ip multicast training - cisco

1© 2001, Cisco Systems, Inc.

IP Multicast OverviewIP Multicast OverviewIP Multicast OverviewIP Multicast Overview

Cisco Advanced ServicesCisco Advanced ServicesCisco Advanced ServicesCisco Advanced Services

2© 2002, Cisco Systems, Inc. IP Multicast Basics

AgendaAgenda

• Part 1 - Basic IP Multicast– Multicast Applications, Network Components,

Addressing, IGMP

– Multicast Routing at a High Level

• Part 2 - Configuration Example

• Part 3 - RP Details– Auto-RP, BSR, Anycast


Part 1 – Basic IP MulticastPart 1 – Basic IP Multicast

• Why IP Multicast?– When sending same data to multiple receivers

– Better bandwidth utilization• Send traffic to where it needs to go

– Less host/router processing

– Receivers’ addresses unknown

– Trade-off is state creation and maintenance

• Challenges with IP Multicast– Configuration is generally easy

– Troubleshooting is relatively more complex• Need to worry about state creation and flags• Concern is where the packet came from versus where the packet

is going in unicast


Multicast ApplicationsMulticast Applications

Corporate BroadcastsCorporate Broadcasts

Distance LearningDistance Learning

TrainingTraining

Video Conferencing

Video Conferencing

Whiteboard/Collaboration

Whiteboard/Collaboration

Multicast File Transfer

Multicast File TransferData and File Replication

Data and File Replication

Real-Time Data Delivery—FinancialReal-Time Data Delivery—Financial

Video-On-Demand

Video-On-Demand

Live TV and Radio Broadcast Live TV and Radio Broadcast to the Desktopto the Desktop


Nature of Multicast ApplicationsNature of Multicast Applications

• Usually UDP based– So, no TCP windowing / slow-start

– WRED does not apply

• Duplicate Delivery– During some transition periods, duplicate packet delivery

can occur

• Reliable Multicast


Interdomain MulticastInterdomain MulticastCampus MulticastCampus Multicast

Multicast Network ComponentsMulticast Network Components

• End Stations (hosts-to-routers):– IGMP

• Switches (Layer 2 Optimization):– CGMP, IGMP Snooping or RGMP

• Routers (Multicast Forwarding Protocol):

– PIM Sparse Mode or Bidirectional PIM

• Multicast routing across domains– MBGP

• Multicast Source Discovery– MSDP with PIM-SM

• Source Specific Multicast– PIM-SSM

ISP B

Multicast SourceY

ISP A

Multicast SourceX

ISP B

DRRP

RP

DRDRIGMP PIM-SM

CGMPMBGP

MSDP

ISP A


GroupMember 2

“Non” GroupMember

Group Member 1

B

E

A D

C

Group Member 3

Multicast Network ComponentsMulticast Network Components

1. If you send to group address, all members receive it

2. You must be a “member” of a group to receive data

3. You do not have to be

a member of a group to send to a group


Multicast Network Components for AT&T’s MVPN Service

Multicast Network Components for AT&T’s MVPN Service

Customer PIM Adjacency

CE

CE

CE

Global Multicast

Customer PIM Adjacency

CustomerPIM Adjacency

VRF

mVRF PE

PE

PE PGlobal

SPs RP

Customer’s RP

Source

Receiver

SP PIM Adjacency


• IP Multicast Group Addresses– 224.0.0.0 – 239.255.255.255– Class “D” Address Space

• High order bits of 1st Octet = “1110”• Reserved Link-local Addresses

– 224.0.0.0 – 224.0.0.255 (used typically by routing protocols)– Transmitted with TTL = 1 (not forwarded by routers)– Examples:

• 224.0.0.1 All systems on this subnet• 224.0.0.2 All routers on this subnet• 224.0.0.9 RIPv2• 224.0.0.5 OSPF routers• 224.0.0.13 ALL PIM ROUTERS

• Other Reserved Addresses – 224.0.1.0 – 224.0.1.255 (forwarded by routers, e.g. Auto-RP)

Multicast Addressing Multicast Addressing


• Administratively Scoped Addresses

– Same as RFC 1918 addresses• 239.0.0.0 – 239.255.255.255

– Used to limit “scope” of multicast traffic

– Configured via “ip multicast boundary…” on an interface• multicast traffic with the group range specified cannot enter or leave the

network

– Example – ABC Inc. with Divisions A and B

• Both A and B use 239.255.0.0/16 range of addresses

• Boundary routers in A and B are configured with these addresses as

administrative boundaries

– A and B reuse the same group addresses but cannot talk to each other

• ABC Inc. uses 239.0.0.0/8 boundary company wide

Multicast Addressing Multicast Addressing


• Can use TTL thresholds on router interfaces to contain multicast forwarding

– S0 is RPF interface

– S1, S2, E0 are in OIL

– S2 and E0 have TTL threshold = 0

– S1 TTL threshold = 100

• Packet will be forwarded on S2 and E0, not S1

– Forward if, current TTL (4) >

configured threshold

– Else, drop.

Side Topic – Using TTL Side Topic – Using TTL

E0

S1

S0

S2

Multicast Packet arrives with

TTL=5


H3

• Host sends IGMP Report to join group

• There are several IGMP versions – 1,2,3

• Useful on routers for testing multicast forwarding

– Specify “ip igmp join-group X” on a loopback interface to

simulate a receiver

H3224.1.1.1

Report

H1 H2

Joining a Group

Receivers Announce Their PresenceReceivers Announce Their Presence


Shortest Path or Source Distribution Tree

Receiver 1

B

E

A D F

Source 1Notation: (S, G) S = Source G = Group

C

Receiver 2

Source 2

Multicast Routing – High LevelMulticast Routing – High Level



Shared Distribution Tree

Receiver 1

B

E

A F

Notation: (*, G) * = All Sources G = Group

C

Receiver 2

(RP) PIM Rendezvous Point

Shared Tree

D (RP)



Shared and Source Trees

Receiver 1

B

E

A F

Source 1 Notation: (*, G) * = All Sources G = Group

C

Receiver 2

Source 2

(RP) PIM Rendezvous Point

Shared Tree

Source Tree

D (RP)



• Source or Shortest Path trees

Uses more memory O(S x G) but you get optimal

paths from source to all receivers; minimizes delay

• Shared trees

Uses less memory O(G) but you may get sub-

optimal paths from source to all receivers; may

introduce extra delay

CharacteristicsCharacteristics of Distribution Trees



• What is RPF?What is RPF?A router forwards a multicast datagram only if received on the up stream interface to the source (i.e. it follows the distribution tree).

• The RPF CheckThe RPF Check• The routing table used for multicasting is checked against the “source” IP address in the packet.

• If the datagram arrived on the interface specified in the routing table for the source address; then the RPF check succeeds.

• Otherwise, the RPF Check fails.

Reverse Path Forwarding (RPF)



Source151.10.3.21

Example: RPF Checking RPF Checking

Mcast Packets

RPF Check FailsRPF Check Fails Packet arrived on wrong interface!Packet arrived on wrong interface!



RPF Check Fails!

Unicast Route TableUnicast Route Table

NetworkNetwork Interface Interface

151.10.0.0/16151.10.0.0/16 S1S1

198.14.32.0/24198.14.32.0/24 S0S0

204.1.16.0/24204.1.16.0/24 E0E0

A closer look: RPF Check Fails RPF Check Fails

Packet Arrived on Wrong Interface!

E0

S1

S0

S2

S1S1

Multicast Packet fromSource 151.10.3.21

XDiscard Packet!



A closer look: RPF Check SucceedsRPF Check Succeeds

RPF Check Succeeds!

Unicast Route TableUnicast Route Table

NetworkNetwork Interface Interface

151.10.0.0/16151.10.0.0/16 S1S1

198.14.32.0/24198.14.32.0/24 S0S0

204.1.16.0/24204.1.16.0/24 E0E0

E0

S1

S0

S2

Multicast Packet fromSource 151.10.3.21

Packet Arrived on Correct Interface!S1S1

Forward out all outgoing interfaces.(i. e. down the distribution tree)



Why do RPF Checks?

E0

S1

S0

S2

• Avoid receiving duplicate packets

• Happens with PIM-DM flooding

• Avoid loops

• Ensures fan-out from source

•multicasting forwarding AWAY from the source

• RPF interface always leads back to the source Non-RPF Interface

RPF Interface



•Dense-mode• Uses “Push” Model

• Traffic Flooded throughout network

• Pruned back where it is unwanted

• Flood & Prune behavior (typically every 3 minutes)

• Sparse-mode

• Uses “Pull” Model

• Traffic sent only to where it is requested

• Explicit Join behavior



• Currently, there are four multicast routing protocols:

– PIM-Dense Mode (Internet-draft)

– PIM-Sparse Mode (RFC 2362- v2)

– PIM-Source Specific Multicast

– Bidirectional PIM

– Others (DVMRP, MOSPF, etc.)

• What “Protocol Independent” means

– Doesn’t care how the unicast routing table has been

built• DVMRP cares – it builds its own !!


Source

Initial Flooding

Receiver

Multicast Packets

(S, G) State created inevery every router in the network!

PIM-DM Flood and PrunePIM-DM Flood and Prune


Source

Pruning Unwanted Traffic

Receiver

Multicast Packets

Prune Messages



Results After Pruning

Source

Receiver

Multicast Packets

Flood and Prune processFlood and Prune processrepeats every 3 minutes!!!repeats every 3 minutes!!!

(S, G) State still exists inevery every router in the network!



PIM-DM — EvaluationPIM-DM — Evaluation

• Most effective for small pilot networks• Advantages:

– Easy to configure—two commands– Simple flood and prune mechanism

• Potential issues...– Inefficient flood and prune behavior– Complex Assert mechanism

– Mixed control and data planes

•Results in (S, G) state in every router in the network

•Can result in non-deterministic topological

behaviors– No support for shared trees


PIM-SM (RFC 2362)PIM-SM (RFC 2362)

• Supports both source and shared trees– Assumes no hosts want multicast traffic unless they

specifically ask for it – PULL MODEL

• Uses a Rendezvous Point (RP)– Senders and Receivers “rendezvous” at this point to learn of

each others existence.

• Senders are “registered” with RP by their first-hop router.

• Receivers are “joined” to the Shared Tree (rooted at the RP) by their local Designated Router (DR).

• Appropriate for…– Wide scale deployment for both densely and sparsely

populated groups in the enterprise– Optimal choice for all production networks regardless of size

and membership density.


PIM-SM Shared Tree JoinPIM-SM Shared Tree Join

Receiver

RP

(*, G) Join

Shared Tree

(*, G) State created onlyalong the Shared Tree.

Router knows IP address of RPIf the last of the receivers behind thisrouter leaves, then its (*.G) OIL is empty (NULL). The router will send (*,G) Prune towards RP.


PIM-SM Sender RegistrationPIM-SM Sender Registration

Receiver

RP

(S, G) Join

Source

Shared Tree

(S, G) Register (unicast)

Source Tree

2. (S, G) State created onlyalong the Source Tree.

3. Source requests RP to build a tree to it1. Source sends multicast data

encapsulated in PIM-SM (S,G) Register to RP - unicast

4. RP sends packet on shared tree

5. RP sends (S,G) Jointowards Source

6. RP now has an SPT to the source

7. RP sends a (S,G) Register-Stop towards Source

8. Traffic flows SPT to RP and Shared Tree to Receiver


PIM-SM SPT SwitchoverPIM-SM SPT Switchover

Receiver

RP

(S, G) Join

Source

Source Tree

Shared Tree1. Last-hop router joins the Source Tree.

2. Additional (S, G) State is created along new part of the Source Tree.

Traffic Flow

3. Router is receiving duplicate packets – SPT and Shared TreeRouter send (S,G) RP-bit Prune toward RP

(S,G) RP-bit Prune

(S,G) Prune4. RP sends (S.G) Prune towards Source


PIM-SM State RefreshPIM-SM State Refresh

Receiver

RP

(*, G) State created onlyalong the Shared Tree.

Receiver

RTR Y sends (*,G) and (S,G) Joins to RTR X every 1 minute

RTR X

RTR Y

RTR X waits for 3 minute Before flushing the interface from the (S,G) or (*,G) OIL

Source


PIM-SM—EvaluationPIM-SM—Evaluation

•Effective for sparse or dense distribution of multicast receivers

•Advantages:

– Traffic only sent down “joined” branches

– Can switch to optimal source-trees for high traffic

sources dynamically

– Unicast routing protocol-independent


PIM SSMPIM SSM

• Assume a One-to-Many Multicast Model.– Example: Video/Audio broadcasts, Stock Market data

• Why does PIM-SM need a Shared Tree?– So that hosts and 1st hop routers can learn who the active

source is for the group.

• What if this was already known?– Hosts could use IGMPv3 to signal exactlyexactly which (S,G) SPT

to join.

– The Shared Tree & RP wouldn’t be necessary.

– Different sources could share the same Group address and not interfere with each other.

• Result: Source Specific Multicast (SSM)


PIM SSMPIM SSM

•SSM Advantages

– Allows immediate use of shortest forwarding

path to a specific source, without need to

create shared tree.

– Eliminates dependence on MSDP for finding

sources.

– Simplifies address allocation for global, single

source groups when combined with

elimination of shared trees.


Receiver 1

Source

Out-of-band Source DirectoryExample: Web Server

Receiver learns of source, group/port

IGMPv3 (S, G) Join

Receiver sends IGMPv3 (S,G) Join

(S, G) Join

First-hop send PIM s,g join directly toward Source

BA C D

FD

PIM Source Specific ModePIM Source Specific Mode


PIM Source Specific ModePIM Source Specific Mode

Receiver 1

B

F

A C D

Source

E

Result: Shortest Path Tree rootedat the Source, with NO Shared Tree.


Rendezvous Point – High LevelRendezvous Point – High Level

• RP is key to the operation of PIM-SM• How do the multicast routers know about the RP?• Three methods are popular

– Static RP• Statically configure the RP address on all multicast routers

• Can have a separate RPs for different groups

– Auto-RP• Routers that want to be RPs announce to Mapping Agents

• Mapping Agents determine RP and inform all routers

• Uses dense mode groups 224.0.1.39 and 224.0.1.40 to achieve this

– BSR• Similar to Auto-RP – Candidate RPs announce their intention

• But Candidate BSRs don’t determine the RPs – they send all the RP

information to all routers and let them decide.


AgendaAgenda


Addressing, IGMP



• Part 3 – RP Details– Auto-RP, BSR, Anycast


Configuration SetupConfiguration Setup

R1

R6

10.0.1/24

192.168.1/3010.0.2/24

PE and P L0 = 12.0.0.N / 32

R9(PE)

1.1.1.1/32

R7

R8-RR

R3 - RR

R2(PE)

R5R4(PE)

s3/0

s2/0

s3/0

s2/0

s2/0

s2/0

e0/0

e0/0

e0/0e1/0

e0/0

s1/0

s1/0

s1/0

e0/0

s4/0

s3/0

s3/0

s3/0

s2/0s1/0

s4/0s2/0

s1/0

5.5.5.5/32

10.0.3/2410.0.4/24

10.0.5/24

10.0.6/2410.0.7/24

10.0.8/24

10.0.9/24

192.168.3/30

192.168.2/30

AS 13979

ip igmp join-group 239.1.1.1

Multiple Loops

pinging 239.1.1.1


Config and Show Commands - 1Config and Show Commands - 1

• All interfaces on PE and P routers are enabled for PIM. For instance, interface Serial1/0 ip address 10.0.1.2 255.255.255.0 ip pim sparse-dense-mode

– including loopback0

• What interfaces are enabled for PIM?– R2#sh ip pim int

Address Interface Ver/ Nbr Query DR DR Mode Count Intvl Prior12.0.0.2 Loopback0 v2/SD 0 30 1 12.0.0.210.0.1.2 Serial1/0 v2/SD 1 30 1 0.0.0.010.0.2.2 Serial2/0 v2/SD 1 30 1 0.0.0.010.7.0.2 Serial4/0 v2/SD 0 30 1 0.0.0.0



• To check PIM on the customer interface

– R2#sh ip pim vrf test1 intAddress Interface Ver/ Nbr Query DR DR Mode Count Intvl Prior

192.168.1.2 Ethernet0/0 v2/SD 1 30 1 192.168.1.2

12.0.0.2 Tunnel0 v2/SD 2 30 1 12.0.0.9

R2#

• To check PIM adjacencyR2#sh ip pim neiPIM Neighbor Table

Neighbor Interface Uptime/Expires Ver DR

Address Priority/Mode

10.0.1.7 Serial1/0 00:26:45/00:01:38 v2 1 /

10.0.2.3 Serial2/0 00:26:45/00:01:43 v2 1 /

R2#~



• To check PIM adjacency on the customer interfaceR2#sh ip pim vrf test1 neiPIM Neighbor TableNeighbor Interface Uptime/Expires Ver DRAddress Priority/Mode192.168.1.1 Ethernet0/0 00:28:37/00:01:42 v2 1 /12.0.0.9 Tunnel0 00:25:27/00:01:24 v2 1 / DR12.0.0.4 Tunnel0 00:28:26/00:01:29 v2 1 /R2#

• Check what is the RP for this groupR2#sh ip pim rp mapPIM Group-to-RP MappingsGroup(s): 224.0.0.0/4, Static RP: 12.0.0.3 (?)R2#

• For customer facing, R2#sh ip pim vrf test1 rp mapPIM Group-to-RP MappingsGroup(s): 224.0.0.0/4, Static RP: 5.5.5.5 (?)R2#



• Is the AT&T RP reachable?R2#ping 12.0.0.3

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 12.0.0.3, timeout is 2 seconds:

!!!!!

• Is the customer RP reachable?R2#ping vrf test1 5.5.5.5


Sending 5, 100-byte ICMP Echos to 5.5.5.5, timeout is 2

seconds:

!!!!!



• Let’s make R2 a receiverR2(config)#int loop0R2(config-if)#ip igmp join-group 239.2.2.2R2#sh ip igmp gIGMP Connected Group MembershipGroup Address Interface Uptime Expires Last Reporter239.1.1.1 Loopback0 02:21:17 stopped 0.0.0.0239.2.2.2 Loopback0 00:01:43 00:02:12 12.0.0.2224.0.1.40 Loopback0 02:21:18 00:02:06 12.0.0.2

• R2 sends *G Join to RP (R3)R2#sh ip mro 239.2.2.2(*, 239.2.2.2), 00:03:50/00:02:08, RP 12.0.0.3, flags: SJCL Incoming interface: Serial2/0, RPF nbr 10.0.2.3 Outgoing interface list: Loopback0, Forward/Sparse-Dense, 00:03:50/00:02:08

• What does the RP (R3) think about 239.2.2.2?R3#sh ip mro 239.2.2.2 (*, 239.2.2.2), 00:14:12/00:02:35, RP 12.0.0.3, flags: S Incoming interface: Null, RPF nbr 0.0.0.0 Outgoing interface list: Serial1/0, Forward/Sparse-Dense, 00:14:12/00:02:35



• Let’s have a source behind R4 send to 239.2.2.2R4#ping 239.2.2.2


Sending 1, 100-byte ICMP Echos to 239.2.2.2, timeout is 2 seconds:

Reply to request 0 from 10.0.2.2, 48 ms



R4#

• Why three responses?

– ping to multicast sends pings on all interfaces

– can control this via extended ping

– response to ping is unicast

• What states do the routers show?



• Look at the state on R4 – first hop router

(*, 239.2.2.2), 00:03:41/stopped, RP 12.0.0.3, flags: SPF

Incoming interface: Serial4/0, RPF nbr 10.0.4.7

Outgoing interface list: Null

(10.0.6.4, 239.2.2.2), 00:03:41/00:00:26, flags: FT

Incoming interface: Serial3/0, RPF nbr 0.0.0.0, Registering

Outgoing interface list:

Serial4/0, Forward/Sparse-Dense, 00:03:41/00:03:24

(12.0.0.4, 239.2.2.2), 00:03:41/00:00:32, flags: FT

Incoming interface: Loopback0, RPF nbr 0.0.0.0, Registering

Outgoing interface list:

Serial4/0, Forward/Sparse-Dense, 00:03:41/00:03:24


Multicast TraceMulticast Trace

R1#mtrace 1.1.1.1 5.5.5.5 ? Hostname or A.B.C.D Group to trace route via <cr>

R1#mtrace 1.1.1.1 5.5.5.5 Type escape sequence to abort.Mtrace from 1.1.1.1 to 5.5.5.5 via RPFFrom source (?) to destination (?)Querying full reverse path... 0 5.5.5.5-1 192.168.3.5 PIM [1.1.1.1/32]-2 0.0.0.0 None Admin. Prohibited !RPF!192.168.3.4 [default]-3 0.0.0.0 PIM [1.1.1.1/32]-4 192.168.1.1 PIM [1.1.1.1/32]R1#


AgendaAgenda


Addressing, IGMP



• Part 3 – RP Details– Auto-RP, BSR, Anycast


Rendezvous Points (RPs)Rendezvous Points (RPs)

• Meeting Place for Source and Receivers

• Last hop routers join the RP

• First hop routers register towards RP– Designated routers send Register Messages towards RP

• RPs can be– Manually configured - Static RPs

– Dynamic via Cisco’s Auto-RP

– Dynamic via BSR

• One RP can support several groups

• A single group cannot have more than one active RP

• If RP is not known, group will become dense


Static RP’sStatic RP’s

• Hard-coded RP address

– When used, must be configured on every router

– All routers must have the same RP address

– RP fail-over not possible (except if Anycast RPs are used)

• Commandip pim rp-address <address> [group-list <acl>] [override]

– Optional group list specifies group range

• Which multicast groups should this RP be used for?

• Default is all – 224.0.0.0/4

– Override keyword “overrides” Auto-RP information

• w/o override - Auto-RP learned info takes precedence


Auto-RP OverviewAuto-RP Overview

• A way to let routers in a PIM domain dynamically learn about active RPs

• Basic Idea– Routers wishing to be RPs for a group(s) multicast a

Candidate RP message

• To group address 224.0.1.39 (Cisco-RP-Announce)

– A Mapping Agent (MA) gets these and selects one

– MA multicasts this RP info to all other routers

• To group address 224.0.1.40 (Cisco-RP-Discovery)

– Routers cache this Group-to-RP mapping

– 224.0.1.39 and 224.0.1.40 operate in dense mode


Auto-RP—From 10,000 FeetAuto-RP—From 10,000 Feet

Announce Announce

An

no

un

ceA

nn

ou

nce

Announce Announce

An

no

un

ceA

nn

ou

nce

Announce

RP-Announcements multicast to theCisco Announce (224.0.1.39) group

AA

CC DDC-RP

1.1.1.1C-RP

2.2.2.2

BB

MA MA


CC DDC-RP

1.1.1.1C-RP

2.2.2.2

Auto-RP—From 10,000 FeetAuto-RP—From 10,000 Feet

Discovery

RP-Discoveries multicast to theCisco Discovery (224.0.1.40) group

MA MADiscovery

Discovery

Dis

cove

ry

Dis

cove

ry

AA

Discovery

Discovery

Dis

cove

ry

Dis

cove

ry

BB


Redundancy via Auto-RPRedundancy via Auto-RP

• Mapping Agent selects an RP with the highest IP address

• More than one candidate RP is announced for a group– If primary fails, then the candidate with next highest

IP address becomes the RP for that group


Sparse-Dense ModeSparse-Dense Mode

• Problem – Chicken & Egg– Mapping agent sends RP announcements to group 224.0.1.40

– Routers need to send joins to Auto-RP group 224.0.1.10 to receive this announcement

– They have to send *G Join to the RP

– But they need to know the RP to be able to that

• Same issue applies to C-RP announcements• Solution – sparse-dense

– Configure interfaces to be sparse-dense

– If RP is known, interface uses sparse-mode

– If RP is not known, interface uses dense mode

• This allows Auto-RP groups to run in dense mode and all other groups in sparse-mode


Auto-RP ConfigurationAuto-RP Configuration

• ip pim send-rp-discovery loopback0 scope 16– Makes this router a mapping agent

– Need to configure pim in the loopback interface

• ip pim send-rp-announce loopback0 scope 16 – Makes this router a Candidate RP

– Scope is a TTL value

• You can specify an ACL with send-rp-announce• ACL specifies group range for which this router is C-

RP


BSR OverviewBSR Overview

• A single Bootstrap Router (BSR) is elected– Multiple Candidate BSR’s (C-BSR) can be configured

• Provides backup in case currently elected BSR fails

– C-RP’s send C-RP announcements to the BSR

• C-RP announcements are sent via unicast

• BSR stores ALL C-RP announcements in the “RP-set”

– BSR periodically sends BSR messages to all routers

• BSR Messages contain entire RP-set and IP address of BSR

• Messages are flooded hop-by-hop throughout the network away from the BSR

– All routers select the RP from the RP-set

• All routers use the same selection algorithm; select same RP


PIMv2 Sparse Mode

PIMv2 Sparse Mode

C-RP C-RP

D

E

F

G

A

BSR—From 10,000 feetBSR—From 10,000 feet

C-RP A

dvertisement

(unicast)

C-RP Advertisement

(unicast)

B C

BSRBSR


PIMv2 Sparse Mode

PIMv2 Sparse Mode

C-RP C-RP

D

E

F

G

A

BSR—From 10,000 feetBSR—From 10,000 feet

BS

R M

sg

s

BSR MsgsBSR Msgs

BS

R M

sg

s

BSR Msgs Flooded Hop-by-Hop

B C

BSRBSR


MSDP ConceptMSDP Concept

•Simple but elegant

– Utilize inter-domain source trees

– Reduces problem to locating

active sources

– RP or receiver last-hop can join

inter-domain source tree


MSDP ConceptsMSDP Concepts

•Works with PIM-SM only– RP’s knows about all sources in a domain

•Sources cause a “PIM Register” to the RP

•Can tell RP’s in other domains of its sources– Via MSDP SA (Source Active) messages

– RP’s know about receivers in a domain•Receivers cause a “(*, G) Join” to the RP

•RP can join the source tree in the peer domain– Via normal PIM (S, G) joins


Domain C

Domain B

Domain D

Domain E

SA

SA

SA SA

SA

SA

Source ActiveMessages

SA

Domain A

SA Message192.1.1.1, 224.2.2.2

SA Message192.1.1.1, 224.2.2.2

r

MSDP Peers

RP

RP

RP

RP

MSDP OverviewMSDP Overview

Join (*, 224.2.2.2)

sRP

Register192.1.1.1, 224.2.2.2

MSDP Example


Domain C

Domain B

Domain D

Domain E

Domain A

RP

RP

RP

RP

r

MSDP Peers

Join

(S

, 224

.2.2

.2)

RP


s

MSDP Example


Domain C

Domain B

Domain D

Domain E

Domain A

RP

RP

RP

RP

r

MSDP Peers

Multicast Traffic RP


s

MSDP Example


Domain C

Domain B

Domain D

Domain E

Domain A

RP

RP

RP

RP

r

MSDP Peers



s

Join

(S, 224.2.2.2)

MSDP Example


Domain C

Domain B

Domain D

Domain E

Domain A

RP

RP

RP

RP

r

MSDP Peers



s

MSDP Example


Anycast RP – OverviewAnycast RP – Overview

•Uses single statically defined RP address– Two or more routers have same RP address

• RP address defined as a Loopback Interface.• Loopback address advertised as a Host route.

– Senders & Receivers Join/Register with closest RP• Closest RP determined from the unicast routing table.

– Can never never fall back to Dense mode.• Because RP is statically defined.

•MSDP session(s) run between all RPs– Informs RPs of sources in other parts of network– RPs join SPT to active sources as necessary



MSDPMSDP

RecRecRecRec RecRecRecRec

SrcSrc SrcSrc

SA SAAA

RP1

10.1.1.1BB

RP2

10.1.1.1

XX



RecRecRecRec RecRecRecRec

SrcSrcSrcSrc

AA

RP1

10.1.1.1BB

RP2

10.1.1.1

XX


Anycast RP ConfigurationAnycast RP Configuration

ip pim rp-address 10.1.1.1 ip pim rp-address 10.1.1.1

Interface loopback 0 ip address 10.0.0.2 255.255.255.255

Interface loopback 1 ip address 10.1.1.1 255.255.255.255!ip msdp peer 10.0.0.1 connect-source loopback 0ip msdp originator-id loopback 0

Interface loopback 0 ip address 10.0.0.1 255.255.255.255

Interface loopback 1 ip address 10.1.1.1 255.255.255.255!ip msdp peer 10.0.0.2 connect-source loopback 0ip msdp originator-id loopback 0

MSDPMSDPBB

RP2

AA

RP1

XX YY


• White Papers

• Web and Mailers

• Cisco Press

CCO Multicast page:http://www.cisco.com/go/ipmulticast

Questions:[email protected]

Customer Support Mailing List: [email protected]

More InformationMore Information

RTFB = “Read the Fine Book”

ip multicast training - cisco

Documents