© 2006 Cisco Systems, Inc. All rights reserved.Cisco Public BSCI Module 7 Lesson 1 1 BSCI Module 7 Lesson 1 IP Multicasting: Explaining Multicast
Jan 11, 2016
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 1
BSCI Module 7 Lesson 1
IP Multicasting: Explaining Multicast
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 2
Objectives
Describe the IP multicast group.
Compare and contrast Unicast packets and multicast packets.
List the advantages and disadvantages of multicast traffic.
Discuss two types of multicast applications.
Describe the types of IP multicast addresses.
Describe how receivers can learn about a scheduled multicast session.
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 3
Multicast Overview
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 4
IP Multicast
Distribute information to large audiences over an IP network
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 5
Why Multicast?
Used when sending same data to multiple receivers
Better bandwidth utilization
Less host/router processing
Used when addresses of receivers unknown
Used when simultaneous delivery for a group of receivers is required (simulcast)
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 6
Unicast vs. Multicast
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 7
Multicast AdvantagesEnhanced efficiency: Controls network traffic and reduces server and CPU loads
Optimized performance: Eliminates traffic redundancy
Distributed applications: Makes multipoint applications possible
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 8
Types of Multicast Applications
One-to-many
A single host sending to two or more (n) receivers
Many-to-many
Any number of hosts sending to the same multicast group; hosts are also members of the group (sender = receiver)
Many-to-one
Any number of receivers sending data back to a source (via unicast or multicast)
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 9
Corporate Broadcasts
Distance Learning
Training
Videoconferencing
Whiteboard/Collaboration
Multicast File TransferData and File Replication
Real-Time Data Delivery—FinancialVideo-on-Demand
Live TV and Radio Broadcast to the Desktop
IP Multicast Applications
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 10
Self Check
1. List some advantages of multicast transmission over unicast transmission.
2. How does the best effort delivery nature of UDP impact multicast transmissions?
3. What are the 3 basic types of multicast applications?
4. Give examples of one-to-many.
5. What model is used when a host can be a sender as well as a receiver simultaneously?
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 11
Multicast Addressing
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 12
IP Multicast Address Structure
IP group addresses:
Class D address (high-order three bits are set)
Range from 224.0.0.0 through 239.255.255.255
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 13
Multicast Addressing
IPv4 Header
Options Padding
Time to Live Protocol Header Checksum
Identification Flags Fragment Offset
Version IHL Type of Service Total Length
Source Address
Destination AddressDestination
Source
Source Address can never be
Source Address can never be
Class D Multicast Group Address
Class D Multicast Group Address
224.0.0.0 - 239.255.255.255 (Class D) Multicast Group Address RangeDestination
1.0.0.0 - 223.255.255.255 (Class A, B, C)Source
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 14
IP Multicast Address Groups
Local scope addresses224.0.0.0 to 224.0.0.255
Global scope addresses224.0.1.0 to 238.255.255.255
Administratively scoped addresses (private)239.0.0.0 to 239.255.255.255
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 15
Local Scope Addresses
Well-known addresses assigned by IANA
Reserved use: 224.0.0.0 through 224.0.0.255224.0.0.1 (all multicast clients on subnet)
224.0.0.2 (all routers on subnet)
224.0.0.4 (all DVMRP routers)
224.0.0.13 (all PIMv2 routers)
224.0.0.5, 224.0.0.6, 224.0.0.9, and 224.0.0.10 used by unicast routing protocols
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 16
IANA Ethernet MAC Address Range
01-00-5e-00-00-00
through
01-00-5e-7f-ff-ff
Available range of MAC addresses for IP multicast
Because the 7th hexadecimal character is 0 – 7, the 25th bitwill always be 0.
00000001:00000000:01011110:00000000:00000000:00000000
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 17
00000001:00000000:01011110:00000000:00000000:00000000
IANA Ethernet MAC Address Range
through
Within this range, these MAC addresses have the first 25 bits in common.
The remaining 23 bits are available for mapping to the lower 23 bits of the IP multicast group address.
Available range of MAC addresses for IP multicast
00000001:00000000:01011110:01111111:11111111:11111111
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 18
Multicast IP Address to MAC Address
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 19
224.1.1.1224.129.1.1225.1.1.1225.129.1.1 . . .238.1.1.1238.129.1.1239.1.1.1239.129.1.1
0x0100.5E01.0101
1 - Multicast MAC Address(FDDI and Ethernet)
Multicast AddressingSince the only 23 bits of the multicast IP address are usedand the first four bits are always 1110, bits 5 – 8 (five bits)are always ignored!
This means that there are 32 IP addresses that match any onemulticast MAC address!!!
Since the only 23 bits of the multicast IP address are usedand the first four bits are always 1110, bits 5 – 8 (five bits)are always ignored!
This means that there are 32 IP addresses that match any onemulticast MAC address!!!
11100000.00000001.00000001.00000001 = 224.1.1.1
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 20
32 IP Address to 1 Multicast MAC Address
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 21
Summary
IP multicast is a much more efficient means of delivering content where a single sender needs to deliver the content to multiple receivers. This task may be achieved through the use of multicast groups.
IP multicasts are designated by the use of a specific Class D IP address range. This is achieved through global scope addresses, which are assigned dynamically, and administratively scoped, which are assigned locally and are reserved for use inside private domains.
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 22
Resources
Wikipedia IP Multicast articlehttp://en.wikipedia.org/wiki/IP_Multicast
Webopedia Mbone articlehttp://www.webopedia.com/TERM/M/Mbone.html
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 23
BSCI Module 7 Lesson 2
IP Multicasting: IGMP and Layer 2 Issues
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 24
Objectives
Explain the operations of IGMPv2 and how IGMPv2 utilizes Join Group and Leave Group messages.
Explain the operations of IGMPv3 and how IGMPv2 and IGMPv3 interoperate.
Describe the methods used to deal with multicast in a Layer 2 switching environment.
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 25
IGMP Overview
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 26
Internet Group Management Protocol (IGMP)
How hosts tell routers about group membership
Routers solicit group membership from directly connected hosts
RFC 1112 specifies IGMPv1
Supported on Windows 95
RFC 2236 specifies IGMPv2
Supported on latest service pack for Windows and most UNIX systems
RFC 3376 specifies IGMPv3
Supported in Window XP and various UNIX systems
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 27
IGMPv2RFC 2236
Group-specific queryRouter sends query membership message to a single group rather than all hosts (reduces traffic).
Leave group messageHost sends leave message if it leaves the group and is the last member (reduces leave latency in comparison to v1).
Query-interval response timeThe Query router sets the maximum Query-Response time (controls burstiness and fine-tunes leave latencies).
Querier election processIGMPv2 routers can elect the Query Router without relying on the multicast routing protocol.
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 28
IGMPv3
IGMPv3 adds the ability to filter multicasts based on the multicast source.
IGMPv3 allows hosts to indicate that they want to receive traffic only from particular sources within a multicast group.
IGMPv3 is the industry-designated standard protocol for hosts to signal channel subscriptions in Source Specific Multicast (SSM).
http://www.cisco.com/en/US/products/sw/iosswrel/ps1834/products_feature_guide09186a0080080515.html
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 29
IGMPv3 (cont.)
IGMPv3 runs in two modes: INCLUDE and EXCLUDE
INCLUDE mode—In this mode, the receiver announces membership to a host group and provides a list of IP addresses (the INCLUDE list) from which it wants to receive traffic.
EXCLUDE mode—In this mode, the receiver announces membership to a host group and provides a list of IP addresses (the EXCLUDE list) from which it does not want to receive traffic.
This indicates that the host wants to receive traffic only from other sources whose IP addresses are not listed in the EXCLUDE list.
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 30
IGMPv2—Joining a Group
224.1.1.1
Join Group
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 31
IGMPv2—Leaving a Group
IGMPv2 has explicit Leave Group messages, which reduces overall leave latency.
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 32
IGMPv2—Leaving a Group (Cont.)
Hosts H2 and H3 are members of group 224.1.1.1.
1. H2 sends a leave message.
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 33
IGMPv2—Leaving a Group (Cont.)
2. Router sends group-specific query.
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 34
IGMPv2—Leaving a Group (Cont.)
3. A remaining member host sends report, so group remains active.
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 35
IGMPv2—Leaving a Group (Cont.)
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 36
IGMPv2—Leaving a Group (Cont.)
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 37
IGMPv3—Joining a Group
Joining member sends IGMPv3 report to 224.0.0.22 immediately upon joining.
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 38
IGMPv3—Joining Specific Source(s)
IGMPv3 Report contains desired sources in the Include list. Only “Included” sources are joined.
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 39
IGMPv3—Maintaining State
Router sends periodic queries: All IGMPv3 members respond.
Reports contain multiple group state records.
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 40
Self Check
1. What is the primary purpose of IGMP?
2. When 2 IGMP routers are located on the same Ethernet segment, which router will be the designated querier?
3. What does the ICMPv2 Query router doe when it receives a Leave Message?
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 41
IGMP Layer 2 Issues
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 42
Determining IGMP Version Running
Determining which IGMP version is running on an interface.
rtr-a>show ip igmp interface e0Ethernet0 is up, line protocol is up Internet address is 1.1.1.1, subnet mask is 255.255.255.0 IGMP is enabled on interface Current IGMP version is 2 CGMP is disabled on interface IGMP query interval is 60 seconds IGMP querier timeout is 120 seconds IGMP max query response time is 10 seconds Inbound IGMP access group is not set Multicast routing is enabled on interface Multicast TTL threshold is 0 Multicast designated router (DR) is 1.1.1.1 (this system) IGMP querying router is 1.1.1.1 (this system) Multicast groups joined: 224.0.1.40 224.2.127.254
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 43
Layer 2 Multicast Frame Switching
Problem: Layer 2 flooding of multicast frames
Typical Layer 2 switches treat multicast traffic as unknown or broadcast and must flood the frame to every port (in VLAN).
Static entries may sometimes be set to specify which ports receive which groups of multicast traffic.
Dynamic configuration of these entries may reduce administration.
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 44
Layer 2 Multicast Switching Solutions
Cisco Group Management Protocol (CGMP): Simple, proprietary; routers and switches
IGMP snooping: Complex, standardized, proprietary implementations; switches only
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 45
Layer 2 Multicast Frame Switching CGMPSolution 1: CGMP
Runs on switches and routers.
CGMP packets sent by routers to switches at the CGMP multicast MAC address of 0100.0cdd.dddd.
CGMP packet contains:Type field: join or leave
MAC address of the IGMP client
Multicast MAC address of the group
Switch uses CGMP packet information to add or remove an entry for a particular multicast MAC address.
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 46
IGMP SnoopingSolution 2: IGMP snooping
Switches become IGMP-aware.
IGMP packets are intercepted by the CPU or by special hardware ASICs.
Switch examines contents of IGMP messages to learn which ports want what traffic.
Effect on switch without Layer 3-aware Hardware/ASICs
Must process all Layer 2 multicast packets
Administration load increased with multicast traffic load
Effect on switch with Layer 3-aware Hardware/ASICs
Maintain high-throughput performance but cost of switch increases
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 47
Self Check
1. What command is used to determine the version of IGMP active on an interface?
2. How does a typical layer 2 switch treat multicast traffic?
3. What is CGMP?
4. What type of switch is recommending for use with IGMP snooping?
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 48
Summary IGMPv2 is a protocol used by multicast clients to join a
multicast group.
IGMPv3 allows a receiver to specify a source.
If controls such as CGMP and IGMP snooping are not added at the Ethernet switching level, all multicast frames are flooded.
CGMP is a Cisco proprietary protocol used to implement multicast efficiently.
IGMP snooping is a standard protocol that has a function similar to CGMP.
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 49
Resources
Wikipedia IGMP articlehttp://en.wikipedia.org/wiki/IGMP
Multicast in a Campus Network: CGMP and IGMP Snooping
http://www.cisco.com/warp/public/473/22.html
IP Multicast Glossary of Termshttp://www.cisco.com/en/US/tech/tk828/tech_brief0900aecd801bca26.html
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 50
BSCI Module 7 Lesson 3
IP Multicasting: Multicast Routing Protocols
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 51
Objectives
Describe a multicast network in terms of the IP multicast routing protocols and processes used over various segments.
Describe multicast distribution trees including source trees and shared trees.
Describe the (S,G) and (*,G) multicast distribution trees entry formats.
Explain IP multicast routing.
Identify the characteristics of each of the PIM modes.
Describe the operation of PIM-DM, PIM-SM, and PIM sparse-dense modes.
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 52
Multicast Distribution Trees
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 53
Multicast Protocol Basics
Types of multicast distribution trees:
Source distribution trees; also called shortest path trees (SPTs)
Shared distribution trees; rooted at a meeting point in the network
A core router serves as a rendezvous point (RP)
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 54
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 Distribution Trees
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 55
Receiver 1
B
E
A D F
Source 1Notation: (S, G) S = Source G = Group
C
Receiver 2
Source 2
Multicast Distribution TreesShortest Path or Source Distribution Tree
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 56
Multicast Distribution Trees
Receiver 1
B
E
A D F
Notation: (*, G) * = All Sources G = Group
C
Receiver 2
(RP) PIM Rendezvous Point
Shared Tree
(RP)
Shared Distribution Tree
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 57
Multicast Distribution 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)
Shared Distribution Tree
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 58
Multicast Distribution Tree Identification
(S,G) entries – Source Distribution Trees
For this particular source sending to this particular group
Traffic is forwarded through the shortest path from the source
(*,G) entries – Shared Trees
For any (*) source sending to this group
Traffic is forwarded through a meeting point for this group
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 59
Multicast Distribution Trees
CharacteristicsCharacteristics of Distribution Trees
Source or Shortest Path trees
Uses more memory but optimal paths from source to all receivers; minimizes delay
Shared trees
Uses less memory but sub-optimal paths from source to all receivers; may introduce extra delay
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 60
Self Check
1. What is an advantage of Shortest Path Trees compared to Shared Trees?
2. What does multicast use to make it’s forwarding decisions?
3. In the STP notation (S,G), what do each of the characters represent?
4. What is the root of the shared tree called?
5. Compare Shared Distribution trees and SPT trees in terms of router memory and packet delivery delay.
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 61
Multicast Routing
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 62
Protocols for IP Multicast Routing
PIM is used between routers so that they can track which multicast packets to forward to each other and to their directly connected LANs.
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 63
Protocol-Independent Multicast (PIM) PIM maintains the current IP multicast service mode of
receiver-initiated membership.
PIM is not dependent on a specific unicast routing protocol.
With PIM, routers maintain forwarding tables to forward multicast datagrams.
PIM can operate in dense mode or sparse mode.Dense mode protocols flood multicast traffic to all parts of the network and prune the flows where there are no receivers using a periodic flood-and-prune mechanism.
Sparse mode protocols use an explicit join mechanism where distribution trees are built on demand by explicit tree join messages sent by routers that have directly connected receivers.
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 64
Multicast Tree Creation
PIM Join/Prune Control Messages
Used to create/remove Distribution Trees
Shortest Path trees
PIM control messages are sent toward the Source
Shared trees
PIM control messages are sent toward RP
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 65
Multicast Forwarding
Multicast routing operation is the opposite of unicast routing.
Unicast routing is concerned with where the packet is going.
Multicast routing is concerned with where the packet comes from.
Multicast routing uses Reverse Path Forwarding (RPF) to prevent forwarding loops.
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 66
Reverse Path Forwarding (RPF)
The RPF Calculation
The multicast source address is checked against the unicast routing table.
This determines the interface and upstream router in the direction of the source to which PIM Joins are sent.
This interface becomes the “Incoming” or RPF interface.
A router forwards a multicast datagram only if received on the RPF interface.
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 67
Reverse Path Forwarding (RPF)
RPF Calculation
Based on Source Address.
Best path to source found in Unicast Route Table.
Determines where to send Joins.
Joins continue towards Source to build multicast tree.
Multicast data flows down tree.
10.1.1.1
E1
E2
Unicast Route TableNetwork Interface10.1.0.0/24 E0
Join
Join
E0
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 68
Reverse Path Forwarding (RPF)
10.1.1.1
E1E0
E2
Join
Join
RPF Calculation (cont.)
Repeat for other receivers…
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 69
Reverse Path Forwarding (RPF)
RPF Calculation
What if we have equal-cost paths?We can’t use both.
Tie-BreakerUse highest Next-Hop IP address.
10.1.1.1
E1E0
E2 Unicast Route TableNetwork Intfc Nxt-Hop10.1.0.0/24 E0 1.1.1.110.1.0.0/24 E1 1.1.2.1
1.1.2.11.1.1.1Join
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 70
Self Check
1. Why is Protocol Independent Multicast called Independent?
2. Describe dense mode operation.
3. What does multicast routing use to prevent forwarding loops?
4. What is the RPF interface?
5. What if the RFP calculation finds 2 equal-cost paths?
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 71
PIM Dense Mode Operation
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 72
PIM-DM Flood and Prune
Initial Flooding
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 73
PIM-DM Flood and Prune (Cont.)
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 74
PIM-DM Flood and Prune (Cont.)
Results After Pruning
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 75
Self Check
1. What happens to packets arriving through the non-RPF interface?
2. When would prune messages be sent on the RPF interface?
3. How often do prune messages expire in PIM-DM?
4. What happens when the prune messages expire?
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 76
PIM Sparse Mode Operation
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 77
PIM Sparse Mode
PIM-SM works with any of the underlying unicast routing protocols.
PIM-SM supports both source and shared trees.
PIM-SM is based on an explicit pull model.
PIM-SM uses an RP.Senders and receivers “meet each other.”
Senders are registered with RP by their first-hop router.
Receivers are joined to the shared tree (rooted at the RP) by their local DR.
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 78
PIM-SM Shared Tree Join
Receiver
RP
(*, G) Join
Shared Tree
(*, G) State created onlyalong the Shared Tree.
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 79
PIM-SM Sender Registration
Receiver
RP
(S, G) Join
Source
Shared Tree
(S, G) Register (unicast)
Source Tree
(S, G) State created onlyalong the Source Tree.Traffic Flow
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 80
PIM-SM Sender Registration
Receiver
RPSource
Shared Tree
Source Tree RP sends a Register-Stop back to the first-hop router to stop the Register process.
(S, G) Register-Stop (unicast)
Traffic Flow
(S, G) Register (unicast)
(S, G) traffic begins arriving at the RP through the Source tree.
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 81
PIM-SM Sender Registration
Receiver
RPSource
Shared Tree
Source Tree
Traffic FlowSource traffic flows nativelyalong SPT to RP.
From RP, traffic flows downthe Shared Tree to Receivers.
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 82
PIM-SM SPT Switchover
Receiver
RP
(S, G) Join
Source
Source Tree
Shared Tree
Last-hop router joins the Source Tree.
Additional (S, G) State is created along new part of the Source Tree.
Traffic Flow
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 83
PIM-SM SPT Switchover
Receiver
RPSource
Source Tree
Shared Tree
(S, G)RP-bit Prune
Traffic begins flowing down the new branch of the Source Tree.
Additional (S, G) State is created along along the Shared Tree to prune off (S, G) traffic.
Traffic Flow
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 84
PIM-SM SPT Switchover
Receiver
RPSource
Source Tree
Shared Tree
(S, G) Traffic flow is now pruned off of the Shared Tree and is flowing to the Receiver through the Source Tree.
Traffic Flow
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 85
PIM-SM SPT Switchover
Receiver
RPSource
Source Tree
Shared Tree
(S, G) traffic flow is no longer needed by the RP so it Prunes the flow of (S, G) traffic.
Traffic Flow
(S, G) Prune
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 86
PIM-SM SPT Switchover
Receiver
RPSource
Source Tree
Shared Tree
(S, G) Traffic flow is now only flowing to the Receiver through a single branch of the Source Tree.
Traffic Flow
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 87
“The default behavior of PIM-SM is that routers with directly connected members will join the Shortest Path Tree as soon as they detect a new multicast source.”
PIM-SM Frequently Forgotten Fact
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 88
Multiple RPs with Auto RP
PIM Sparse-Dense-Mode
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 89
Self Check
1. What types of deployments is PIM-SM appropriate for?
2. When using PIM-SM, to what device does the receiver send a Join when wishing to receive multicast traffic?
3. How is a Register message used?
4. Explain the implications of the default value of the SPT-Threshold in Cisco routers.
5. Describe the potential issues with PIM-SM.
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 90
Summary IP multicast requires multiple protocols and processes for proper packet
forwarding.
Source and shared trees may be used to define multicast packet flows to group members.
Multicast routing utilizes the distribution trees for proper packet forwarding.
PIM is the routing protocol for multicast.
PIM-DM uses flood and prune.
PIM-SM uses less device and bandwidth resources and is typically chosen to implement multicast.
PIM sparse-dense mode is the recommended methodology for maximum efficiency in IP multicast.
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 91
Q and A
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 92
Resources
Internet Protocol IP Multicast Technologyhttp://www.cisco.com/en/US/tech/tk828/tech_brief09186a00800a4415.html
IP Multicast Deployment Fundamentalshttp://www.cisco.com/en/US/tech/tk828/tech_brief09186a00800e9952.html
Cisco IOS Multicast Q&Ahttp://www.cisco.com/en/US/tech/tk828/technologies_q_and_a_item09186a00801bb25d.shtml
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 93
BSCI Module 7 Lesson 4
IP Multicasting: Multicast Configuration and Verification
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 94
Objectives
Enable PIM Sparse Mode and Sparse-Dense Mode on a router interface.
Verify the multicast routing table.
Determine if PIM neighbors are correctly configured.
Verify RP information and the IGMP group state.
Configure a router as a statically connected member.
Verify IGMP snooping.
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 95
Multicast Configuration
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 96
Enabling IP Multicast Routing
ip multicast-routing
router(config)#
Enables multicast routing. Enabling IP multicast routing allows the Cisco IOS
software to forward multicast packets.
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 97
Enabling PIM on an Interface
ip pim { sparse-mode | sparse-dense-mode }
router(config-if)#
Enables PIM SM on an interface; the sparse-dense-mode option enables mixed sparse-dense groups.
Enabling PIM on an interface also enables IGMP operation on that interface.
Recommended method is to use sparse-dense-mode option.
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 98
Announcing the RP and the Group Range It Serves
ip pim send-rp-announce {interface type} scope {ttl} group-list {acl}
router(config)#
Configures a router to be the RP for the local group as defined in the access list.
The following example advertises the IP address of Ethernet 0 as the RP for the administratively scoped groups:
ip pim send-rp-announce ethernet0 scope 16 group-list 1access-list 1 permit 239.0.0.0 0.255.255.255
router(config)#
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 99
Assigning the RP Mapping Agent
ip pim send-rp-discovery {interface type} scope {ttl}
router(config)#
The RP mapping agent is the router that tells other routers which group-to-RP range to use.
Such a role is necessary in the event of conflicts (such as overlapping group-to-RP ranges).
Find a router whose connectivity is not likely to be interrupted and assign it the role of RP-mapping agent.
All routers within ttl number of hops from the source router receive the Auto-RP Discovery messages.
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 100
Self Check
1. What is the purpose if the ip multicast-routing command?
2. How is IGMP enabled on an interface?
3. What is the recommended method for configuring an interface for PIM-SM operation?
4. What is the potential issue when configuring an interface for sparse mode or dense mode, rather than sparse-dense?
5. What is the RP mapping agent?
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 101
Verifying Multicast Configuration
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 102
Inspecting Multicast Routing Table
Displays the contents of the IP multicast routing tablesummary: Displays a one-line, abbreviated summary of each entry in the IP multicast routing table.
count: Displays statistics about the group and source, including number of packets, packets per second, average packet size, and bits per second.
active: Displays the rate at which active sources are sending to multicast groups. Active sources are those sending at a rate specified in the kbps argument or higher. The kbps argument defaults to 4 kbps.
show ip mroute [group-address] [summary] [count] [active kbps]
router#
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 103
show ip mroute
NA-1#sh ip mrouteIP Multicast Routing TableFlags: D - Dense, S - Sparse, B - Bidir Group, s - SSM Group, C - Connected L - Local, P - Pruned, R - RP-bit set, F - Register flag, T - SPT-bit set, J - Join SPT, M - MSDP created entry, X - Proxy Join Timer Running, A - Advertised via MSDP, U - URD, I - Received Source Specific Host ReportOutgoing interface flags: H - Hardware switchedTimers: Uptime/ExpiresInterface state: Interface, Next-Hop or VCD, State/Mode
(*, 224.1.1.1), 00:07:54/00:02:59, RP 10.127.0.7, flags: S Incoming interface: Null, RPF nbr 0.0.0.0 Outgoing interface list: Serial1/3, Forward/Sparse, 00:07:54/00:02:32
(172.16.8.1, 224.1.1.1), 00:01:29/00:02:08, flags: TA Incoming interface: Serial1/4, RPF nbr 10.139.16.130 Outgoing interface list: Serial1/3, Forward/Sparse, 00:00:57/00:02:02
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 104
Finding PIM Neighbors
show ip pim interface [type number] [count]
router#
Displays information about interfaces configured for PIM
show ip pim neighbor [type number]
router#
Lists the PIM neighbors discovered by the router
mrinfo [hostname | address]
router#
Queries which neighboring multicast routers are peering with the local router or router specified
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 105
show ip pim interface
NA-2#show ip pim interfaceAddress Interface Ver/ Nbr Query DR DR Mode Count Intvl Prior10.139.16.133 Serial0/0 v2/S 1 30 1 0.0.0.010.127.0.170 Serial1/2 v2/S 1 30 1 0.0.0.010.127.0.242 Serial1/3 v2/S 1 30 1 0.0.0.0
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 106
show ip pim neighbor
NA-2#show ip pim neighborPIM Neighbor TableNeighbor Interface Uptime/Expires Ver DRAddress Priority10.139.16.134 Serial0/0 00:01:46/00:01:28 v2 None10.127.0.169 Serial1/2 00:01:05/00:01:40 v2 1 (BD)10.127.0.241 Serial1/3 00:01:56/00:01:18 v2 1 (BD)
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 107
Checking RP Information
Displays active RPs that are cached with associated multicast routing entries.
Mapping—displays all group-to-RP mappings that the router is aware of
show ip pim rp [group-name | group-address | mapping]
router(config)#
Displays how IP multicast routing does Reverse Path Forwarding (RPF).
Source Address—source address of the host for which RPF information is displayed
Name—name of the host for which RPF information is displayed
show ip rpf {source address | name }
router(config)#
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 108
show ip pim rp
P4-2#show ip pim rpGroup: 224.1.2.3, RP: 10.127.0.7, uptime 00:00:20, expires never
P4-2#show ip pim rp mappingPIM Group-to-RP Mappings
Group(s) 224.0.1.39/32 RP 10.127.0.7 (NA-1), v1 Info source: local, via Auto-RP Uptime: 00:00:21, expires: neverGroup(s) 224.0.1.40/32 RP 10.127.0.7 (NA-1), v1 Info source: local, via Auto-RP Uptime: 00:00:21, expires: neverGroup(s): 224.0.0.0/4, Static RP: 10.127.0.7 (NA-1)
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 109
show ip rpf
(towards the RP)NA-2#show ip rpf 10.127.0.7RPF information for NA-1 (10.127.0.7) RPF interface: Serial1/3 RPF neighbor: ? (10.127.0.241) RPF route/mask: 10.127.0.7/32 RPF type: unicast (ospf 1) RPF recursion count: 0 Doing distance-preferred lookups across tables
(towards the source)NA-2#show ip rpf 10.139.17.126RPF information for ? (10.139.17.126) RPF interface: Serial0/0 RPF neighbor: ? (10.139.16.134) RPF route/mask: 10.139.17.0/25 RPF type: unicast (ospf 1) RPF recursion count: 0 Doing distance-preferred lookups across tables
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 110
Checking the Group State
show ip igmp interface [type number]
router#
Displays multicast-related information about an interface
show ip igmp groups [group-address | type number]
router#
Displays the multicast groups that are directly connected to the router and that were learned via IGMP
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 111
Configure a Router as a Group Member
ip igmp join-group group address
Router (config-if)#
Configure a router to join a specific multicast group and enable IGMP on an interface.
ip igmp static-group group-address
Router (config-if)#
Configures the router as a statically connected member of a group
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 112
show ip igmp interface
rtr-a>show ip igmp interface e0Ethernet0 is up, line protocol is up Internet address is 1.1.1.1, subnet mask is 255.255.255.0 IGMP is enabled on interface Current IGMP version is 2 CGMP is disabled on interface IGMP query interval is 60 seconds IGMP querier timeout is 120 seconds IGMP max query response time is 10 seconds Inbound IGMP access group is not set Multicast routing is enabled on interface Multicast TTL threshold is 0 Multicast designated router (DR) is 1.1.1.1 (this system) IGMP querying router is 1.1.1.1 (this system) Multicast groups joined: 224.0.1.40 224.2.127.254
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 113
show ip igmp groups
rtr-a>sh ip igmp groupsIGMP Connected Group MembershipGroup Address Interface Uptime Expires Last Reporter224.1.1.1 Ethernet0 6d17h 00:01:47 1.1.1.12224.0.1.40 Ethernet0 6d17h never 1.1.1.17
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 114
Verifying IGMP Snooping on a Switch
Displays information about multicast groups.
If igmp keyword is used, only IGMP-learned information is shown.
show multicast group [igmp] [mac_addr] [vlan_id]
switch>
Displays information on dynamically learned and manually configured multicast router ports.
If igmp keyword is used, only IGMP-learned information is shown.
show multicast router [igmp] [mod_num/port_num] [vlan_id]
switch>
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 115
Verifying IGMP Snooping—Example
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 116
Switch> show igmp statistics 10IGMP enabled
IGMP statistics for vlan 10:
IGMP statistics for vlan 10: Transmit: General Queries: 0 Group Specific Queries: 0 Reports: 0 Leaves: 0
Receive: General Queries: 1 Group Specific Queries: 0 Reports: 2 Leaves: 0 Total Valid pkts: 4 Total Invalid pkts: 0 Other pkts: 1 MAC-Based General Queries: 0 Failures to add GDA to EARL: 0 Topology Notifications: 0
Verifying IGMP Snooping—Example (Cont.)
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 117
Switch> show multicast router igmpPort Vlan---------- ---------------- 4/1 10
Total Number of Entries = 1'*' - Configured'+' - RGMP-capable
Switch> show multicast group igmp
VLAN Dest MAC/Route Des [CoS] Destination Ports or VCs / [Protocol Type]---- ---------------------------------------------------------------------10 01-00-5e-00-01-28 4/110 01-00-5e-01-02-03 4/1-2
Total Number of Entries = 2
Verifying IGMP Snooping—Example (Cont.)
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 118
Self Check
1. What command can be used to view the multicast routing table?
2. What commands can be used with PIM-SM to check PIM-enabled interfaces?
3. Why should the show ip pim rp mapping command be used instead of the show ip pim rp command?
4. Why might you configure a router to be a multicast group member?
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 119
Summary
Configuring a simple multicast network requires a global multicast command, a multicast command for each interface, and the specification of an RP discovery method.
Effective methods for verifying a multicast network include checking the multicast routing table and checking PIM neighbors.
Configuring IGMP snooping on an Ethernet switch avoids the problem of multicast frame flooding.
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 120
Q and A
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 121
Resources
Cisco IOS IP Multicast Configuration Guidehttp://cisco.com/en/US/partner/products/ps6350/products_configuration_guide_book09186a0080435b9f.html
IP Multicast Deployment Fundamentalshttp://cisco.com/en/US/partner/tech/tk828/tech_brief09186a00800e9952.html
Multicast Quick-Start Configuration Guidehttp://cisco.com/en/US/partner/tech/tk828/technologies_tech_note09186a0080094821.shtml
Basic Multicast Troubleshooting Toolshttp://cisco.com/en/US/partner/tech/tk828/technologies_tech_note09186a0080093f21.shtml
© 2006 Cisco Systems, Inc. All rights reserved. Cisco PublicBSCI Module 7 Lesson 1 122