HP 12500 Series User manual

HP 12500 Routing Switch Series
MPLS
Configuration Guide
Part number: 5998-2826
Software version: A12500-CMW520-R1726
Document version: 6W170-20111130

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i
Contents
Configuring basic MPLS ·············································································································································· 1
MPLS overview ··································································································································································1
Basic concepts ··························································································································································1
MPLS network structure ············································································································································3
LSP establishment and label distribution ················································································································3
MPLS forwarding ······················································································································································6
LDP ·············································································································································································8
Protocols ····································································································································································9
MPLS configuration task list··············································································································································9
Enabling the MPLS function··········································································································································· 10
Configuration prerequisites ·································································································································· 10
Configuration procedure ······································································································································ 11
Configuring a static LSP ················································································································································ 11
Configuration prerequisites ·································································································································· 11
Configuration procedure ······································································································································ 11
Establishing dynamic LSPs through LDP······················································································································· 12
Configuring MPLS LDP capability ························································································································ 12
Configuring local LDP session parameters ········································································································· 13
Configuring remote LDP session parameters ······································································································ 13
Configuring PHP ···················································································································································· 14
Configuring the policy for triggering LSP establishment ··················································································· 15
Configuring the label distribution control mode ································································································ 16
Configuring LDP loop detection ··························································································································· 16
Configuring LDP MD5 authentication·················································································································· 17
Configuring LDP label filtering ····························································································································· 17
Maintaining LDP sessions ·············································································································································· 19
Configuring BFD for MPLS LDP ···························································································································· 19
Resetting LDP sessions··········································································································································· 20
Managing and optimizing MPLS forwarding ············································································································· 20
Configuring MPLS MTU ········································································································································ 20
Configuring TTL processing mode at ingress······································································································ 21
Sending back ICMP TTL exceeded messages for MPLS TTL expired packets ················································· 22
Configuring LDP GR ·············································································································································· 23
Configuring MPLS statistics collection and reading ··································································································· 25
Setting MPLS statistics reading interval ··············································································································· 25
Inspecting LSPs ······························································································································································· 26
Configuring MPLS LSP ping·································································································································· 26
Configuring MPLS LSP tracert······························································································································· 26
Configuring BFD for LSPs······································································································································ 26
Configuring periodic LSP tracert·························································································································· 28
Enabling MPLS trap························································································································································ 28
Displaying and maintaining MPLS ······························································································································· 29
Displaying MPLS operation ·································································································································· 29
Displaying MPLS LDP operation··························································································································· 30
Clearing MPLS statistics ········································································································································ 31
MPLS configuration examples······································································································································· 31
Configuring static LSPs·········································································································································· 32
Configuring LDP to establish LSPs dynamically·································································································· 34
Configuring BFD for LSPs······································································································································ 38

ii
Configuring MPLS TE ·················································································································································41
MPLS TE overview ·························································································································································· 41
Traffic engineering and MPLS TE························································································································· 41
Basic concepts ······················································································································································· 42
MPLS TE implementation······································································································································· 42
CR-LSP····································································································································································· 43
RSVP-TE··································································································································································· 44
Traffic forwarding·················································································································································· 48
CR-LSP backup ······················································································································································· 49
FRR ·········································································································································································· 49
PS for an MPLS TE tunnel······································································································································ 51
Protocols and standards ······································································································································· 51
MPLS TE configuration task list ····································································································································· 52
Configuring MPLS TE basic settings ····························································································································· 52
Configuration prerequisites ·································································································································· 52
Configuration procedure ······································································································································ 52
Creating MPLS TE tunnel over static CR-LSP ················································································································ 53
Configuration prerequisites ·································································································································· 53
Configuration procedure ······································································································································ 54
Configuring MPLS TE tunnel with dynamic signaling protocol·················································································· 54
Configuration prerequisites ·································································································································· 55
Configuration procedure ······································································································································ 55
Configuring RSVP-TE advanced features ····················································································································· 59
Configuration prerequisites ·································································································································· 59
Configuration procedure ······································································································································ 59
Tuning CR-LSP setup······················································································································································· 63
Configuration prerequisites ·································································································································· 63
Configuration procedure ······································································································································ 63
Tuning MPLS TE tunnel setup········································································································································· 65
Configuration prerequisites ·································································································································· 66
Configuration procedures····································································································································· 66
Configuring traffic forwarding······································································································································ 67
Configuration prerequisites ·································································································································· 67
Configuration procedures····································································································································· 67
Configuring traffic forwarding tuning parameters······································································································ 69
Configuration prerequisites ·································································································································· 69
Configuration procedure ······································································································································ 69
Configuring CR-LSP backup ·········································································································································· 71
Configuration prerequisites ·································································································································· 71
Configuration procedure ······································································································································ 71
Configuring FRR ····························································································································································· 72
Configuration prerequisites ·································································································································· 72
Configuration procedure ······································································································································ 72
Inspecting an MPLS TE tunnel ······································································································································· 74
Configuring MPLS LSP ping·································································································································· 75
Configuring MPLS LSP tracert······························································································································· 75
Configuring BFD for an MPLS TE tunnel·············································································································· 75
Configuring periodic LSP tracert·························································································································· 77
Configuring protection switching ································································································································· 77
Configuration prerequisites ·································································································································· 77
Configuration procedure ······································································································································ 78
Displaying and maintaining MPLS TE ················································································································· 78
MPLS TE configuration examples·································································································································· 81
MPLS TE using static CR-LSP configuration example·························································································· 81

iii
MPLS TE using RSVP-TE configuration example ································································································· 86
Configuration example of inter-AS MPLS TE tunnel using RSVP-TE·································································· 92
RSVP-TE GR configuration example····················································································································· 98
MPLS RSVP-TE and BFD cooperation configuration example·········································································101
CR-LSP backup configuration example ·············································································································103
FRR configuration example·································································································································106
MPLS TE in MPLS L3VPN configuration example·····························································································115
Troubleshooting MPLS TE ············································································································································123
No TE LSA generated ·········································································································································123
Swicthback fails to occur when the main tunnel resumes ···············································································123
Configuring VPLS ···················································································································································· 124
VPLS overview ······························································································································································124
Operation of VPLS···············································································································································124
VPLS packet encapsulation·································································································································127
H-VPLS implementation ·······································································································································128
Hub-spoke VPLS implementation························································································································130
Multi-hop PW·······················································································································································131
VPLS configuration task list··········································································································································132
Enabling L2VPN and MPLS L2VPN····························································································································132
Configuring LDP VPLS ··················································································································································132
Configuration prerequisites ································································································································132
Configuring an LDP VPLS instance·····················································································································133
Configuring BGP VPLS·················································································································································134
Configuration prerequisites ································································································································134
Configuring the BGP extension··························································································································134
Configuring a BGP VPLS instance ·····················································································································135
Resetting VPLS BGP connections························································································································135
Binding a VPLS instance··············································································································································135
Binding a Layer 3 interface with a VPLS instance ···························································································136
Binding a service instance with a VPLS instance ·····························································································136
Configuring VPLS and MAC-in-MAC dual-stack support ·························································································137
Configuring MAC address learning···························································································································138
Configuring VPLS instance attributes··························································································································139
Configuring traffic policing for an AC·······················································································································139
Inspecting PWs·····························································································································································140
Displaying and maintaining VPLS ······························································································································141
VPLS configuration examples······································································································································142
Configuring VPLS instances································································································································142
Configuring H-VPLS with LSP access ·················································································································146
Configuring hub-spoke VPLS ······························································································································149
Configuring PW redundancy for H-VPLS access······························································································153
Configuring BFD for the main link in an H-VPLS network ···············································································157
Implementing multi-AS VPN through multi-hop PW ·························································································161
VPLS and MAC-in-MAC dual-stack support configuration example ······························································167
Troubleshooting VPLS···················································································································································171
Configuring MPLS L2VPN······································································································································· 172
MPLS L2VPN overview ················································································································································172
About MPLS L2VPN·············································································································································172
Comparison with traditional VPN······················································································································173
Comparison with MPLS L3VPN··························································································································173
Basic concepts ·····················································································································································173
MPLS L2VPN implementation ·····························································································································174
MPLS L2VPN configuration task list····························································································································175

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Configuring MPLS L2VPN ···········································································································································175
Configuring a PE-CE interface of a PE·······················································································································176
Configuring Ethernet encapsulation for the interface ······················································································176
Configuring VLAN encapsulation for the interface··························································································176
Configuring Martini MPLS L2VPN ······························································································································176
Configuring a Martini MPLS L2VPN connection on a Layer 3 interface·······················································176
Configuring a Martini MPLS L2VPN connection based on Layer 2 Ethernet interface and VLAN·············177
Configuring traffic policing for an AC··············································································································180
Inspecting VCs······························································································································································180
Displaying and maintaining MPLS L2VPN ················································································································181
MPLS L2VPN configuration example ·························································································································182
Configuring a Martini MPLS L2VPN connection based on Layer 2 Ethernet interface and VLAN·············182
Configuring a Martini MPLS L2VPN on a Layer 3 Ethernet interface····························································186
Troubleshooting MPLS L2VPN·····································································································································190
Configuring MPLS L3VPN······································································································································· 191
MPLS L3VPN overview ················································································································································191
Introduction to MPLS L3VPN·······························································································································191
MPLS L3VPN concepts ········································································································································192
MPLS L3VPN packet forwarding························································································································195
MPLS L3VPN networking schemes·····················································································································195
MPLS L3VPN routing information advertisement······························································································198
Inter-AS VPN ························································································································································199
Carrier’s carrier ···················································································································································202
Nested VPN ·························································································································································204
Multi-role host·······················································································································································206
HoVPN··································································································································································206
OSPF VPN extension···········································································································································208
BGP AS number substitution and SoO··············································································································211
Multi-VPN-instance CE ········································································································································212
MPLS L3VPN configuration task list····························································································································213
Configuring basic MPLS L3VPN ·································································································································213
Configuration prerequisites ································································································································213
Configuring VPN instances ································································································································214
Configuring routing between PE and CE··········································································································218
Configuring routing between PEs ······················································································································223
Configuring routing features for BGP VPNv4 subaddress family ··································································224
Configuring inter-AS VPN ···········································································································································227
Configuration prerequisites ································································································································227
Configuring inter-AS option A····························································································································227
Configuring inter-AS option B ····························································································································228
Configuring inter-AS option C····························································································································229
Configuring nested VPN··············································································································································231
Configuration prerequisites ································································································································231
Configuring nested VPN·····································································································································231
Configuring multi-role host ··········································································································································232
Configuration prerequisites ································································································································232
Configuring and applying policy routing ·········································································································232
Configuring a static route···································································································································232
Configuring HoVPN·····················································································································································233
Configuration prerequisites ································································································································233
Configuring HoVPNs ··········································································································································233
Configuring an OSPF sham link ·································································································································234
Configuration prerequisites ································································································································234
Configuring a loopback interface ·····················································································································234

v
Redistributing the loopback interface route and OSPF routes into BGP························································234
Creating a sham link···········································································································································235
Configuring routing on an MCE·································································································································235
Configuration prerequisites ································································································································235
Configuring routing between MCE and VPN site····························································································236
Configuring routing between MCE and PE ······································································································241
Specifying the VPN label processing mode··············································································································245
Configuring BGP AS number substitution and SoO·································································································245
Configuration prerequisites ································································································································245
Configuration procedure ····································································································································245
Displaying and maintaining MPLS L3VPN ················································································································246
Resetting BGP connections ·································································································································246
Displaying and maintaining MPLS L3VPN········································································································247
MPLS L3VPN configuration examples························································································································249
Configuring MPLS L3VPNs using eBGP between PE and CE ·········································································249
Configuring MPLS L3VPNs using iBGP between PE and CE ··········································································256
Configuring a hub-spoke network ·····················································································································264
Configuring inter-AS option A····························································································································272
Configuring inter-AS option B ····························································································································277
Configuring inter-AS option C····························································································································282
Configuring carrier’s carrier in LDP mode········································································································288
Configuring carrier’s carrier in BGP mode·······································································································296
Configuring nested VPN·····································································································································304
Configuring HoVPN ············································································································································314
Configuring OSPF sham links ····························································································································321
Configuring BGP AS number substitution ·········································································································326
Configuring multi-role host··································································································································329
Configuring BGP AS number substitution and SoO ························································································334
Configuring IPv6 MPLS L3VPN ······························································································································ 337
IPv6 MPLS L3VPN overview ········································································································································337
IPv6 MPLS L3VPN packet forwarding ···············································································································338
IPv6 MPLS L3VPN routing information advertisement ·····················································································338
IPv6 MPLS L3VPN networking schemes and functions ····················································································339
IPv6 MPLS L3VPN configuration task list ···················································································································339
Configuring basic IPv6 MPLS L3VPN·························································································································339
Basic IPv6 MPLS L3VPN configuration task list ································································································339
Configuration prerequisites ································································································································340
Configuring VPN instances ································································································································340
Configuring route related attributes for a VPN instance·················································································341
Configuring routing between PE and CE··········································································································344
Configuring routing between PEs ······················································································································347
Configuring routing features for the BGP-VPNv6 subaddress family·····························································347
Configuring inter-AS IPv6 VPN···································································································································349
Configuration prerequisites ································································································································349
Configuring inter-AS IPv6 VPN option A ··········································································································349
Configuring inter-AS IPv6 VPN option C ··········································································································350
Configuring routing on an MCE·································································································································351
Configuration prerequisites ································································································································351
Configuring routing between MCE and VPN site····························································································351
Configuring routing between MCE and PE ······································································································355
Displaying and maintaining IPv6 MPLS L3VPN········································································································358
Resetting BGP connections ·································································································································358
Displaying information about IPv6 MPLS L3VPN·····························································································358
IPv6 MPLS L3VPN configuration examples ···············································································································359

vi
Configuring IPv6 MPLS L3VPNs·························································································································359
Configuring inter-AS IPv6 VPN option A ··········································································································367
Configuring inter-AS IPv6 VPN option C ··········································································································372
Configuring carrier’s carrier ······························································································································379
Configuring MCE ················································································································································386
Index ········································································································································································ 393

1
Configuring basic MPLS
NOTE:
•For more information about VPN, see the chapters “Configuring MPLS L2VPN” and “Configuring MPLS
L3VPN.”
•For more information about MPLS TE, see the chapter “Configuring MPLS TE.”
•The switch operates in IRF or standalone (the default) mode. For more information about IRF, see
IRF
Configuration Guide
.
•The term
router in this document refers to both routers and Layer 3 switches.
MPLS overview
Multiprotocol Label Switching (MPLS) enables connection-oriented label switching on connectionless IP
networks. It integrates both the flexibility of IP routing and the simplicity of Layer 2 switching.
MPLS has the following advantages:
•MPLS forwards packets according to short- and fixed-length labels, instead of Layer 3 header
analysis and complicated routing table lookup, enabling highly-efficient and fast data forwarding
on backbone networks.
•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), provide connection-oriented services
for various network layer protocols (for example, IPv4, IPv6, and IPX), and work with mainstream
network technologies.
•MPLS is connection-oriented and supports label stack. It can be used to implement various functions,
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 class, called a “forwarding equivalence class (FEC)”. Packets of the same FEC are handled
in the same way on an MPLS network. The switch supports classifying FECs according to the network
layer destination addresses.
Label
A label is a short, fixed length identifier for identifying a single FEC. A label is locally significant and
must be locally unique.

2
Figure 1 Format of a label
As shown in Figure 1, a label is encapsulated between the Layer 2 header and Layer 3 header of a
packet. A label is four bytes in length and consists of four fields:
•Label—20 bits in length. Label value for identifying a FEC.
•Exp—Three bits in length. Reserved field, usually used for CoS.
•S—One bit in length. MPLS supports multiple levels of labels. This field indicates whether a label is
at the bottom of the label stack. 1 indicates that the label is at the bottom of the label stack.
•TTL—Eight bits in length. Like the homonymous IP header field, it is used to prevent loops.
LSR
A label switching router (LSR) is a fundamental component on an MPLS network. LSRs support label
distribution and label swapping.
LER
A label edge router (LER) resides at the edge of an MPLS network and is connected with another network.
LSP
A label switched path (LSP) is the path along which packets of a FEC travel through an MPLS network.
An LSP is a unidirectional path from the ingress of an MPLS network to the egress. On an LSP, two
neighboring LSRs are called the “upstream LSR” and “downstream LSR” respectively. In Figure 2, LSR B is
the downstream LSR of LSR A; LSR A is the upstream LSR of LSR B.
Figure 2 Diagram for an LSP
LFIB
Labeled packets are forwarded according to the Label Forwarding Information Base (LFIB).
Control plane and forwarding plane
An MPLS node consists of two planes, control plane and forwarding plane.
•The control plane assigns labels, selects routes, creates the LFIB, and establishes and removes LSPs.
•The forwarding plane forwards packets according to the LFIB.
Exp
0
S
19 2223 31
Label TTL
Layer 2 header Layer 3 headerLabel Layer 3 data

3
MPLS network structure
Figure 3 Diagram for the MPLS network structure
As shown in Figure 3, LSRs in the same routing or administrative domain form an MPLS domain.
An MPLS domain consists of the following types of LSRs:
•Ingress LSRs receive and label packets coming into the MPLS domain.
•Transit LSRs forward packets along LSPs to their egress LERs according to the labels.
•Egress LSRs remove labels from packets and forward the packets to their destination networks.
LSP establishment and label distribution
LSP establishment
Establishing LSPs is to bind FECs with labels on each LSR involved and notify its adjacent LSRs of the
bindings, so as to establish the LFIB on each LSR. LSPs can be manually established through configuration,
or dynamically established through label distribution protocols.
•Establishing a static LSP through manual configuration
To establish a static LSP, you must assign a label to the FEC on each LSR along the packet
forwarding path. Establishment of static LSPs consumes fewer resources than dynamic LSP
establishment. However, static LSPs cannot adapt to network topology changes. Therefore, static
LSPs are suitable for small-scale networks with simple, stable topologies.
•Establishing an LSP through a label distribution protocol
Label distribution protocols are MPLS signaling protocols. They can classify FECs, distribute labels,
and establish and maintain 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 BGP and RSVP-TE.
This document discusses LDP only. For more information about LDP, see “LDP.”
NOTE:
In this document, the term
label distribution protocols represents all protocols for label distribution, and the
term
LDP refers to the Label Distribution Protocol defined in RFC 5036.

4
As shown in Figure 4, a dynamic LSP is established in the following procedure:
A downstream LSR classifies FECs according to destination addresses. It assigns a label to a FEC, and
distributes the FEC-label binding to its upstream LSR, which then establishes an LFIB entry for the FEC
according to the binding information. After all LSRs along the packet forwarding path establish a LFIB
entry for the FEC, an LSP is established for packets of this FEC.
Figure 4 Process of dynamic LSP establishment
Label distribution and management
An LSR informs its upstream LSRs of labels assigned to FECs through label advertisement. The label
advertisement modes include downstream unsolicited (DU) and downstream on demand (DoD). The
label distribution control modes include independent and ordered.
Label management specifies the mode for processing a received label binding that is not useful at the
moment. The processing mode, called “label retention mode,” can be either liberal or conservative.
•Label advertisement modes
Figure 5 Label advertisement modes
LSR A LSR B LSR D
LSR C
LSR E LSR F LSR G
LSR H
Ingress Egress
LSP
Label mapping

5
Figure 5 shows the two label advertisement modes, DU and DoD.
{In DU mode, an LSR assigns a label to a FEC and then distributes the FEC-label binding to its
upstream LSR unsolicitedly.
{In DoD mode, an LSR assigns a label to a FEC and distributes the FEC-label binding to its
upstream LSR only when it receives a label request from the upstream LSR.
NOTE:
•The switch supports only the DU mode.
•An upstream LSR and its downstream LSR must use the same label advertisement mode; otherwise, no
LSP can be established.
•Label distribution control modes
Label distribution control modes include independent and ordered.
{In independent mode, an LSR can distribute label bindings upstream at anytime. This means
that an LSR may have distributed a label binding for a FEC to its upstream LSR before it receives
a binding for that FEC from its downstream LSR. As shown in Figure 6, in independent label
distribution control mode, if the label advertisement mode is DU, an LSR will assign labels to its
upstream even if it has not obtained labels from its downstream; if the label advertisement
mode is DoD, the LSR distributes a label to its upstream as long as it receives a label request
from the upstream.
Figure 6 Independent label distribution control mode
{In ordered mode, an LSR distributes its label binding for a FEC upstream only when it receives
a label binding for the FEC from its downstream or it is the egress of the FEC. In Figure 5, label
distribution control is in ordered mode. In this case, if the label advertisement mode is DU, an
LSR will distribute a label upstream only when it receives a label binding for the FEC from its
downstream; if the label advertisement mode is DoD, after an LSR (Transit in this example)
receives a label request from its upstream (Ingress), the LSR (Transit) sends a label request to its
downstream (Egress). Then, after the LSR (Transit) receives the label binding from its
downstream (Egress), it distributes a label binding to the upstream (Ingress).
•Label retention modes
Egress
Transit
DU mode
DoD mode
Ingress
2) Distribute a label to the
upstream unsolicitedly
1) Distribute a label to the
upstream unsolicitedly
1) Request the downstream to
assign a label
3) Request the downstream to
assign a label
2) Assign and distribute a
label to the upstream upon
receiving the request
4) Assign and distribute a
label to the upstream upon
receiving the request

6
Label retention modes include liberal and conservative.
{In liberal mode, an LSR keeps any received label binding regardless of whether the binding is
from the next hop for the FEC or not. This allows for quicker adaptation to route changes but will
waste label resources because LSRs keep extra labels.
{In conservative mode, an LSR keeps only label bindings that are from the next hops for the FECs.
This allows LSRs to maintain fewer labels but makes LSRs slower in adapting to route changes.
NOTE:
The switch supports only the liberal mode.
MPLS forwarding
LFIB
An LFIB comprises the following table entries.
•Next Hop Label Forwarding Entry (NHLFE): Describes the label operation to be performed. It is
used to forward MPLS packets.
•FEC to NHLFE (FTN) map: FTN maps each FEC to a set of NHLFEs at the ingress LSR. The FTN map
is used for forwarding unlabeled packets that need MPLS forwarding. When an LSR receives an
unlabeled packet, it looks for the corresponding FIB entry. If the Token value of the FIB entry is not
Invalid, the packet needs to be forwarded through MPLS. The LSR then looks for the corresponding
NHLFE entry according to the Token value to determine the label operation to be performed.
•Incoming Label Map (ILM): ILM maps each incoming label to a set of NHLFEs. It is used to forward
labeled packets. When an LSR receives a labeled packet, it looks for the corresponding ILM entry.
If the Token value of the ILM entry is not null, the LSR looks for the corresponding NHLFE entry to
determine the label operation to be performed.
NOTE:
FTN and ILM are associated with NHLFE through Token.

7
MPLS data forwarding
Figure 7 MPLS forwarding process diagram
As shown in Figure 7, in an MPLS domain, a packet is forwarded in the following procedure:
1. Router B (the ingress LSR) receives a packet carrying no label. It determines the FEC of the packet
according to the destination address, and searches the FIB table for the Token value. Because the
Token value is not Invalid, Router B looks for the corresponding NHLFE entry that contains the
Token value. According to the NHLFE entry, Router B pushes label 40 to the packet, and forwards
the labeled packet to the next hop LSR (Router C) through the outgoing interface (GE3/0/2).
2. Upon receiving the labeled packet, Router C looks for the ILM entry that contains the label 40 to
get the Token value. Because the Token value is not empty, Router C looks for the corresponding
NHLFE entry containing the Token value. According to the NHLFE entry, Router C swaps the
original label with label 50, and then forwards the labeled packet to the next hop LSR (Router D)
through the outgoing interface (GE3/0/2).
3. Upon receiving the labeled packet, Router D (the egress) looks for the ILM entry according to the
label (50) to get the Token value. Because the Token is empty, Router D removes the label from the
packet. If the ILM entry records the outgoing interface, Router D forwards the packet through the
outgoing interface; if no outgoing interface is recorded, router D forwards the packet according to
the IP header of the packet.
PHP
In an MPLS network, when an egress node receives a labeled packet, it looks up the LFIB, pops the label
of the packet, and then performs the next level label forwarding or performs IP forwarding. The egress
node needs to do two forwarding table lookups to forward a packet: looks up the LFIB twice, or looks up
the LFIB once and the FIB once.
The penultimate hop popping (PHP) feature can pop the label at the penultimate node to relieve the
egress of the label operation burden.
PHP is configured on the egress node. The label assigned by a PHP-capable egress node to the
penultimate hop can be one of the following:

8
•IPv4 explicit null label 0: The egress assigns an IPv4 explicit null label to a FEC and advertises the
FEC-label binding to the upstream LSR. When forwarding an MPLS packet, the upstream LSR
replaces the label at the stack top with the explicit null label and then sends the packet to the egress.
When the egress receives the packet, which carries a label of 0, it does not look up for the LFIB entry
but pops the label stack directly and performs IPv4 forwarding.
•Implicit null label 3: This label never appears in the label stack. The upstream LSR directly performs
a pop operation to the labeled packets that match the implicit null label rather than substitutes the
implicit null label for the original label at the stack top, and forwards the packet to the downstream
egress LSR. The egress directly performs the next level forwarding upon receiving the packet.
LDP
LDP is used to establish LSPs dynamically. Using LDP, LSRs can map network layer routing information to
data link layer switching paths.
Basic concepts of LDP
•LDP session
LDP sessions are established between LSRs based on TCP connections and used to exchange
messages for label binding, label releasing, and error notification.
•LDP peer
Two LSRs using LDP to exchange FEC-label bindings are LDP peers.
LDP message type
LDP messages fall into the following types:
•Discovery messages—declare and maintain the presence of LSRs.
•Session messages—establish, maintain, and terminate sessions between LDP peers.
•Advertisement messages—create, alter, and remove FEC-label bindings.
•Notification messages—provide advisory information and notify errors.
LDP session, advertisement, and notification messages use TCP for reliability. Discovery messages use
UDP for efficiency.
LDP operation
LDP goes through four phases in operation:
1. Discovery
Each LSR sends hello messages periodically to notify neighboring LSRs of its presence. In this way,
LSRs can automatically discover their LDP peers. LDP provides two discovery mechanisms:
{Basic discovery mechanism—Discovers directly connected LSRs. An LSR periodically sends LDP
link Hello messages to multicast address 224.0.0.2 that identifies all routers on the subnet to
advertise its presence.
{Extended discovery mechanism—Discovers indirectly connected LDP peers. An LSR
periodically sends LDP Hello messages to a given IP address so that the LSR with the IP address
can discover the LDP peer.
2. Session establishment and maintenance
After an LSR finds a LDP peer, they start to establish a session through the following two steps:
{Establish a TCP connection between them.

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{Initialize negotiation of session parameters such as the LDP version, label advertisement mode,
and Keepalive interval.
After establishing a session between them, the two LDP peers send Hello messages and Keepalive
messages to maintain the session.
3. LSP establishment and maintenance
LDP sends label requests and label binding messages between LDP peers to establish LSPs.
For the LSP establishment process, see “LSP establishment and label distribution.”
4. Session termination
An LSR terminates its LDP session with an LDP peer in the following cases:
{All Hello adjacencies are deleted between the two peers
LDP peers periodically send Hello messages to indicate that they intend to keep the Hello
adjacency. If an LSR does not receive any Hello message from a peer before the Hello timer
expires, it deletes the Hello adjacency with this peer. An LDP session has one or more Hello
adjacencies. When the last Hello adjacency for the session is deleted, the LSR will send a
Notification message to terminate the LDP session.
{Loss of session connectivity
An LSR determines the integrity of an LDP session according to the LDP PDU (which carries one
or more LDP messages) transmitted on the session. Before the Keepalive timer times out, if two
LDP peers have no information to exchange, they can send Keepalive messages to each other
to maintain the LDP session. If an LSR does not receive any LDP PDU from its peer during a
Keepalive interval, it closes the TCP connection and terminates the LDP session.
{Receiving a shutdown message from the peer
An LSR can also send a Shutdown message to its LDP peer to terminate the LDP session.
Therefore, when receiving the Shutdown message from an LDP peer, an LSR terminates the
session with the LDP peer.
Protocols
MPLS related protocols include:
•RFC 3031, Multiprotocol Label Switching Architecture
•RFC 3032, MPLS Label Stack Encoding
•RFC 5036, LDP Specification
MPLS configuration task list
Complete the following tasks to configure MPLS:
Task Remarks
Enabling the MPLS function Required
Configuring a static LSP Required
Use either the static
or dynamic LSP
configuration
method
Establishing dynamic LSPs
through LDP
Configuring MPLS LDP capability Required
Configuring local LDP session
parameters Optional
Configuring remote LDP session
parameters Optional

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Task Remarks
Configuring PHP Optional
Configuring the policy for triggering
LSP establishment Optional
Configuring the label distribution
control mode Optional
Configuring LDP loop detection Optional
Configuring LDP MD5 authentication Optional
Configuring LDP label filtering Optional
Maintaining LDP sessions Configuring BFD for MPLS LDP Optional
Resetting LDP sessions Optional
Managing and optimizing MPLS
forwarding
Configuring MPLS MTU Optional
Configuring TTL processing mode at
ingress Optional
Sending back ICMP TTL exceeded
messages for MPLS TTL expired
packets
Optional
Configuring LDP GR Optional
Configuring MPLS statistics
collection and reading
Setting MPLS statistics reading
interval Optional
Inspecting LSPs
Configuring MPLS LSP ping Optional
Configuring MPLS LSP tracert Optional
Configuring BFD for LSPs Optional
Configuring periodic LSP tracert Optional
Enabling MPLS trap Optional
NOTE:
Layer 3 interfaces such as Layer 3 Ethernet interfaces and VLAN interfaces support MPLS. Tunnel
interfaces and Layer 2 interfaces do not support MPLS.
Enabling the MPLS function
Enable MPLS on all routers before you can configure other MPLS features.
Configuration prerequisites
Before you enable MPLS, complete the following tasks:
•Configure link layer protocols to ensure the connectivity at the link layer.
•Assign IP addresses to interfaces so that all neighboring nodes can reach each other at the network
layer.
•Configure static routes or an IGP protocol for the LSRs to communicate with each other.

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Configuration procedure
To enable MPLS:
To do… Use the command…
Remarks
Enter system view system-view —
Configure the MPLS LSR ID mpls lsr-id lsr-id Required
Not configured by default
Enable MPLS globally and enter
MPLS view mpls Required
Not enabled by default
Return to system view quit —
Enter interface view interface interface-type
interface-number —
Enable MPLS for the interface mpls Required
Not enabled by default
NOTE:
A
n MPLS LSR ID is in the format of an IP address and must be unique within an MPLS domain. HP
recommends using the IP address of a loopback interface on an LSR as the MPLS LSR ID.
Configuring a static LSP
The principle of establishing a static LSP is that the outgoing label of an upstream LSR is the incoming
label of its downstream LSR.
Configuration prerequisites
Before you configure a static LSP, complete the following tasks:
•Determine the ingress LSR, transit LSRs, and egress LSR for the static LSP.
•Enable MPLS on all these LSRs.
•Make sure that the ingress LSR has a route to the FEC destination. This is not required on the transit
LSRs and egress LSR.
Configuration procedure
To configure a static LSP:
To do… Use the command…
Remarks
Enter system view system-view —
Configure a static LSP taking the
current LSR as the ingress
static-lsp ingress lsp-name
destination dest-addr { mask |
mask-length } { nexthop
next-hop-addr | outgoing-interface
interface-type interface-number }
out-label out-label
Required

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To do… Use the command… Remarks
Configure a static LSP taking the
current LSR as a transit LSR
static-lsp transit lsp-name
incoming-interface interface-type
interface-number in-label in-label
{ nexthop next-hop-addr |
outgoing-interface interface-type
interface-number } out-label
out-label
Required
Configure a static LSP taking the
current LSR as the egress
static-lsp egress lsp-name
incoming-interface interface-type
interface-number in-label in-label
Required
NOTE:
•When you configure a static LSP on the ingress LSR, the next hop or outgoing interface specified must be
consistent with the next hop or outgoing interface of the optimal route in the routing table. If you
configure a static IP route for the LSP, be sure to specify the same next hop or outgoing interface for the
static route and the static LSP.
•For an ingress or transit LSR, do not specify the public address of an interface on the LSR as the next hop
address.
•For information about configuring a static IP route, see
Layer 3—IP Routing Configuration Guide .
Establishing dynamic LSPs through LDP
Configuring MPLS LDP capability
To configure MPLS LDP capability:
To do… Use the command…
Remarks
Enter system view system-view —
Enable LDP capability globally and
enter MPLS LDP view mpls ldp Required
Not enabled by default
Configure the LDP LSR ID lsr-id lsr-id Optional
MPLS LSR ID of the LSR by default
Return to system view quit —
Enter interface view interface interface-type
interface-number —
Enable LDP capability for the
interface mpls ldp Required
Not enabled by default