MPLS NSN Training Day 1

8/9/2019 MPLS NSN Training Day 1

http://slidepdf.com/reader/full/mpls-nsn-training-day-1 1/96

MPLSMultiprotocol Label Switching

Mitrabh Shukla

National IP Manager



2 © Nokia Siemens Networks MPLS / Mitrabh Shukla

For i nternal use

Agenda

Business Drivers for MPLS

MPLS Definition

MPLS Capabilities

MPLS Concepts & ComponentsBasic MPLS Forwarding

Verifying MPLS

Summary and Benefits of MPLS (Control & Forwarding Plane

Separation)






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Customer Requirements

Businesses are building on IP Businesses need private

IP services

Customers

Suppliers

Partners

Telecommuters

RemoteOffices

IP Intranet IP Extranet




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Value-Added

IP Services

Problem:

How to Build a Network

that Can Deliver these

Services and SLAs

Service Provider Requirements

Growth: IP Connection

Internet, Intranet,

Extranet

Multimedia

Content

Hosting

Service Portfolio

Revenue: Transport

Frame Relay, ATM,

Managed Services

Managed

Intranets

Private

Voice Networks

Profit: IP VAS

Hosting, Voice, Video,

ASP’s




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The Solution - MPLS

MULTI-PROTOCOL LABEL SWITCHING

A mechanism that delivers the best of both worlds:

• PRIVACY and QOS of ATM, Frame Relay

• FLEXIBILITY and SCALABILITY of IP

Foundation for IP business services• Flexible grouping of users and value-added services

Low cost managed IP services

• scales to large and small private networks



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What Is MPLS?

Multi Protocol Label Switching

MPLS is an efficient encapsulation mechanism

Uses ―labels‖ appended to packets (IP packets, AAL5 frames) fortransport of data

MPLS packets can run on other Layer 2 technologies such as ATM,

FR, PPP, POS, EthernetOther Layer 2 technologies can be run over anMPLS network

Labels can be used as designators

• For example—IP prefixes, ATM VC, or a bandwidthguaranteed path

MPLS is a technology for delivery of IP services



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Original Motivation of MPLS

Allow core routers/networking devices to switch packets based

on some simplified header

Provide a highly scalable mechanism that was topology drivenrather than flow driven

Leverage hardware so that simple forwarding paradigm can be

usedIt has evolved a long way from the original goal

• Hardware became better and looking up longest best matchwas no longer an issue

• By associating labels with prefixes, groups of sites orbandwidth paths or light paths new services such as MPLSVPNs and traffic engineering, GMPLS were now possible





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MPLS concepts

Packet forwarding is done based on labels

Labels assigned when the packet enters the network

Labels inserted between layer 2 and layer 3 headers

MPLS nodes forward packets based on the labelSeparates ROUTING from FORWARDING

• Routing uses IP addresses

• Forwarding uses Labels

Labels can be stacked



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MPLS Concepts

Create new services via flexible classification

Provide the ability to setup bandwidth guaranteed paths

Enable ATM switches to act as routers

At Edge:

• Classify packets

• Label them

• Label imposition

In Core:

• Forward using labels

(as opposed to IP addr)• Label indicates service class

and destination

• Label swapping or switching

Label Switch Router (LSR)

• Router

• ATM switch + label

switch controller Label Distribution Protocol

Edge Label Switch

Router (ATM Switch or

Router)

At Edge:

• Remove labels and forward

packets• Label disposition




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MPLS Operation

1a. Existing Routing Protocols (e.g. OSPF, IS-IS)Establish Reachability to Destination Networks

1b. Label Distribution Protocol (LDP)

Establishes Label to Destination

Network Mappings

2. Ingress Edge LSR Receives Packet,

Performs Layer 3 Value-Added Services,

and ―Labels‖ Packets3. LSR Switches Packets

Using Label Swapping

4. Edge LSR at

Egress RemovesLabel and Delivers

Packet






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Label Header (Shim)

Label

1 2 3 4 5 6 7 8

EXP S

TTL

Bit

2

3

4

1

B y t e

Label

EXP

S

TTL

Label Value (20 bits)

Class of Service (3 bits)

Bottom of Stack (1 bit)

Time to Live

•Can be used over Ethernet, 802.3, or PPP links

•Ethertype 0x8847

•One for unicast, one for multicast

•Four octets per label in stack




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Relevant MPLS Capabilities

The ability to FORWARD on and STACK LABELS allowsMPLS to provide some useful features including:

IP+ATM Integration

• Provides Layer 3 intelligence in ATM switches

Virtual Private Networks

• Layer 3 – Provider has knowledge of customer routing

• Layer 2 – Provider has no knowledge of customerrouting

Traffic Engineering

• Force traffic along predetermined paths




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MPLS VPN – Layer 3

Private, connectionless IP VPNs

Outstanding scalability

Customer IP addressing freedom

Multiple QoS classes

Secure support for intranets and

extranetsEasy to provide Intranet/Extranet/3rd

Party ASP

Support over any access or backbonetechnology

VPN C

VPN A

VPN B

VPN C

VPN AVPN B

VPN C

VPN A

VPN B

VPN C

VPN AVPN B

Connection-Oriented

VPN Topology

VPN C

VPN A

VPN B

VPN C

VPN AVPN B

VPN C

VPN A

VPN BVPN C

VPN A

VPN BConnectionlessVPN Topology

IP PacketVPN

Label

IGP

Label

Determines PE

Router

Determines VPN on

PE Router




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Single network

supporting multiple VPNsSeparately engineered

private IP networksvs

Build once,Sell once

Build once,Sell many

Why Providers like MPLS VPN…

MPLS VPNNetwork




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MPLS VPN – Layer 2

Attachment

Circuit

AttachmentCircuit

L2 Frames

L2 Pseudowire/Emulated VC

Additional Capabilities:

Virtual leased line service

Offer ―PVC-like‖ Layer 2-based

service

Reduced cost—consolidate

multiple core technologies

into a single packet-based

network infrastructure

Simpler provisioning of L2

services

Attractive to Enterprise that

wish keep routing private

L2 FrameVC

Label

Tunnel

Label

Determines PE

Router end point

Determines VC inside

the tunnel




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Traffic Engineering

Route chosen by

IP routing protocol

Route specified by

traffic engineering

Why traffic engineer?

• Optimise link utilisation

• Specific paths by customer or class

• Balance traffic load

Traffic follows pre-specified pathPath differs from normally routed path

Controls packet flows across a L2 or L3network

IP PacketVPN

Label

IGP

Label

TE

Label

Determines LSP next

hop contrary to IGP




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MPLS Components

Edge Label Switching Routers (ELSR or PE)

• Label previously unlabeled packets - at the beginning of aLabel Switched Path (LSP)

• Strip labels from labeled packets - at the end of an LSP

Label Switching Routers (LSR or P)

• Forward labeled packets based on the information carried bylabels




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MPLS Components

LSR LSR

LSR LSR

ELSR

ELSR

P Network(Provider Control)

PECE CEPE

ELSR

ELSR

C Network(Customer Control)

C Network(Customer Control

P




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MPLS Forwarding




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MPLS: Forwarding




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MPLS: Forwarding

Existing routing protocols (e.g. OSPF, IGRP) establish routes




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MPLS: Forwarding

Label Distribution Protocol (e.g., LDP) establishes label toroutes mappings




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MPLS: Forwarding

Label Distribution Protocol (e.g., LDP) creates LFIB entries onLSRsIN OUT I/F MAC

Null - E0/0 aa-00-bb

Null - E0/1 aa-00-cc

IN OUT I/F MAC

16 32 S0/0 aa-00-bb

18 27 S0/0 aa-00-cc

IN OUT I/F MAC

32 64 S0/0 aa-00-bb

27 18 S0/1 aa-00-cc

IN OUT I/F MAC

64 POP S0/0 aa-00-bb

65 POP S0/1 aa-00-cc




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MPLS: Forwarding

Ingress edge LSR receives packet, performs Layer 3 value-added

services, and “label” packets

IN OUT I/F MAC



IN OUT I/F MAC

16 32 S0/0 aa-00-bb

18 27 S0/0 aa-00-cc

IN OUT I/F MAC

32 64 S0/0 aa-00-

bb

27 18 S0/1 aa-00-

cc

IN OUT I/F MAC






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MPLS: Forwarding

LSRs forward labelled packets using label swapping

IN OUT I/F MAC



IN OUT I/F MAC

16 32 S0/0 aa-00-bb

18 27 S0/0 aa-00-cc

IN OUT I/F MAC

32 64 S0/0 aa-00-bb

27 18 S0/1 aa-00-ccIN OUT I/F MAC






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MPLS: Forwarding

Edge LSR at egress removes remaining label* and delivers

packet

* Pentulimate hop popping actually occurs. There may may not necessarily be a label in the

packet at the ultimate or egress LSR.

IN OUT I/F MAC



IN OUT I/F MAC

16 32 S0/0 aa-00-bb

18 27 S0/0 aa-00-cc

IN OUT I/F MAC

32 64 S0/0 aa-00-bb

27 18 S0/1 aa-00-cc

IN OUT I/F MAC






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Provider Network

Visual Objective

LDP and Label Switching onCore Interfaces

CEF and MPLS onCore Routers

Customer Networks

P routers

ASBRs

CE routers

Route

Reflectors

ASBR

RR

PE

CE

Internets

PE routers

Customer Networks

ASBR

RR

PE

CE

Internets

PP




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Label Switching Devices

Edge Label Switching Routers (ELSR)

• label previously unlabeled packets at the beginning (ingress) of a

Label Switched Path (LSP)• strip labels from labeled packets at the end (egress) of LSP

Label Switching Routers (LSR)

• forward labeled packets based on the label - not IP addresses

Label Switching Routers(Router or ATM Switch)

Edge Label Switching Routers

PE1 PE2 CE2CE1 P




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MPLS Forwarding Operations

Label Imposition: add label stack to unlabeled packet (e.g. IP

packet) at edge (push)Label Forwarding: use label on packet to select next hop andlabel stack operation (replace, replace & push)

Label Disposition: Remove (last) label from packet (pop)




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Agenda

What are the MPLS Technologies and How Do I Deploy Them?

• Control Plane

• Forwarding Plane

What Do I Need to Consider in Deploying MPLS?

How Do I Troubleshoot MPLS?




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FORWARDING Plane

MPLS Technologies

IP Routing Protocols

IP Routing Table

Label Information Base

Exchange of

routing information

Exchange of

label bindings

Incoming unlabeled

packets

CEF

Label Forwarding

Information Base

Incoming labeled

packets

Outgoing labeled or

unlabeled packets

Outgoing labeled or

unlabeled packets

CONTROL Plane

Forwarding Information Base

MPLS IP Routing Control

MPLS C l Pl




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MPLS Control Plane

Enable CEF

CEF builds the FIB which provides the structure for thelabel forwarding mechanism• PE1(config)#ip cef

Enable a label distribution protocol• NOTE: If LDP is not specifically configured, TDP is active by default

• PE1(config)#mpls label protocol ldp

Enable MPLS on interfaces• PE1(config)#interface e0/0• PE1(config-if)#mpls ip

• PE1(config-if)#mpls label protocol ldp

At this point the LIB is constructed and the LDP/TDP process isstarted

Global enable

or i/f by i/f

Global enable

or i/f by i/f

C t t f th




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Tags assigned by other router/s.

These tags will be on packets going OUT

Tags assigned by this router.These tags will be on packets coming IN

PE2#show mpls ldp binding

tib entry: 10.131.0.0/24, rev 50

remote binding: tsr: 10.131.31.252:0, tag: imp-null

tib entry: 10.131.31.220/30, rev 30

local binding: tag: 20

remote binding: tsr: 10.131.63.251:0, tag: 17


Contents of theLabel Information Base (LIB)

P t l t Di t ib t L b l Bi di



38 © Nokia Siemens Networks MPLS / Mitrabh ShuklaFor i nternal use

Protocols to Distribute Label Bindings

Label Distribution Protocol (LDP)

(or Tag Distribution Protocol (TDP))• For MPLS forwarding along normally routed paths

Border Gateway Protocol (BGP)

• For MPLS virtual private network (VPN)

Resource Reservation Protocol (RSVP)

• For MPLS traffic engineering

H D LDP Diff f TDP?




How Does LDP Differ from TDP?

LDP is very similar to TDP

• Purpose is the same: advertise label bindings

• Some encoding differs

LDP has extras

•Session backoff mechanism

• MD5 to protect against spoofing

• Path vector based loop detection mechanism




LDP Discovery and Session Establishment

Discovery• UDP Hellos multicast to 224.0.0.2, port 646

(TDP hellos to 255.255.255.255, port 711)

• Used to discover and maintain the presence of new peers

Session Establishment• LDP session is established over TCP

• R1 and R2 negotiate session parameters(advertisement mode, label range, and so on)

• Sessions maintained with LDP hello and TCP keepalive

R1 R2

Hello, R1:0

Hello, R2:0

LDP R t ID




LDP Router-ID

LDP Router-ID is the IP address of:

• loopback in up/up state with the highest ip address

• if no loopback, the first interface in up/up state

Force with the command:

mpls ldp router-id Loopback0

LDP S i




Platform-wide examples of one LDP session per

label space between two routers

LDP Sessions

R1 R2

Hello, R1:0

Hello, R2:0

R1 R2

Hello, R1:0

Hello, R2:0

LDP session between R1 and R2• 1 TCP connection• 3 discovery sources

LDP session between R1 and R2• 1 TCP connection• 1 discovery source

• Peers exchange LDP messages advertising labels

between LSRs

• TCP used for reliable transport

V if LDP S i




P1#show mpls ldp discovery detailLocal LDP Identifier:

10.131.31.252:0Discovery Sources:Interfaces:

Ethernet0/0 (ldp): xmit/recvHello interval: 5000 ms; Transport IP addr: 10.131.31.252

LDP Id: 10.131.31.251:0Src IP addr: 10.131.31.229; Transport IP addr: 10.131.31.251Hold time: 15 sec; Proposed local/peer: 15/15 sec

Ethernet1/0 (ldp): xmit/recv

Hello interval: 5000 ms; Transport IP addr: 10.131.31.252LDP Id: 10.131.63.252:0Src IP addr: 10.131.31.218; Transport IP addr: 10.131.63.252Hold time: 15 sec; Proposed local/peer: 15/15 sec


Hello interval: 5000 ms; Transport IP addr: 10.131.31.252LDP Id: 9.9.9.9:0; no route to transport addrSrc IP addr: 10.131.31.234; Transport IP addr: 9.9.9.9Hold time: 15 sec; Proposed local/peer: 15/15 sec

Verify LDP Sessions

LDP session requires IGP reachability

between these 2 addresses

else ―no route‖ problem

LDP Label Advertisement Modes




LDP Label Advertisement Modes

Downstream Unsolicited

(default for Cisco Routers):• LSR advertises label for prefix when ready to label switch packets

for the prefix

• Provides local and rapid response to route changes

Downstream on Demand(used with ATM to conserve vpi/vci space):

• Upstream LSR requests label for new/revised route

• LSR only advertises label on request from upstream peer

• LSRs interact to respond to route changes

Verify LDP Remote Bindings




Verify LDP Remote Bindings

P1#show mpls ldp neighborPeer LDP Ident: 10.131.63.252:0; Local LDP Ident 10.131.31.252:0

TCP connection: 10.131.63.252.11025 - 10.131.31.252.646

State: Oper; Msgs sent/rcvd: 1078/1080; Downstream

Up time: 15:29:17

LDP discovery sources:

Ethernet1/0, Src IP addr: 10.131.31.218

Addresses bound to peer LDP Ident:10.131.63.230 10.131.31.218 10.131.63.221 10.131.63.233

10.131.63.252

Peer LDP Ident: 10.131.31.251:0; Local LDP Ident 10.131.31.252:0

TCP connection: 10.131.31.251.646 - 10.131.31.252.11015

State: Oper; Msgs sent/rcvd: 1082/1085; Downstream

Up time: 15:29:13

LDP discovery sources:

Ethernet0/0, Src IP addr: 10.131.31.229Addresses bound to peer LDP Ident:

10.131.31.229 10.131.31.241 10.131.31.251




MPLS Forwarding Plane

FIB: Forwarding Information Base, activated when

CEF is enabled• used for incoming unlabeled packets

LFIB: Label Forwarding Information Base

• used for incoming labeled packets

untagged packet

tagged packet

PE1 P1 P229packet 43packet

untagged packet FIB

tagged packet LFIB

untagged packet

tagged packet

Populating the LFIB




Populating the LFIB

LIB holds:• Local labels (assigned by this router)• Remote labels (learned from LDP neighbors)

LFIB updates are triggered by:• 1) Routing changes• 2) Label advertisements from neighbors

IP Routing Table

LIB LFIB2. LDP Label Message

Add Label

1. Routing Change

Find Label

Change/add Label

Animated

Contents of the FIB Detail




Contents of the FIB Detail

PE1#show ip cef 10.131.63.25310.131.63.253/32, version 27, epoch 0, cached adjacency 10.131.31.2330 packets, 0 bytestag information set, sharedlocal tag: 29

fast tag rewrite with Et0/0, 10.131.31.233, tags imposed: {26}via 10.131.31.233, Ethernet0/0, 8 dependenciesnext hop 10.131.31.233, Ethernet0/0valid cached adjacencytag rewrite with Et0/0, 10.131.31.233, tags imposed: {26}

PE1#show ip cef 10.131.31.25210.131.31.252/32, version 22, epoch 0, cached adjacency 10.131.31.2330 packets, 0 bytestag information set

local tag: 24via 10.131.31.233, Ethernet0/0, 0 dependencies

next hop 10.131.31.233, Ethernet0/0valid cached adjacencytag rewrite with Et0/0, 10.131.31.233, tags imposed: {}

tagged

untagged

Contents of the LFIB




Contents of the LFIB

#show mpls forwarding-tableLocal Outgoing Prefix Bytes tag Outgoing Next Hop

tag tag or VC or Tunnel Id switched interface

16 Pop tag 10.131.63.240/30 0 Et0/0 10.131.63.229

17 Pop tag 10.131.31.224/30 0 Et0/0 10.131.63.229

18 Pop tag 10.131.63.220/30 0 Et0/0 10.131.63.229

19 Pop tag 10.131.31.228/30 0 Et1/0 10.131.31.245

20 17 10.131.31.220/30 0 Et0/0 10.131.63.229

18 10.131.31.220/30 0 Et1/0 10.131.31.245

21 18 10.131.31.240/30 0 Et0/0 10.131.63.229

16 10.131.31.240/30 0 Et1/0 10.131.31.245

23 23 10.131.31.251/32 0 Et0/0 10.131.63.229

23 10.131.31.251/32 0 Et1/0 10.131.31.245

24 Pop tag 10.131.63.251/32 5617 Et0/0 10.131.63.229

25 29 10.131.63.255/32 143678 Et0/0 10.131.63.229

The penultimate hop pop

Contents of the LFIB Detail




Contents of the LFIB Detail

HDLC header

0x8847 = ethertype MPLS

MPLS Label

0x0001C = Label (28 decimal)0x0 = 0000 (binary)

3 experimental bits

1 S bit

0x00 = TTL

MAC/Encaps

MAC = number of bytes of Layer2 header

Encaps = total number of bytes of Layer2 and label(s)

PE1#show mpls forwarding-table 10.131.63.253 detail

Local Outgoing Prefix Bytes tag Outgoing Next Hop

tag tag or VC or Tunnel Id switched interface

29 28 10.131.63.253/32 0 Et0/0 10.131.31.233

MAC/Encaps=14/18, MRU=1508, Tag Stack{28}

AABBCC007003AABBCC0071008847 0001C000No output feature configured

Per-packet load-sharing, slots:0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Control and Forwarding Planes In Action




10.131.0.0/24

Control and Forwarding Planes In Action

CE1

PE1 P1

CE2

PE2P2

10.131.0.1

10.131.0.13610.131.0.120

10.131.0.1

10.131.0.1

Animated

Penultimate Hop Pop (remove top label)controlled by implicit null

(label value = 1 for TDP, 3 for LDP)

implicit null label 36 label 20

Where did

implicit nu ll

come from?

P1 LFIB for

10.131.0.1

pop20

OutIn

P2 LFIB for

10.131.0.1

2036

OutIn

PE1 LFIB for

10.131.0.1

OutIn

PE2 LFIB for

10.131.0.1

3624

OutIn

show mpls forwarding

PE1 LIB for

10.131.0.1

-Imp null

OutIn

show mpls ldp binding




Label-switching or CEF Switching?

Label Operations• Pop - remove the top tag• Push - add a top tag• Swap - pop and push• Aggregate - pop and do IP lookup

Function Table Lookup Locationip-to-label(imposition)

CEF CE to PE

label-to-label(swapping)

LFIBPE to PP to P

P to PElabel-to-IP(disposition)

LFIB PE to CE

MPLS Key Points




MPLS Key Points

Route Forwarding Table

show ip route

FIB-Forwarding Information Base

show ip cef

LFIB-Label Forwarding Information Baseshow mpls forwarding

OSPF Database

show ip ospf database

BGP Databaseshow ip bgp

Routing updates received

and stored in databases

Best Path selected & stored

other Databasesshow rip, eigrp, etc.

LIB-Label Information Base

show mpls ldp binding

CEF builds FIB with Adjacency Info

LDP builds LIB with all MPLS Routes

MPLS builds forwarding table

with best label path

Normal Routing (not changed)

MPLS




MTU Considerations

MTU Path Discovery may not work

• Some hosts may not support it

• ICMP messages may be blocked (firewalls or policy)

Animated

1) 2619 bytes DF bit set

2) ICMP fragmentation needed

DF set next hop MTU=1500

3) 1500 bytes DF bit set 1500 bytes DF bit set

MTU 4470 MTU 1500

MTU Path Discovery

DF=Do not fragment

Traceroute in IP Network




Traceroute in IP Network

10.1.2.1 TTL = 255

TTL exceeded

10.1.2.1 10.1.1.1

TTL=0

10.1.2.1 TTL = 254

TTL exceeded

10.1.2.1 TTL = 255

TTL exceeded

10.1.2.1 TTL = 254

TTL exceeded

10.1.2.1 TTL = 254

TTL exceeded

10.1.2.1 TTL = 255

TTL exceeded

10.1.2.1 TTL = 252

port unreachable

10.1.2.1 TTL = 253

port unreachable

10.1.2.1 TTL = 255

port unreachable

10.1.2.1 TTL = 254

port unreachable

udp port

35678?TTL=0 TTL=0

10.1.1.1 TTL=3 10.1.1.1 TTL=2 10.1.1.1 TTL=110.1.1.1 TTL=44

10.1.1.1 TTL=11

10.1.1.1 TTL=110.1.1.1 TTL=22

10.1.1.1 TTL=2 10.1.1.1 TTL=110.1.1.1 TTL=33

ICMP Probes to UDP port 35678

Traceroute in MPLS Network




Traceroute in MPLS Network

P router may not have knowledge of BGP routes(certainly doesn’t know VPN label)

Original label stack is pushed onto ICMP packet andforwarded (draft-ietf-mpls-icmp)

BGP RID1.1.1.2

BGP RID1.1.1.1

LFIB

Inlabel

prefix OutI/F

Outlabel

- 10.1.1.0/24 0 26

LFIB

Inlabel

prefix OutI/F

Outlabel

26 1.1.1.2/32 0 pop

LFIB

Inlabel

prefix OutI/F

Outlabel

32 10.1.1.0/24 0 -

10.1.2.1 10.1.1.1

PE PEP

MPLS Network

No entry for 10.1.1.0

Traceroute in MPLS Network Example




BGP RID1.1.1.2

BGP RID1.1.1.1

10.1.2.1 10.1.1.1

PE PEP

Traceroute in MPLS Network Example

10.1.2.1 TTL = 255TTL exceeded

TTL=0

10.1.2.1 TTL = 253

TTL exceeded

10.1.2.1 TTL = 254

TTL exceeded

10.1.2.1 TTL = 255

TTL exceeded

10.1.1.1 ?!

1.1.1.2 TTL=0

TTL exceeded

10.1.1.1 TTL=11

10.1.1.1 TTL=110.1.1.1 TTL=22

ICMP Probes

Process repeats until port unreachable returned by 10.1.1.1

Animated

P#debug ip icmp

ICMP packet debugging is on

00:02:08: MPLS: ICMP: time exceeded (time to live)

sent to 1.1.1.2 (dest was 10.1.1.1)

Agenda




Agenda

What are the Basics of MPLS?


• MTU

• Traceroute/Ping


Agenda




Agenda

What are the Basics of MPLS?

What are the MPLS Technologies and How Do I Deploy Them?



Troubleshoot MPLS




Troubleshoot MPLS

Quick Checks

• Is CEF enabled?show ip cef

• Is MPLS enabled on interfaces?show mpls interfaces

• Is MPLS enabled on interfaces?show mpls forwarding-table

MPLS Control Plane Troubleshooting (LDP/TDP)

MPLS Forwarding Plane Troubleshooting

Verify MPLS - Troubleshooting




Verify MPLS Troubleshooting

First see if you are getting labels assigned

If not then verify these items:

• Verify Routing Protocol Is Running

• Verify CEF Switching

• Verify MPLS

• Ping the Neighbors

• Verify Label Distribution• Verify Label Bindings

• Verify Labels Are Set

Check Routing To Neighbors (1 of 2)





RR1#sh ip protocolsRouting Protocol is "ospf 100"

Outgoing update filter list for all interfaces is not setIncoming update filter list for all interfaces is not setRouter ID 10.131.31.255

Number of areas in this router is 1. 1 normal 0 stub 0 nssaMaximum path: 4Routing for Networks:10.131.31.0 0.0.0.255 area 0

Passive Interface(s):Loopback0

Routing Information Sources:Gateway Distance Last Update10.131.63.255 110 02:24:1510.131.63.252 110 02:24:1510.131.63.251 110 02:24:1510.131.31.255 110 02:24:15

10.131.31.252 110 02:24:1510.131.31.251 110 02:24:15

10.132.1.1 110 02:24:15Distance: (default is 110)

continued

Routers in same OSPF area






Routing Protocol is "bgp 100"Outgoing update filter list for all interfaces is not set

Incoming update filter list for all interfaces is not setRoute Reflector for address family IPv4 Unicast, 5 clientsRoute Reflector for address family IPv6 Unicast, 5 clients

Route Reflector for address family VPNv4 Unicast, 5 clientsRoute Reflector for address family IPv4 Multicast, 5 clientsIGP synchronization is disabledAutomatic route summarization is disabledNeighbor(s):Address FiltIn FiltOut DistIn DistOut Weight RouteMap

10.131.31.25010.131.31.25110.131.31.25210.131.63.25110.131.63.252

Maximum path: 1

Routing for Networks:Routing Information Sources:

Gateway Distance Last Update10.131.63.252 200 02:24:0610.131.31.252 200 00:27:1910.131.31.250 200 02:24:01

Distance: external 20 internal 200 local 200

BGP Peers

Check CEF Configuration




Check CEF Configuration

Bad (CEF not enabled)• #show ip cef

• %CEF not running

• Prefix Next Hop Interface

Good (CEF enabled)• #show ip cef• Prefix Next Hop Interface• 0.0.0.0/0 drop Null0 (default route handler entry)

• 0.0.0.0/32 receive• 10.131.0.0/24 10.131.31.221 Ethernet0/0• 10.131.1.0/24 10.131.31.221 Ethernet0/0

Verify CEF Switching




e y C S tc g

#show ip cef 10.10.10.4 detail10.10.10.4/32, version 154, cached adjacency to Serial0/1.1

0 packets, 0 bytestag information set

local tag: 20

fast tag rewrite with Se0/1.1, point2point, tags imposed {22}

via 10.1.1.5, Serial0/1.1, 0 dependenciesnext hop 10.1.1.5, Serial0/1.1

valid cached adjacencytag rewrite with Se0/1.1, point2point, tags imposed {22}

Check Interface Configuration




g

Is this all the interfaces you should have?• #show mpls interfaces

• Interface IP Tunnel Operational

• Ethernet0/0 Yes (ldp) No Yes

• Ethernet1/0 Yes (ldp) No Yes

Ping the Neighbors




g g

#ping 10.10.10.6

Type escape sequence to abort.Sending 5, 100-byte ICMP Echos to 10.10.10.6, timeout is 2

seconds:!!!!!Success rate is 100 percent (5/5), round-trip min/avg/max =56/56/60 ms

Verify MPLS




y

#show mpls interfaces

Interface IP Tunnel Operational

(...)Serial0/1.1 Yes (tdp) Yes Yes

Serial0/1.2 Yes Yes NoSerial0/1.3 Yes (tdp) Yes Yes(...)

Verify Label Distribution




y

PE#show mpls ldp discovery

Local TDP Identifier:10.10.10.3:0

Discovery Sources:Interfaces:

Serial0/1.1 (tdp): xmit/recvTDP Id: 10.10.10.1:0



Verify Label Bindings




y g

#show mpls ldp binding

(...)

10.10.10.1/32

out label: imp-null lsr: 10.10.10.1:0out label: 20 lsr: 10.10.10.6:0out label: 19 lsr: 10.10.10.2:0

10.10.10.2/32

out label: 18 lsr: 10.10.10.1:0out label: 21 lsr: 10.10.10.6:0out label: imp-null lsr: 10.10.10.2:0

10.10.10.3/32

out label: 19 lsr: 10.10.10.1:0out label: 22 lsr: 10.10.10.6:0out label: 22 lsr: 10.10.10.2:0

(...)

Verify Labels Are Set




y

#traceroute 10.10.10.4

Type escape sequence to abort.Tracing the route to 10.10.10.4

1 10.1.1.21 [MPLS: Label 25 Exp 0] 296 msec 256 msec 244 msec2 10.1.1.5 [MPLS: Label 22 Exp 0] 212 msec 392 msec 352 msec

3 10.1.1.14 436 msec * 268 msec

Use this command with “show mpls forwarding-table” tocompare Label values.

MPLS Control Plane Troubleshooting




g

MPLS Control Plane is LDP/TDP

• Are all LDP neighbors up?

• Do the LDP neighbors have IGP reachability?

– Ping the Neighbors

– Verify Routing Protocol Is Running

• Are they configured properly? (same as above)

• Are you getting label bindings?

Verify LDP Neighbor Adjacency




y g j y

Are these all of your neighbors?

#show mpls ldp neighborPeer LDP Ident: 10.131.63.251:0; Local LDP Ident 10.131.31.251:0

TCP connection: 10.131.63.251.11028 - 10.131.31.251.646State: Oper; Msgs sent/rcvd: 484/487; DownstreamUp time: 06:45:16LDP discovery sources:

Ethernet1/0, Src IP addr: 10.131.31.226Addresses bound to peer LDP Ident:10.131.63.229 10.131.63.221 10.131.63.241 10.131.63.25110.131.31.226

Peer LDP Ident: 10.131.31.252:0; Local LDP Ident 10.131.31.251:0TCP connection: 10.131.31.252.11015 - 10.131.31.251.646

State: Oper; Msgs sent/rcvd: 483/486; DownstreamUp time: 06:45:14LDP discovery sources:Ethernet0/0, Src IP addr: 10.131.31.230

Addresses bound to peer LDP Ident:10.131.31.245 10.131.31.252 10.131.31.230 10.131.31.23310.131.31.237

Check LDP Neighbor Adjacency




Must have

IGP reachability

Must receive

and transmit LDP

#show mpls ldp discoveryLocal LDP Identifier:

10.131.31.252:0Discovery Sources:Interfaces:

Ethernet0/0 (ldp): xmit/recvLDP Id: 10.131.31.251:0


LDP Id: 10.131.63.252:0

ping to router id

Verify routing protocols

Extended Ping to Router ID




Peer LDP Ident: 10.131.63.251

from show mpls ldp neighbor command

Local LDP Ident: 10.131.31.251

from show mpls ldp neighbor command

• #ping• Protocol [ip]:• Target IP address: 10.131.63.251• Repeat count [5]:• Datagram size [100]:

• Timeout in seconds [2]:• Extended commands [n]: y• Source address or interface: loopback 0

• Type of service [0]:• Set DF bit in IP header? [no]:• Validate reply data? [no]:

• Data pattern [0xABCD]:• Loose, Strict, Record, Timestamp, Verbose[none]:• Sweep range of sizes [n]:• Type escape sequence to abort.• Sending 5, 100-byte ICMP Echos to 10.131.63.251, timeout is 2 seconds:• !!!!!

• Success rate is 100 percent (5/5), round-trip min/avg/max = 20/22/32 ms• P2R2#

Verify MPLS Label Binding




•Make sure the routes have labels

#show mpls ip binding10.131.4.0/24in label: imp-null

10.131.31.220/30

in label: 18out label: imp-null lsr: 10.131.31.251:0 inuseout label: 20 lsr: 10.131.63.252:0

#show mpls ip binding 10.131.31.220 3010.131.31.220/30

in label: 18

out label: imp-null lsr: 10.131.31.251:0 inuseout label: 20 lsr: 10.131.63.252:0

#show mpls ldp binding 10.131.31.220 30

tib entry: 10.131.31.220/30, rev 26local binding: tag: 18

remote binding: tsr: 10.131.31.251:0, tag: imp-nullremote binding: tsr: 10.131.63.252:0, tag: 20



Verify MPLS




First see if you are getting labels assigned

• Use these commands to validate MPLS:• show mpls forwarding-table

• show mpls forwarding-table 10.10.10.4 32 detail

• show mpls ldp bindings 10.10.10.4 32

If not, then verify set-up

Verify MPLS Forwarding Table




#show mpls forwarding-tableLocal Outgoing Prefix Bytes tag Outgoing Next Hoptag tag or VC or Tunnel Id switched interface16 Untagged 6.6.6.7/32 0 Se0/1.3 point2point

17 Pop tag 10.1.1.12/30 0 Se0/1.1 point2point18 Pop tag 10.10.10.1/32 0 Se0/1.1 point2point19 Pop tag 10.10.10.6/32 782 Se0/1.3 point2point

20 22 10.10.10.4/32 48 Se0/1.1 point2point21 21 10.10.10.5/32 182 Se0/1.1 point2point22 Pop tag 10.1.1.16/30 0 Se0/1.1 point2point

MPLS Forwarding Table Details




To see MPLS forwarding table details:#show mpls forwarding-table 10.10.10.4 /32 detailLocal Outgoing Prefix Bytes tag Outgoing Next Hoptag tag or VC or Tunnel Id switched interface

20 22 10.10.10.4/32 48 Se0/1.1 point2pointMAC/Encaps=4/8, MTU=1520, Tag Stack{22}

48D18847 00016000

No output feature configured

Per-packet load-sharing, slots: 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Removethis

Verify MPLS Label Bindings




For i nternal use

For LDP use this command#show mpls ldp bindings 10.10.10.4 32

10.10.10.4/32, rev 77local binding: label: 20remote binding: lsr: 10.10.10.1:0, label: 22remote binding: lsr: 10.10.10.6:0, label: 24

For TDP use this command

#show tag-switching tdp bindings 10.10.10.4 32tib entry: 10.10.10.4/32, rev 77

local binding: tag: 20remote binding: tsr: 10.10.10.1:0, tag: 22


Verify Routing Protocol Is Running




For i nternal use

#show ip route 10.10.10.4

Routing entry for 10.10.10.4/32

Known via "ospf 9", distance 110, metric 391, type intra areaRedistributing via ospf 9

Last update from 10.1.1.5 on Serial0/1, 00:05:34 agoRouting Descriptor Blocks:* 10.1.1.5, from 44.44.44.1, 00:05:34 ago, via Serial0/1.1

Route metric is 391, traffic share count is 1





Benefits of MPLS




For i nternal use

De-couples IP packet forwarding from the information carried in

the IP header of the packetProvides multiple routing paradigms (e.g., destination-based,explicit routing, VPN, multicast, CoS, etc…) over a commonforwarding algorithm (label swapping)

Facilitates integration of ATM and IP - from control plane pointof view an MPLS-capable ATM switch looks like a router



Control and Forward Plane Separation




For i nternal use

LFIB

RoutingProcess

MPLS

Process

RIB

LIB

FIB

Route

Updates/

Adjacency

Label Bind

Updates/

Adjacency

IP TrafficMPLS Traffic

Control Plane

Data Plane



RFC 2547: MPLS VPNs




For i nternal use

VRF

VRF

VRF

LDP LDPLDP

iBGP—VPNv4

Label Exchange

iBGP—VPNv4 iBGP—VPNv4

PE

PE

PE

CE

CE

CE

CE

Overlapping Addresses Are

Made Unique by Appending RD

and Creating VPNv4 Addresses

CE

Control Plane Path




For i nternal use

RD—8 byte field—assigned by provider —significant to the provider networkonly

VPNv4 address: RD+VPN prefix

Unique RD per VPN makes the VPNv4 address unique

PEP P

PE

CECE

No Direct Peering Between CEs

Routing Relationship

VPNv4 Routes Advertised via BGP

Labels Exchanged via BGP

VPN A VPN A

IPv4 Route

Exchange



MPLS-Based IP-VPN Architecture




For i nternal use

Scalable VPNs• Add more PEs if more VPNs

are needed

• No N^2 mesh

• VPNs are built in to the cloud

IP QoS and traffic engineering

Easy to manage and no VC meshprovisioning required

Provides a level ofsecurity/separation equivalent toFrame Relay and ATM

Supports the deploymentof new value-added applications

Customer IP address freedom

MPLS Network

Traffic Separation at Layer 3

Each VPN Has Unique RD

MPLS VPN Renault

MPLS VPN Bankcorp

VPN A

Site 2

VPN A

Site 3

Corp A

Site 1

Corp B

Site 2

Corp B

Site 1

Corp B

Site 3

VPN Membership-

Based on Logical Port

Label Stacking




For i nternal use

There may be more than one label in an MPLS packet

As we know labels correspond to forwardingequivalence classes• Example—there can be one label for routing the packet to an egress point and another that

separates a customer A packet from customer B

• Inner labels can be used to designate services/FECs, etc.

– e.g. VPNs, fast reroute

Outer label used to route/switch the MPLSpackets in the network

Last label in the stack is marked with EOS bit

Allows building services such as• MPLS VPNs

• Traffic engineering and fast re-route• VPNs over traffic engineered core

• Any transport over MPLS

TE Label

LDP Label

VPN Label

Inner Label

Outer Label

IP Header



MPLS Links




For i nternal use

Link to MPLS Home Page (CCO):

http://www.cisco.com/warp/public/732/Tech/mpls/MPLS Technical Documents (CCO):

http://www.cisco.com/warp/public/732/Tech/mpls/mpls_techdoc.shtml

Link to Tunnel Builder Home Page:http://www.cisco.com/warp/public/732/Tech/mpls/tb/

Link to MPLS Working Group Page (IETF):

http://www.ietf.org/html.charters/mpls-charter.html

http://www.cisco.com/warp/public/732/Tech/mpls/



http://www.cisco.com/warp/public/732/Tech/mpls/tb/





http://www.cisco.com/warp/public/732/Tech/mpls/tb/



http://www.cisco.com/warp/public/732/Tech/mpls/



Thank You!