Controlling Campus Device Access Configuring IP Multicast

Controlling Campus Device Access Configuring IP Multicast
Chapter 10 Chapter 10 Controlling Campus Device Access Purpose: This module describes how to configure network devices to participate in multicast groups. Timing: The total amount of time to complete this chapter: Lesson—1 hour 30 minutes Lab Exercises — 1 hour Note: This section has written exercises at the end. Contents: This section includes the following topics: Objectives Planning for Multicast Configuring Multicast Services Enhancing the Route Processor Enabling CGMP Laboratory Exercise Summary Review Topics Transition: The following are the list of performance objectives that describe what students will be able to do at the end of the course. Configuring IP Multicast © 1999, Cisco Systems, Inc. 10-1

Objectives Upon completion of this chapter, you will be able to perform the following tasks: Configure the primary distribution multilayer switch to forward multicast traffic using the PIM DM protocol Configure the primary distribution multilayer switch to forward multicast traffic using the PIM SM protocol Enable CGMP on the RSM and distribution layer switch Purpose: This graphic states the module objectives. Emphasize: Read or state each objective so each student has a clear understanding of the chapter objectives. At the end of this chapter, the students will be able to: Enable multicast routing on a network Configure an interface with Protocol Independent Multicast (PIM) Configure a candidate rendezvous point (RP) using Auto-RP Configure an RP-mapping agent Enable the Cisco Group Management Protocol (CGMP) on a router and a switch Verify the configuration Transition: The following discusses the Cisco IP multicast support products.

Configuring IP Multicast
In this chapter, we discuss the following topics: Planning for multicast Configuring multicast services Enhancing the route processor Enabling CGMP Purpose: This graphic lists the chapter topics. Emphasize: Read or state each topic so students have a clear understanding of them. Transition: The following is a signpost of the topics covered in the first section.

In this section, we discuss the following topics: Planning for Multicast Configuring IP Multicast Routing Multicast Routing Protocol Types Outgoing Interface Lists Configuring Multicast Services Enhancing the Route Processor Enabling CGMP Purpose: This graphic signposts the topics covered in this section Emphasize: Read or state each topic so each student has a clear understanding of what is covered in this section Transition: The following begins the discussion of planning for IP multicasting.

IP Multicast Application IP Multicast Application
Planning Multicast Server Block Core Block Switch Block Video Servers Distribution Switch Distribution Switch Host Access Switch Core Purpose: This graphic shows the Cisco support multicast products. Emphasize: IP multicast is a Layer 3 protocol, and switches operate at Layer 2. Most switches handle IP multicast traffic by flooding all the ports, which ensures the traffic is received by the requesting workstation. This method wastes bandwidth and network resources on the switch, and other users on the network have less bandwidth available. By employing various multicast protocols within the network, multicast cast devices can forward the IP multicast traffic to only the workstations that requested it. Transition: The following discusses the placement of the protocol within the campus network. IP Multicast Application IP Protocol Stack Supporting Multicast NIC Card IP Multicast Application IP Protocol Stack Supporting Multicast All entities involved must be capable of identifying and supporting multicast traffic

End-to-End IP Multicast
MBONE (DVMRP) Multicast Routing Protocols (PIM) 1 IGMP Core 2 Video Servers CGMP Purpose: This graphic covers the Cisco support multicast products. Emphasize: A functional component of IP multicast is the host-to-router protocols which request admission to or join multicast groups. The Cisco IOS™ software supports the following protocols to implement IP multicast routing: Protocol Independent Multicast (PIM) is used between routers so that they can track which multicast packets to forward to each other and to their directly connected LANs. Internet Group Management Protocol (IGMP) is used between hosts on a LAN and the router(s) on that LAN to track which multicast groups the hosts are members. Cisco Group Management Protocol (CGMP) is a protocol used on routers connected to Cisco Catalyst® switches to perform tasks similar to those performed by IGMP. (Not shown) Distance Vector Multicast Routing Protocol (DVMRP) is the protocol used on the multicast backbone (MBONE) of the Internet. The Cisco IOS software supports PIM-to-DVMRP interaction. This protocol is not shown in the graphic; however, it is important to mention this protocol in terms of connecting to the Internet. Transition: The following discusses how to enable IP multicast routing. 3 IP multicast routing protocols, Protocol Independent Multicast (PIM) Internet Group Management Protocol (IGMP) Cisco Group Management Protocol (CGMP) Channel 1 Channel 2 Channel 3

Enabling IP Multicast Routing
Router>enable Router#show running-config Building configuration... Current configuration: ! hostname Router ip multicast-routing Router(config#ip multicast routing Purpose: This graphic shows the command used to enable IP multicasting on the router. Emphasize: The IP multicast routing tasks are divided into basic and advanced tasks. This next section discusses the basic tasks the students need to accomplish to configure IP multicast in their networks. Cover the following list of tasks: Enabling IP multicast routing Enabling PIM on an interface Configuring the Time To Live (TTL) threshold Configuring a rendezvous point (RP) Joining a multicast group Changing the IGMP version Enabling CGMP This list is not intended to be comprehensive. Router-to-router communications ensures that the network has the appropriate information necessary to forward multicast packets down a multicast distribution tree from source to destination. Transition: The following discusses the various routing protocols. Enabling IP multicast routing allows the Cisco IOS software to forward multicast packets

Dense Mode Floods everywhere initially
Source No Receivers A B D F C E Purpose: This graphic shows the PIM dense mode (PIM DM) protocol. Emphasize: PIM dense mode (Internet draft) uses Reverse Path Forwarding (RPF) to flood the network with multicast data, then prunes back paths based on uninterested receivers. PIM DM periodically refloods the networks to determine changes in multicast group membership. PIM DM interoperates with DVMRP. PIM DM is appropriate for the following: Densely distributed receivers located in close proximity to source Few senders to many receivers (due to frequent flooding) High volume of multicast traffic Constant stream of traffic Transition: The following discusses how entries appear in the oilist. Receiver 1 Receiver 2 Floods everywhere initially Prunes back where no group members Prunes on redundant non-shortest path Induces periodic reflooding

Outgoing Interface Lists (Oilists)
First packet source (*,G) (*, ), 00:29:21/00:02:59, RP , flags: DJC Incoming interface: Null, RPF nbr Outgoing interface list: Vlan42, Forward/Dense, 00:07:01/00:00:00 Vlan43, Forward/Dense, 00:29:07/00:00:00 Vlan45, Forward/Dense, 00:29:07/00:00:00 /32, ), 00:08:06/00:02:59, flags: CT Incoming interface: Vlan45, RPF nbr Vlan42, Forward/Dense, 00:07:02/00:00:00 Vlan43, Forward/Dense, 00:07:02/00:00:00 ( /32, ), 00:15:09/00:02:28, flags: PCT Incoming interface: Vlan42, RPF nbr Outgoing interface list: Null Flood to all interfaces Subsequent packet source (S,G) Flood all MC-enabled interfaces except the incoming interface Purpose: This graphic shows the PIM DM oilist entries. Emphasize: Point out the first packet is address to the (*,G) address with G equal to the destination address of the multicast group. Point out the route processor floods the packet out all multicast enabled interfaces. Point out subsequent packets contain source and destination address. The route processor does not flood the packet out the incoming interface. Transition: The following discusses the PIM spare mode (SM) protocol. Prune Flag VLAN 43 VLAN 45 VLAN 42 Prune Statement

Sparse Mode No one receives group traffic until a specific join
Source 1 Rendezvous Point Non-Viewers A B D F Purpose: This graphic shows the PIM sparse mode protocol Emphasize: Each PIM SM multicast group has an associated RP router. The RP router is the root of the shared tree for the group. When a source system multicasts data to a PIM SM group, its local PIM router encapsulates the data in a registration packet and unicasts it to the RP. The RP decapsulates the packet and forwards it to the known group members. PIM SM uses one shortest path tree per group, and the root of the tree is the RP router. The tree is shared by all sources for the group, so it is called a shared tree. The routing table entries in a shared tree have a wildcard (*) for the source. They are referred to as (*, G) entries. The intended RP router does not need to be specially configured to act as an RP. When a join request packet arrives at a router that is addressed as the RP, that router will assume the role of RP for the group (G) identified in the request. Transition: The following discusses how sparse-mode entries appear in the oilist. C E Receiver 1 Non-Viewer No one receives group traffic until a specific join Rendezvous point queried Sites pruned back permanently as needed No periodic flooding as in dense-mode

Sparse Mode Join Flag Set
Sparse Mode Oilist Sparse Mode Join Flag Set RP IP Address (*,G) Entry (*, ), 3d03h/00:02:59, RP , flags: SJC Incoming interface: null, RPF nbr Outgoing interface list: FastEthernet0/0, Forward/Sparse, 1d21h/00:02:13 ( , ), 00:02:55/00:00:04, flags: PCT Incoming interface: FastEthernet0/0, RPF nbr Outgoing interface list: Null Incoming Interface Outgoing Interfaces Purpose: This graphic shows the PIM sparse mode oilist entries. Emphasize: The Incoming interface is Null and the RPF nbr is This indicates that this router is the RP. Both a (*, G) and (S, G) entry was created as a result of receiving the first multicast packet from source S for group G. (Note: It is not possible to have an (S, G) entry without an (*, G) entry in a Cisco router.) 1d21h/00:02:13 indicates that the entry has existed for 5 seconds and will expire in 2 minutes and 54 seconds. The S flag indicates that this is a sparse-mode group. The J flag indicates that this group has joined the short-path tree. The C flag indicates that directly connected hosts (C) exists. The P flag (pruned) is also set since the oilist is Null. The T flag is set indicating that traffic is flowing down the shortest-path tree. FastEthernet0/0, Forward/Sparse, 1d21h/00:02:13 indicates FastEthernet 0/0 is in the oilist, in the Forward state, Sparse mode, and that it has been in the list for 1 day, 21 hours, and will expire in 2 minutes and 13 seconds. Transition: The following discussion PIM Dense-SM protocol. Indicates this router Is the RP Prune Flag Is Set FA 0/0 Source Group G

In this section, we discuss the following topics: Planning for Multicast Configuring Multicast Services Configuring a PIM Interface Choosing and displaying a PIM neighbor Configuring a Rendezvous Point Defining the scope of delivery Enhancing the Route Processor Enabling CGMP Purpose: This graphic signposts the topics covered in this section Emphasize: Read or state each topic so each student has a clear understanding of what is covered in this section Transition: The following begins the discussion of configuring IP multicasting.

Configuring a PIM interface
Router>enable Router#show running-config hostname Router ! ip multicast-routing (text deleted) interface Vlan101 ip address ip pim sparse-dense-mode Router(config)#interface vlan41 Router(config-if)#ip pim sparse-dense Purpose: This graphic shows the command used to configure a PIM interface. Emphasize: An interface can be configured to be in dense mode, sparse mode, or sparse-dense mode. The mode determines how the router populates its multicast routing table and how the router forwards multicast packets received from directly connected LANs. To enable PIM on an interface, enter the ip pim mode command in interface configuration mode. Modes are as follows: Dense mode enables dense mode of operation. Dense mode is used when all routers in the network will need to distribute multicast traffic for each multicast group. Sparse mode enables sparse mode of operation. Sparse mode is used when relatively few routers in the network will be involved in each multicast. Sparse-dense mode enables the interface to act in the mode in which the group operates. In sparse-dense mode, the interface is treated as dense mode if no rendezvous point is detected; the interface is treated as sparse mode if a rendezvous point is detected. To disable PIM on the interface, enter the no ip pim command. Transition: The following completes the discussion of configuring the PIM protocol. The multicast routing protocol must be specifically assigned to an interface

Verifying the PIM Interface Configuration
RSM144#show ip pim interface Address Interface Mode Nbr Query DR Count Intvl Vlan Sparse-Dense Vlan Sparse-Dense Vlan Sparse-Dense Vlan Sparse-Dense Vlan Sparse-Dense Vlan Sparse-Dense Vlan Sparse-Dense Purpose: This graphic shows the command used to verify the PIM configuration on the interface. Emphasize: To display information about interfaces configured for PIM, enter the show ip pim interface command in EXEC mode. The following variable are available: type indicates the type of interface. This variable is optional. number indicates the number of the interface. This variable is optional. count displays the number of packets received and sent out the interface. The show ip pim interface command displays information for all PIM- configured virtual LANs (VLANs) on the device when a specific type and number is not specified. The show ip pim interface command displays information about interfaces configured for PIM

Verifying the PIM Interface Configuration (text only)
The results of this command display the following items: IP address of the next-hop router. The interface type. On an RSM, this value will be the VLAN designation. The PIM mode configured on each interface. Number of PIM neighbors that have been discovered through this interface. Frequency, in seconds, of PIM router-query messages. IP address of the designated router on the LAN. Transition: The following covers designated routers.

Selecting a Designated Router
PIM Router 1 PIM Router 2 Highest IP Address Elected as DR PIM Query PIM Query Purpose: This graphic shows how designated routers are chosen. Emphasize: Cisco routers use the PIM routing protocol to forward multicast traffic. Two PIM routers are neighbors if there is a direct connection between them. PIM neighbor discovery occurs as follows: PIM queries are sent periodically to discover the existence of other PIM routers on the network. For multiaccess networks (for example, Ethernet), the PIM query message is multicast to the all-routers ( ) multicast group address. Designated router (DR) election is as follows: To elect the DR, each PIM node on a multiaccess network examines the received PIM query messages from its neighbors and compares the IP address of its interface with the IP address of its PIM neighbors. The PIM neighbor with the highest IP address is elected the DR. If no PIM queries have been received from the elected DR after some period of configurable time, the DR election mechanism is run again to elect a new DR. Transition: The following continues the discussion of designated routers. PIM queries are multicast to the all-routers ( ) multicast group address periodically (Default = 30 seconds) If the DR times-out, a new DR is elected

Selecting a Designated Router (cont.)
PIM Router Designated Router Host Query Host Reply Purpose: This graphic continues the discussion on designated routers. Emphasize: Only one router sends a query message. All PIM-enabled routers receive the host replies. Transition: The following discusses the command used to view PIM neighbors. Only the designated router sends host query messages on a LAN All PIM routers on a single subnet receive replies from the host

Displaying the PIM Neighbor Table
RSM145>show ip pim neighbor PIM Neighbor Table Neighbor Address Interface Uptime Expires Mode FastEthernet1/0 2d02h :01:08 v1 Sparse-Dense FastEthernet1/0 3d01h :01:24 v1 Sparse-Dense (DR) FastEthernet1/0 3d01h :01:02 v1 Sparse-Dense FastEthernet1/0 3d01h :01:19 v1 Sparse-Dense FastEthernet2/0 2d02h :01:08 v1 Sparse-Dense FastEthernet2/0 3d01h :01:24 v1 Sparse-Dense (DR) FastEthernet2/0 3d01h :01:02 v1 Sparse-Dense FastEthernet2/0 3d01h :01:19 v1 Sparse-Dense Purpose: This graphic shows the show ip pim neighbor command. Emphasize: Each multicast-enabled router is configured to know which interfaces will be using PIM. These interfaces either connect to neighboring PIM routers in the network or to host systems on a LAN. If there are multiple PIM routers on a LAN, they are considered to be neighbors. The show ip pim neighbor command is used to display information about the PIM neighbor table in the router. Command output is as follows: Neighbor Address—The IP address of the PIM neighbor. Interface—the interface where the PIM query of this neighbor was received. Uptime—The period of time that this PIM neighbor has been active. Expires—The period of time after which this PIM neighbor will no longer be considered as active. (Reset by the receipt of another PIM query.) Mode—PIM mode (sparse, dense or sparse/dense) that the PIM neighbor is using. (DR)—Indicates that this PIM neighbor is the designated router for the network. Transition: The following discusses multicast rendezvous points in the network. The PIM neighbor table can be used to display the neighboring routers for a specific router

Configuring a Rendezvous Point
Router144#show run hostname Router (text deleted) ! ip classless ip pim rp-address IPTV Server Leaf Router Router144(config)#ip pim rp-address Rendezvous Point Purpose: This graphic shows the command used to configure a rendezvous point. Emphasize: The IP address of the rendezvous points must be configured on leaf routers. The leaf routers send PIM register messages on behalf of a host sending a packet to the group. The last-hop routers use the RP address to send PIM join or prune messages to the RP to inform it about group membership. To designate the RP address on a leaf router, enter the ip pim rp-address command in global configuration mode. The command contains the following fields: ip-address—Designates the IP address of a router to be a PIM RP. group-access-list-number—Specifies a number of an access list that defines for which multicast groups the RP should be used. This is a standard IP access list. The number can be from 1 to 100. override option—Indicates that if there is a conflict between the RP configured with this command and one learned by auto-RP, the RP configured with this command prevails. Transition: The following introduces auto-RP. Campus Network Leaf Router

Auto-RP Campus Network Router B Router A RP Mapping Agent Designated
I would like to be the RP for Group XYZ. Router A is the RP for Group ABC and Router B is is the RP for Group XYZ. I would like to be the RP for Group ABC. Router B Router A RP Mapping Agent Campus Network Purpose: This graphic introduces the concept of auto-RP. Emphasize: Auto-RP is a Cisco proprietary standalone protocol that automates the distribution of group-to-RP mappings in a network running sparse-mode PIM. Auto-RP facilitates the use of multiple RPs within a network to serve different group ranges. Auto-RP also allows load splitting among different RPs and arrangement of RPs according to the locations of group participants. Sequence is as follows: 1. The RP announce must be entered on the router to act as an RP for a certain range of multicast group addresses. 2. An RP mapping agent is assigned to a router to receive the RP announcement messages. 3. The RP mapping agent then sends the consistent group-to-RP mappings to all designated routers. If all interfaces are in sparse mode, a default RP must be configured to support the two well-known groups and Transition: The following continues the discussion of auto-RP. Designated Router Designated Router Designated Router

Configuring send rp-announce
Router#show running-config hostname Router ! ip multicast-routing (text deleted) ip pim rp-address ip pim send-rp-announce vlan101 scope 16 Router(config)#ip pim send-rp-announce vlan101 scope 16 Purpose: This graphic shows how to configure a candidate RP. Emphasize: The RP announce command is entered on the router/RSM. This command announces the router as a candidate RP to act as a rendezvous point for a certain range of multicast group addresses. Multiple RPs can be used to serve different group ranges. Auto-RP is disabled by default. To enable auto-RP on a router, enter the ip pim send-rp-announce command in global configuration mode. The command contains the following fields: type indicates the type of interface for the RP address. number indicates the number of the interface for the RP address. TTL indicates the time-to-live value that limits the scope of the announcements. access-list-number indicates the access list that describes the group ranges for which this router is the RP. To change the group range for an RP, change the announcement setting on the RP. If the change is valid, all other routers will automatically pick up the new group-RP mapping. Transition: The following continues the discussion of auto-RP. Auto-RP requires an RP announce command on the router

Auto-RP Discovery RP Candidate RP Candidate Well-Known Group
rp-announce Message rp-announce Message Well-Known Group RP Mapping Agent rp-discovery Message rp-discovery Message Purpose: This graphic introduces the concept of auto-RP mapping agents. Emphasize: Candidate RPs send an auto-RP announcement message to the well- known group CISCO-RP-ANNOUNCE ( ). A router configured as an RP mapping agent listens on this well-known group address CISCO-RP-ANNOUNCE ( ) to determine which RPs act for the various ranges of multicast group addresses. The RP mapping agent then sends the RP-to-group mappings in an auto-RP discovery message to the well-known group CISCO-RP-DISCOVERY ( ). PIM DRs listen to the well-known group CISCO-RP-DISCOVERY ( ) to determine which RPs to use. By default, a router is not configured as a PIM RP mapping agent. The RP mapping agent should be configured on the same router as the RP. Transition: The following continues the discussion of auto-RP. Well-Known Group Well-Known Group Designated Router Designated Router Designated Router Designated Router Designated Router Designated Router

Configuring send rp-discovery
Router#show running-config hostname Router ! ip multicast-routing (text deleted) ip pim rp-address ip pim send-rp-discovery scope 16 Router(config)#ip pim send-rp-discovery scope 16 Purpose: This graphic shows the auto-RP mapping agent command. Emphasize: The ip pim send-rp-discovery scope command enables a router to send RP discovery messages and is entered in global configuration mode. Transition: The following discusses how to configure the scope of delivery. A router must be explicitly configured as a mapping agent

Configuring ttl-threshold
interface Vlan101 ip address ip pim sparse-dense-mode ip multicast ttl-threshold 16 Router(config)#interface vlan101 Router(config-if)#ip multicast ttl-threshold 16 Purpose: This graphic introduces the ttl-threshold command. Emphasize: Only multicast packets with a TTL greater than the interface TTL threshold are forwarded on the interface. Packets with a TTL equal to or less than the interface threshold are discarded. The default value for the TTL threshold on an interface is zero (0). All multicast packets are forwarded on the interface with a TTL of zero. The ip multicast ttl-threshold command changes the default TTL threshold value. To restore the default value of zero (0), enter the no ip multicast ttl-threshold command in interface configuration mode. Transition: The following discusses the multicast routing table. Only multicast packets with a TTL greater than the interface TTL threshold are forwarded on the interface

Displaying the Multicast Routing Table
Host Entry RSM114#show ip mroute IP Multicast Routing Table Flags: D - Dense, S - Sparse, C - Connected, L - Local, P - Pruned R - RP-bit set, F - Register flag, T - SPT-bit set, J - Join SPT Timers: Uptime/Expires Interface state: Interface, Next-Hop or VCD, State/Mode (*, ), 00:30:17/00:02:59, RP , flags: SP Incoming interface: Vlan52, RPF nbr Outgoing interface list: Null ( /32, ), 00:01:49/00:01:10, flags: PT (*, ), 00:29:22/00:02:59, RP , flags: SJP Incoming interface: Null, RPF nbr Purpose: This graphic shows the multicast routing table. Emphasize: Each PIM SM multicast group has an associated RP router. The RP router is the root of the shared tree for the group. When a source system multicasts data to a PIM SM group, its local PIM router encapsulates the data in a registration packet and unicasts it to the RP. The RP decapsulates the packet and forwards it to the known group members. PIM SM uses one shortest path tree per group, and the root of the tree is the RP router. The routing table entries in a shared tree have a wildcard (*) for the source. They are referred to as (*,G) entries. The intended RP router does not need to be specially configured to act as an RP. When a join request packet arrives at a router that is addressed as the RP, that router will assume the role of RP for the group (G) identified in the request. Source Entry

Displaying the Multicast Routing Table (Text Only)
The definition of the fields in this display are as follows: Flags: Provides information about the entry. D Dense Entry is operating in dense mode. S Sparse Entry is operating in sparse mode. C Connected A member of the multicast group is present on the directly connected interface. L Local The router itself is a member of the multicast group. P Pruned Route has been pruned. The Cisco IOS software keeps this information in case a downstream member wants to join the source. R Rp-bit set Indicates that the (S,G) entry is pointing towards the RP. This is typically a prune state along the shared tree for a particular source. F Register flag indicates that the software is registering for a multicast source. T SPT-bit set indicates that packets have been received on the shortest path source tree. (*, ) ( /32, ) These addresses signify entries in the IP multicast routing table. The entry consists of the IP address of the source router, followed by IP address of the multicast group. An asterisk (*) in place of the source router indicates all sources. Entries in the first format are referred to as (*,G,) or “star comma G,” entries. Entries in the second format are referred to as (S,G) or “S comma G” entries. The (*,G) entries are used to build (S,G) entries. Uptime is the number of hours, minutes, and seconds the entry has been in the IP multicast routing table. Expires indicates how long in hours, minutes, and seconds until the entry will be removed from the IP multicast routing table on the outgoing interface. RP signifies the address of the rendezvous point (RP) router. For routers and access servers operating in sparse mode, this address is always Flags display information about the entry. See the definition of symbols earlier in this section. Incoming interface indicates the expected interface for a multicast packet from the source. If the packet is not received on this interface, it is discarded.

Displaying the Multicast Routing Table (Text Only)
RPF neighbor identifies the IP address of the upstream router to the source. “Tunneling” indicates that this router is sending data to the RP encapsulated in register packets. The hexadecimal number in parentheses indicates the RP to which we are registering. Each bit indicates a different RP if multiple RPs per group are used. Dvmrp or Mroute indicates if the RPF information is obtained from the DVMRP routing table or the static mroutes configuration. Outgoing interface list identifies the interfaces through which packets will be forwarded. VLAN101 is the name and number of the outgoing interface. Forward/Dense indicates that packets will be forwarded on the interface if there are no restrictions due to access lists or TTL threshold. The following the slash is the mode in which the interface is operating (dense or sparse). The timestamp specifies how long in hours, minutes, and seconds the entry has been in the IP multicast routing table. The following the slash, the timestamp indicates how long in hours, minutes, and seconds until the entry will be removed from the IP multicast routing table. Transition: The following introduces how to log IP packets.

Logging Multicast Packets
Router#debug ip mpacket IP multicast packets debugging is on RSM114# 3d06h : IP: s= (Vlan51) d= len 60, mforward 3d06h : IP: s= (Vlan52) d= len 60, mforward 3d06h : IP: s= (Vlan51) d= len 65, mforward 3d06h : IP: s= (Vlan52) d= len 65, mforward Purpose: This graphic shows the results of the debug ip mpacket command. Emphasize: This command displays information for multicast IP packets that are forwarded from a specific router. You can limit the display to multicast packets from specific sources by using an access list. This graphic uses the group argument to limit the display to packets destined for multicast group The graphic describes the output fields in the entry. Transition: The following is the signpost of the next section. Action Taken on the Packet Bytes in the Packet Multicast group address Receiving Interface Address of the Packet Source

In this section, we discuss the following topics: Planning for Multicast Configuring Multicast Services Enhancing the Route Processor Joining a multicast group Manipulating the IGMP version Enabling CGMP Purpose: This graphic signposts the topics covered in this section Emphasize: Read or state each topic so each student has a clear understanding of what is covered in this section Transition: The following discusses how to make a router a member of a multicast group.

Joining a Multicast Group
I am a member of Group I will answer that ping. Router#ping Type escape sequence to abort. Sending 1, 100-byte ICMP Echos to , timeout is 2 seconds: Reply to request 0 from , 1 ms IP Address of the Interface Servicing the Group Campus Network Purpose: This graphics shows a router joining a multicast group. Emphasize: If all the multicast-capable routers and access servers that you administer are members of a multicast group, pinging that group causes all routers to respond. Point out that in this example, the router belongs to three multicast groups as follows: Well-known group CISCO-RP-ANNOUNCE ( ) Well-known group CISCO-RP-DISCOVERY ( ) Multicast group Because the ip igmp join-group command is entered in interface configuration command mode, the router responds to the ping command with the IP address of the interface that services that IP multicast group. Transition: The following starts the discussion of the differences between IGMP Version 1 and 2. RSM144#show ip igmp int vlan41 Vlan41 is up, line protocol is up Internet address is /24 IGMP is enabled on interface Current IGMP version is 2 (text deleted) Multicast designated router (DR) is (this system) IGMP querying router is Multicast groups joined: List of Group Memberships

IGMPv2 and IGMPv1 Devices in the Same Subnet
IGMPv1 Host IGMPv1 Host IGMPv2 Host H1 H2 H3 Leave to IGMPv1 Router I am configured as a IGMPv1 Router. I will ignore any IGMPv2 leave messages. Purpose: This graphic shows compatibility issues when IGMPv1 and IGMPv2 devices reside on the same subnet. Emphasize: An IGMPv2 host may be placed on a subnet where the querier router has not yet been upgraded to IGMPv2. However, the IGMPv1 router expects Version 1 membership reports in response to its queries, and will not pay attention to Version 2 membership reports. An IGMPv2 router may be placed on a subnet where at least one router on the subnet has not yet been upgraded to IGMPv2. However, the querier MUST use IGMPv1. An IGMPv2 router may be placed on a subnet where there are hosts that have not yet been upgraded to IGMPv2. If there are Version 1 hosts present for a particular group, the IGMPv2 router will ignore any leave group messages that it receives for that group. For more information on IGMPv1 and IGMPv2 compatibility, refer to RFC 2236. Transition: The following discusses the show ip igmp interface command. Mixed-environment routers do not automatically detect the IGMP version of systems on the subnet and dynamically switch between versions

Determining the IGMP Version
Router#show ip igmp interface Vlan101 is up, line protocol is up Internet address is , subnet mask is IGMP is enabled on interface Current IGMP version is 2 CGMP is enabled 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 16 Multicast designated router (DR) is IGMP querying router is (this system) Multicast groups joined: Purpose: This graphic shows the show ip igmp interface command. Emphasize: To determine the current IGMP version of the router, enter the show ip igmp interface command in EXEC privileged mode. Also point out the other useful information provided in the display, such as the following: TTL threshold for a specific interface IP address of the designated router for this router interface Querying router for the subnet this interface services Multicast groups serviced by this interface Transition: The following describes how to change the IGMP version.

Changing the IGMP Version
Router(config-if)#ip igmp version 1 interface Vlan41 ip address ip pim sparse-dense-mode ip multicast ttl-threshold 16 ip igmp version 1 Purpose: This graphic shows how to change the IGMP version on a router. Emphasize: Initially Cisco used to effect an IGMP version change dynamically. However, this method would not guarantee IGMPv2 functionality as the software always defaulted to compatibility mode. RFC 2236 states you should “administratively assure” that the querier is IGMP Version 1. Therefore, if you are mixing IGMP Version 1 and IGMP Version 2, you need to enter the ip igmp version 1 command in interface configuration mode. Transition: The following is the signpost for the next section. The IGMP version has a default of 2

In this section, we discuss the following topics: Planning for Multicast Configuring Multicast Services Enhancing the Route Processor Enabling CGMP Enabling CGMP on the router Enabling CGMP on the switch Enable CGMP Leave Purpose: This graphic signposts the topics covered in this section Emphasize: Read or state each topic so each student has a clear understanding of what is covered in this section Transition: The following begins the discussion of CGMP.

Enabling CGMP on the Router
Router(config-if)#ip cgmp Campus Network Router#show run (text deleted) interface Vlan41 mac-address ip address no ip redirects ip pim sparse-mode ip cgmp Purpose: This graphic shows how to enable CGMP on the router. Emphasize: CGMP allows Catalyst® switches to leverage IGMP information on Cisco routers to make Layer 2 forwarding decisions. With CGMP, IP multicast traffic is delivered only to those Catalyst switch ports that are interested in the traffic. CGMP filtering requires a network connection from the switch to a router running CGMP. CGMP can only run on an interface if PIM is configured on the same interface. Enable CGMP on the router in the interface configuration mode. When CGMP is disabled on a router, a CGMP leave message for group is sent with the router’s MAC address on the interface. Transition: The following continues the discussion of CGMP. CGMP is disabled by default MP can only run on an interface if PIM is configured on the same interface

CGMP — Joining a Group 0100.0cdd.dddd 0100.0cdd.dddd
CGMP Join MAC Address 0000.0c to 0100.0cdd.dddd 0100.0cdd.dddd I can reach device 000.0c out of Port 2. I will add that port to group in my switch forwarding table. To I have no knowledge of device 0000.0c Purpose: This graphic shows of how CGMP works between the switch and the router. Emphasize: CGMP is transparent to end hosts. A CGMP-capable IP multicast router detects all IGMP packets and informs the switch when specific hosts join or leave IP multicast groups. When the CGMP-capable router receives an IGMP control packet, the router creates a CGMP packet that contains the request type, the multicast group address, and the actual MAC address of the host. The router then sends the CGMP packet to a well-known address to which all Catalyst series switches listen. Multicast addresses or port assignments are automatically entered into the Catalyst switch CAM table via the CGMP protocol from the router. The initial report is sent to the all-router multicast address, which contains the desired group and the MAC address of the client. The router builds a CGMP join message and multicasts it to a well-known address (0100.0cdd.dddd) to which all switches listen. All switches receive the packet and search their forwarding tables for that particular MAC address. If the MAC address is resident on one of their local nontrunking ports, the switch creates a multicast forwarding entry in the forwarding table. Transition: The following discusses how to configure CGMP on a switch. 0000.0c I am c I would like to join multicast group

Enabling CGMP on the Switch
Switch (enable) show config (text deleted) #cgmp set cgmp enable set cgmp leave disable Switch (enable)set cgmp enable Purpose: This graphic shows how to enter the set cgmp enable command on a switch. Emphasize: The set cgmp enable command is entered at the EXEC privileged prompt on the switch. The only variables in this command are enable and disable. You can view whether CGMP is enabled by issuing the show config command. Transition: The following continues the discussion of CGMP. By default, CGMP is disabled on the switch

CGMP — Leaving a Group CGMP Remove MAC Address 0000.0c from I can reach device 0000.0c out of Port 2. I will remove that port from group in my switch forwarding table. 0100.0cdd.dddd 0100.0cdd.dddd IGMP Leave to I have no knowledge of device 0000.0c Purpose: This graphic shows the cgmp leave command. Emphasize: For IGMPv1 hosts, the routers query to determine if there are any active hosts within a group. If there are active hosts, the router will do nothing. If, after a number of queries, no reports are heard from any hosts within the group, the router will send a CGMP remove group message to the switch as part of group pruning. IGMPv2 hosts issue a specific leave message to the all-router group for groups the hosts want to leave. The switch forwards the host leave message to the router. If the router detects that no more hosts reside in that multicast group serviced by that interface, the router will send a CGMP remove group message to the switch. The switch, in turn, prunes that port from the distribution tree. Transition: The following continues the discussion of CGMP. 0000.0c If router detects no members left in a multicast group, it sends a CGMP remove to all switches

Enabling CGMP Leave on the Switch
(text deleted) ! #cgmp set cgmp enable set cgmp leave enable Switch (enable) set cgmp leave enable CGMP leave processing enabled. Purpose: This graphic shows the set cgmp leave enable command. Emphasize: CGMP fast-leave-processing allows the switch to detect IGMPv2 leave messages. When the switch receives a leave message, the switch starts a query-response timer. If this timer expires before a CGMP join message is received, the port is pruned from the multicast tree for the multicast group specified in the original leave message. To enable the CGMP leave function on the switch, enter the set cgmp leave command in privileged EXEC mode. The show cgmp leave command provides verification that CGMP fast-leave has been configured. This command can be entered in either user or privileged EXEC mode. To disable the CGMP fast-leave function, enter the set cgmp leave disable command. Transition: The following completes the discussion of CGMP. CGMP leave is disabled by default

Verifying CGMP on the Switch
Switch (enable) show cgmp statistics 41 CGMP enabled CGMP statistics for vlan 41: valid rx pkts received invalid rx pkts received valid cgmp joins received valid cgmp leaves received valid igmp leaves received valid igmp queries received igmp gs queries transmitted igmp leaves transmitted failures to add DSW144 to RTR144 0 topology notifications received 80 number of CGMP packets dropped Purpose: This graphic shows several commands used to collect CGMP information about the switch. Emphasize: Several commands are available to help you verify the CGMP configuration on the switch. These commands allow you to view the relationships between VLANs, CGMP-enabled routers, and switch ports. Refer to the “Configuring Multicast Services” section of the Catalyst 5000 Series Software Configuration Guide (4.3) for a complete list of these commands. The following two commands are useful in helping you verify the CGMP configuration on the switch. The show cgmp statistics VLAN command displays the ongoing CGMP activity for a designated VLAN. The show multicast group cgmp VLAN command displays only the multicast router information that has been learned automatically through CGMP. The results of this command show the multicast group MAC addresses associated with a specific VLAN and the ports associated with those groups. Transition: The following are the laboratory exercises. CGMP statistics display only the information that has been learned automatically through CGMP

Laboratory Exercise: Visual Objective
Multicast Group Member Multicast Group Member Multicast Stream Group Purpose: This graphic shows what the students will accomplish in the lab. Transition: The following is the chapter summary. Multicast Stream Group

Summary Cisco multicast switches and routers support the PIM, IGMP, CGMP, and DVMRP protocols. The DR is responsible for maintaining a current status of group membership on a LAN. The mode in which an interface is configured determines how the routing table is populated and packets are forwarded. The presence or absence of an RP determines how a sparse-dense mode interface will react Auto-RP facilitates the use of multiple RP in a network CGMP leverages IGMP information to make Layer 2 forwarding decisions. Purpose: This page summarize what was discussed in this chapter. Transition: The following are the review questions.

Review Discuss the basic tasks required to set up a multicast session within the network. Describe the three PIM modes. Explain how Auto-RP automates the distribution of group-to-RP mappings in a network. Discuss how CGMP leverages IGMP information to facilitate Layer 2 forwarding decisions. Purpose: This page provides several topics for discussion. Emphasize: Points of Discussion for Review Question 1: The first two basic tasks in the list are required to configure IP multicast routing; the remaining tasks are optional. Enable IP multicast routing This step is essential and must be completed first. If IP multicast routing is not enabled, you cannot configure PIM on an interface on that router. If you attempt to configure a PIM interface prior to completing this step, the router will return the following error message: WARNING: "ip multicast-routing" is not configured, IP Multicast packets will not be forwarded Configure PIM on an interface Two PIM routers are neighbors if there is a direct connection between them. On a multi accessed LAN, one router is selected to poll the LAN for host group membership. The router selected to poll the LAN is called the designated router (DR). The PIM router with the highest IP address becomes the DR for the LAN.

Review (Text only) Routers forward multicast data on a per-interface basis. Therefore, the multicast routing protocol must be specifically assigned to an interface. An interface can be configured to be in PIM dense mode, sparse mode, or sparse-dense mode. Configure a rendezvous point If you configure PIM to operate in sparse mode, you must also choose one or more routers to act as rendezvous points. Rendezvous points are used by senders to a multicast group to announce their existence, and by receivers of multicast packets to learn about new senders. The IP address of the rendezvous points must be configured on leaf routers. The ip pim rp-address ip-address command adds the IP address of the RP on a leaf router. Configure the TTL threshold The ip multicast ttl-threshold command defines the scope or range of multicast delivery. Multicast packets with a TTL greater than the interface TTL threshold are forwarded on the interface. Packets with a TTL equal to or less than the interface threshold are discarded. Join a multicast group Cisco routers can be configured to be members of a multicast group. Being a member of a multicast group is useful in determining multicast reachability in a network. If a router is configured to be a member of a specific multicast group, that router can respond to commands, such as ping and ICMP echo requests, addressed to that group. A group member router can also participate in multicast Cisco IOS trace route actions. Change the IGMP version Cisco routers do not automatically detect the IGMP version of systems on the subnet and dynamically switch between versions. If some hosts on the subnet only support IGMPv1, then the designated router must be configured for IGMPv1. However, once the router is statically configured for IGMPv1, the router will ignore any IGMPv2 leave group messages that the router receives from any IGMPv2 hosts on the same subnet.

Review (Text only) Points of Discussion for Review Question 2:
In dense mode, a router assumes that all other routers want to forward multicast packets for a group. In sparse mode, a router assumes that other routers do not want to forward multicast packets for a group unless there is an explicit request for the traffic. In sparse-dense mode, the interface is treated as dense mode if no rendezvous point is detected; the interface is treated as sparse mode if a rendezvous point is detected. Points of Discussion for Review Question 3: Auto-RP is a Cisco proprietary standalone protocol that automates the distribution of group-to-RP mappings in a network running sparse mode PIM. The ip pim send-rp-announce command announces the router as a candidate RP to act as a rendezvous point for a certain range of multicast group addresses. The RP announce message is sent to CISCO-RP-ANNOUNCE ( ). The ip pim send-rp-discovery command identifies the router as an RP mapping agent. The RP mapping agent sends the RP-to-group mappings in an auto-RP discovery message to the well-known group. PIM DRs listen to the well-known group to determine which RPs to use. These mappings are sent to CISCO-RP-DISCOVERY ( ). Points of Discussion for Review Question 4: When the host wants to receive a multicast stream, the host sends an IGMP join message indicating the group in which the host would like to be a member. The next-hop router receives the IGMP join message, records the source MAC address of the IGMP message, and issues a CGMP join message downstream to all switches. The downstream switches use the CGMP message to dynamically build an entry in the switching table that maps the multicast traffic to the switch port of the client. Using this method, multicast packets will be delivered only to those switch ports that are in the switching table, sparing other ports and attached hosts that do not want to receive those packets. Transition: This concludes the chapter on multicast configuration.

Review (Text only)

Controlling Campus Device Access Configuring IP Multicast

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