enabling MPLS TE ·························································································································································· 64
Configuring a tunnel interface······································································································································ 65
Configuring DS-TE·························································································································································· 65
Configuring an MPLS TE tunnel to use a static CRLSP································································································ 66
Configuring an MPLS TE tunnel to use a dynamic CRLSP·························································································· 66
Configuration task list ··········································································································································· 67
Configuring MPLS TE attributes for a link ··········································································································· 67
Advertising link TE attributes by using IGP TE extension··················································································· 68
Configuring MPLS TE tunnel constraints·············································································································· 69
Establishing an MPLS TE tunnel by using RSVP-TE ····························································································· 71
Controlling CRLSP path selection························································································································· 71
Controlling MPLS TE tunnel setup ························································································································ 74
Configuring load sharing for an MPLS TE tunnel········································································································ 76
Configuring traffic forwarding······································································································································ 77
Configuring static routing to direct traffic to an MPLS TE tunnel or tunnel bundle ········································· 77
Configuring PBR to direct traffic to an MPLS TE tunnel or tunnel bundle························································· 78
Configuring automatic route advertisement to direct traffic to an MPLS TE tunnel or tunnel bundle············ 78
Configuring a bidirectional MPLS TE tunnel················································································································ 80
Configuring CRLSP backup ··········································································································································· 81

iii
Configuring MPLS TE FRR·············································································································································· 81
Enabling FRR·························································································································································· 81
Configuring a bypass tunnel on the PLR ············································································································· 82
Configuring node fault detection························································································································· 85
Configuring the optimal bypass tunnel selection interval·················································································· 86
Enabling SNMP notifications for MPLS TE··················································································································· 86
Displaying and maintaining MPLS TE ·························································································································· 87
MPLS TE configuration examples·································································································································· 87
Establishing an MPLS TE tunnel over a static CRLSP·························································································· 87
Establishing an MPLS TE tunnel with RSVP-TE ···································································································· 92
Establishing an inter-AS MPLS TE tunnel with RSVP-TE ······················································································ 98
Bidirectional MPLS TE tunnel configuration example·······················································································105
CRLSP backup configuration example ··············································································································111
Manual bypass tunnel for FRR configuration example····················································································115
Auto FRR configuration example ·······················································································································121
IETF DS-TE configuration example ·····················································································································127
Troubleshooting MPLS TE ············································································································································134
No TE LSA generated ·········································································································································134
Configuring a static CRLSP····································································································································· 136
Overview·······································································································································································136
Configuration procedure·············································································································································136
Displaying static CRLSPs··············································································································································137
Static CRLSP configuration example ··························································································································137
Configuring RSVP···················································································································································· 143
Overview·······································································································································································143
RSVP messages····················································································································································143
CRLSP setup procedure ·······································································································································144
RSVP refresh mechanism·····································································································································144
RSVP authentication ············································································································································145
RSVP GR·······························································································································································145
Protocols and standards ·····································································································································146
RSVP configuration task list·········································································································································146
Enabling RSVP······························································································································································146
Configuring RSVP refresh ············································································································································147
Configuring RSVP Srefresh and reliable RSVP message delivery ···········································································147
Configuring RSVP hello extension ······························································································································147
Configuring RSVP authentication································································································································148
Specifying a DSCP value for outgoing RSVP packets ······························································································150
Configuring RSVP GR ··················································································································································150
Enabling BFD for RSVP ················································································································································151
Displaying and maintaining RSVP······························································································································151
RSVP configuration examples ·····································································································································152
Establishing an MPLS TE tunnel with RSVP-TE ··································································································152
RSVP GR configuration example ·······················································································································157
Configuring tunnel policies····································································································································· 160
Overview·······································································································································································160
Configuring a tunnel policy ········································································································································160
Configuration guidelines ····································································································································160
Configuration procedure ····································································································································161
Displaying tunnel information ·····································································································································162
Tunnel policy configuration examples ·······················································································································162
Preferred tunnel configuration example ············································································································162
Exclusive tunnel configuration example ············································································································162

iv
Tunnel selection order configuration example ·································································································163
Preferred tunnel and tunnel selection order configuration example ······························································164
Configuring MPLS L3VPN······································································································································· 166
Overview·······································································································································································166
Basic MPLS L3VPN architecture·························································································································166
MPLS L3VPN concepts ········································································································································167
MPLS L3VPN route advertisement······················································································································168
MPLS L3VPN packet forwarding························································································································169
MPLS L3VPN networking schemes·····················································································································170
Inter-AS VPN ························································································································································172
Carrier's carrier ···················································································································································176
Nested VPN ·························································································································································178
HoVPN··································································································································································179
OSPF VPN extension···········································································································································181
BGP AS number substitution and SoO attribute·······························································································183
MPLS L3VPN FRR·················································································································································184
Multi-VPN instance CE ········································································································································186
Protocols and standards ·····································································································································187
MPLS L3VPN configuration task list····························································································································188
Configuring basic MPLS L3VPN ·································································································································188
Configuration prerequisites ································································································································188
Configuring VPN instances ································································································································188
Configuring routing between a PE and a CE···································································································190
Configuring routing between PEs ······················································································································196
Configuring BGP VPNv4 route control ·············································································································196
Configuring inter-AS VPN ···········································································································································198
Configuring inter-AS option A····························································································································198
Configuring inter-AS option B ····························································································································199
Configuring inter-AS option C····························································································································200
Configuring nested VPN··············································································································································203
Configuring HoVPN·····················································································································································204
Configuring an OSPF sham link ·································································································································205
Configuring a loopback interface ·····················································································································205
Redistributing the loopback interface route ······································································································206
Creating a sham link···········································································································································206
Configuring routing on an MCE·································································································································206
Configuring routing between an MCE and a VPN site···················································································207
Configuring routing between an MCE and a PE ·····························································································212
Specifying the VPN label processing mode on the egress PE·················································································215
Configuring BGP AS number substitution and SoO attribute··················································································216
Enabling SNMP notifications for MPLS L3VPN·········································································································216
Configuring MPLS L3VPN FRR····································································································································217
Displaying and maintaining MPLS L3VPN ················································································································219
MPLS L3VPN configuration examples························································································································221
Configuring basic MPLS L3VPN ························································································································221
Configuring MPLS L3VPN over a GRE tunnel···································································································228
Configuring a hub-spoke network ·····················································································································233
Configuring MPLS L3VPN inter-AS option A ····································································································239
Configuring MPLS L3VPN inter-AS option B·····································································································244
Configuring MPLS L3VPN inter-AS option C ····································································································249
Configuring MPLS L3VPN carrier's carrier ·······································································································256
Configuring nested VPN·····································································································································263
Configuring HoVPN ············································································································································273
Configuring an OSPF sham link ························································································································280

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Configuring MCE ················································································································································284
Configuring BGP AS number substitution ·········································································································290
Configuring BGP AS number substitution and SoO attribute ·········································································293
Configuring MPLS L3VPN FRR through VPNv4 route backup for a VPNv4 route········································296
Configuring MPLS L3VPN FRR through VPNv4 route backup for an IPv4 route···········································298
Configuring MPLS L3VPN FRR through IPv4 route backup for a VPNv4 route·············································300
Configuring IPv6 MPLS L3VPN ······························································································································ 303
Overview·······································································································································································303
IPv6 MPLS L3VPN packet forwarding ···············································································································304
IPv6 MPLS L3VPN routing information advertisement ·····················································································304
IPv6 MPLS L3VPN network schemes and functions··························································································305
Protocols and standards ·····································································································································305
IPv6 MPLS L3VPN configuration task list ···················································································································305
Configuring basic IPv6 MPLS L3VPN·························································································································305
Configuring VPN instances ································································································································306
Configuring routing between a PE and a CE···································································································308
Configuring routing between PEs ······················································································································313
Configuring BGP VPNv6 route control ·············································································································313
Configuring inter-AS IPv6 VPN···································································································································314
Configuring inter-AS IPv6 VPN option A ··········································································································315
Configuring inter-AS IPv6 VPN option C ··········································································································315
Configuring routing on an MCE·································································································································316
Configuring routing between an MCE and a VPN site···················································································316
Configuring routing between an MCE and a PE ·····························································································321
Configuring BGP AS number substitution and SoO attribute··················································································325
Displaying and maintaining IPv6 MPLS L3VPN········································································································325
IPv6 MPLS L3VPN configuration examples ···············································································································327
Configuring IPv6 MPLS L3VPNs·························································································································327
Configuring an IPv6 MPLS L3VPN over a GRE tunnel ····················································································334
Configuring IPv6 MPLS L3VPN inter-AS option A····························································································338
Configuring IPv6 MPLS L3VPN inter-AS option C····························································································343
Configuring IPv6 MPLS L3VPN carrier's carrier·······························································································350
Configuring IPv6 MCE········································································································································358
Configuring BGP AS number substitution ·········································································································363
Configuring BGP AS number substitution and SoO attribute ·········································································368
Configuring MPLS L2VPN······································································································································· 371
Overview·······································································································································································371
Basic concepts of MPLS L2VPN ·························································································································371
MPLS L2VPN network models ····························································································································372
Remote connection establishment ······················································································································373
Local connection establishment··························································································································374
PW types ······························································································································································374
Control word························································································································································376
MPLS L2VPN interworking··································································································································377
PW redundancy···················································································································································377
Multi-segment PW················································································································································378
VCCV····································································································································································380
MPLS L2VPN configuration task list····························································································································380
Enabling L2VPN ···························································································································································381
Configuring an AC ······················································································································································381
Configuring the interface with Ethernet or VLAN encapsulation····································································381
Configuring the interface with PPP encapsulation ···························································································382
Configuring the interface with HDLC encapsulation························································································382

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Configuring a cross-connect ·······································································································································382
Configuring a PW························································································································································383
Configuring a PW class······································································································································383
Configuring a static PW ·····································································································································383
Configuring an LDP PW······································································································································384
Configuring a BGP PW ······································································································································384
Configuring a remote CCC connection ············································································································386
Binding an AC to a cross-connect······························································································································387
Configuring PW redundancy······································································································································388
Configuring static PW redundancy ···················································································································388
Configuring LDP PW redundancy······················································································································388
Configuring interworking for a cross-connect ···········································································································389
Displaying and maintaining MPLS L2VPN ················································································································390
MPLS L2VPN configuration examples························································································································391
Configuring local MPLS L2VPN connections ····································································································391
Configuring IP interworking over local MPLS L2VPN connections·································································392
Configuring a static PW ·····································································································································393
Configuring an LDP PW······································································································································397
Configuring IP interworking over an LDP PW ··································································································401
Configuring a BGP PW ······································································································································405
Configuring a remote CCC connection ············································································································408
Configuring an intra-domain multi-segment PW ······························································································412
Configuring an inter-domain multi-segment PW ······························································································415
Configuring MPLS OAM········································································································································· 422
Overview·······································································································································································422
MPLS ping ····························································································································································422
MPLS traceroute···················································································································································422
Periodic MPLS traceroute····································································································································422
MPLS BFD ·····························································································································································423
Protocols and standards ··············································································································································423
Configuring MPLS OAM for LSP tunnels····················································································································423
Configuring MPLS ping for LSPs ························································································································424
Configuring MPLS traceroute for LSPs···············································································································424
Configuring periodic MPLS traceroute for LSPs································································································424
Configuring MPLS BFD for LSPs ·························································································································424
Configuring MPLS OAM for MPLS TE tunnels ···········································································································425
Configuring MPLS ping for MPLS TE tunnels ····································································································425
Configuring MPLS traceroute for MPLS TE tunnels···························································································425
Configuring MPLS BFD for MPLS TE tunnels ·····································································································426
Configuring MPLS OAM for a PW·····························································································································426
Configuring MPLS ping for a PW······················································································································427
Configuring BFD for a PW ·································································································································427
Displaying MPLS OAM················································································································································429
BFD for LSP configuration example····························································································································429
Configuring MPLS protection switching················································································································· 432
Overview·······································································································································································432
Protection switching triggering modes ··············································································································432
Protection switching modes ································································································································433
Path switching modes··········································································································································433
Protocols and standards ··············································································································································433
MPLS protection switching configuration task list ·····································································································434
Enabling MPLS protection switching ··························································································································434
Creating a protection group ·······································································································································435

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Configuring PS attributes for the protection group···································································································436
Configuring command switching for the protection group······················································································437
Configuring the PSC message sending interval········································································································437
Displaying and maintaining MPLS protection switching··························································································437
MPLS protection switching configuration example···································································································438
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1
Configuring basic MPLS
In this chapter, "MSR2000" refers to MSR2003. "MSR3000" collectively refers to MSR3012, MSR3024,
MSR3044, MSR3064. "MSR4000" collectively refers to MSR4060 and MSR4080.
Overview
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.
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 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 routing loop prevention.

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:

3
•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.
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.
Figure 4 Dynamic LSP establishment

4
MPLS forwarding
Figure 5 MPLS forwarding
As shown in Figure 5, a packet is forwarded over the MPLS network as follows:
1. Router B (the ingress LSR) receives a packet with no label. It then does the following:
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 2/1/2 to the next hop LSR
Router C.
2. When receiving the labeled packet, Router C processes the packet as follows:
a. Identifies the LFIB entry that has an incoming label of 40.
b. Uses the outgoing label 50 of the entry to replace label 40 in the packet.
c. Forwards the labeled packet out of the outgoing interface GigabitEthernet 2/1/2 to the next
hop 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 GigabitEthernet 2/1/2 to the next hop LSR
Router E.
If the LFIB entry records no outgoing interface or next hop information, Router D does the following:
d. Identifies the FIB entry by the IP header.
e. 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).

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
g
lance
(Required.) Enabling MPLS
(Optional.) Configuring MPLS MTU
(Optional.) Specifying the label type advertised by the 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
You must enable MPLS on all interfaces related to MPLS forwarding.
Before you enable MPLS, complete 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:
Ste
p
Command Remarks
1. Enter system view. system-view N/A

6
Ste
p
Command Remarks
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. HP
recommends that you use the IP
address of a loopback interface as
an LSR ID.
3. Enter the view of the interface that
needs to perform MPLS
forwarding.
interface interface-type
interface-number N/A
4. Enable MPLS on the interface. mpls enable By default, MPLS is disabled on the
interface.
Configuring 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 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:
Ste
p
Command Remarks
5. Enter system view. system-view N/A
6. Enter interface view. interface interface-type
interface-number N/A
7. 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.

7
Specifying the label type advertised by the egress
In an MPLS network, an egress can advertise the following types of labels:
•Implicit null label with a value of 3.
•Explicit null label with a value of 0.
•Non-null label.
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
If the penultimate hop supports PHP, HP recommends that you configure the egress to advertise an
implicit null label to the penultimate hop. If you want to simplify packet forwarding on the egress but keep
labels to determine QoS policies, configure the egress to advertise an explicit null label to the
penultimate hop. HP recommends using 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 reestablishes 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:
Ste
p
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 TTL value back to the IP TTL of the packet, so the IP TTL value can reflect how many

8
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:
•HP recommends setting 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:
Ste
p
Command Remarks
1. Enter system view. system-view N/A

9
Ste
p
Command Remarks
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.
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 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, which then sends the message back to the source.
To enable sending of MPLS TTL-expired messages:
Ste
p
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
Enabling FTN forwarding statistics
FEC-to-NHLFE map (FTN) entries are FIB entries that contain outgoing labels used for FTN forwarding.
When an LSR receives an unlabeled packet, it searches for the corresponding FTN entry based on the
destination IP address. If a match is found, the LSR adds the outgoing label in the FTN entry to the packet
and forwards the labeled packet.
To enable FTN forwarding statistics:
Ste
p
Command Remarks
1. Enter system view. system-view N/A
2. Enter RIB view. rib N/A
3. Create a RIB IPv4 address
family and enter RIB IPv4
address family view.
address-family ipv4 By default, no RIB IPv4 address
family is created.
4. Enable the device to maintain
FTN entries in the RIB. ftn enable By default, the device does not
maintain FTN entries in the RIB.
5. Enable FTN forwarding
statistics for a destination
network.
mpls-forwarding statistics prefix-list
prefix-list-name
By default, FTN forwarding
statistics is disabled for all
destination networks.

10
Enabling MPLS label forwarding statistics
MPLS label forwarding forwards a labeled packet based on its incoming label.
Perform this task to enable MPLS label forwarding statistics and MPLS statistics reading, so that you can
use the display mpls lsp verbose command to view MPLS label statistics.
To enable MPLS label forwarding statistics:
Ste
p
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 are disabled
for all LSPs.
3. Enable MPLS label statistics
reading, and specify the
reading interval.
mpls statistics interval interval By default, MPLS label statistics
reading is disabled.
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:
Ste
p
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 | static | static-cr } | transit ] [ vpn-instance
vpn-instance-name ] [ ipv4-dest mask-length | ipv6 [ ipv6-dest
prefix-length ] ] [ verbose ]

11
Task Command
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
(MSR2000/MSR3000). display mpls forwarding ilm [ label ]
Display ILM entries (MSR4000). display mpls forwarding ilm [ label ] [ slot slot-number ]
Display NHLFE entries
(MSR2000/MSR3000). display mpls forwarding nhlfe [ nid ]
Display NHLFE entries (MSR4000). 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 }