The documentation set for this product strives to use bias-free language. For the purposes of this documentation set, bias-free is defined as language that does not imply discrimination based on age, disability, gender, racial identity, ethnic identity, sexual orientation, socioeconomic status, and intersectionality. Exceptions may be present in the documentation due to language that is hardcoded in the user interfaces of the product software, language used based on RFP documentation, or language that is used by a referenced third-party product. Learn more about how Cisco is using Inclusive Language.
Your software release may not support all the features documented in this module. For the latest caveats and feature information, see Bug Search Tool and the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the feature information table at the end of this module.
Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/go/cfn. An account on Cisco.com is not required.
The following are the prerequisites for configuring basic IP multicast routing:
The following are the restrictions for IP multicast routing:
IP multicasting is an efficient way to use network resources, especially for bandwidth-intensive services such as audio and video. IP multicast routing enables a host (source) to send packets to a group of hosts (receivers) anywhere within the IP network by using a special form of IP address called the IP multicast group address.
The sending host inserts the multicast group address into the IP destination address field of the packet, and IP multicast routers and multilayer switches forward incoming IP multicast packets out all interfaces that lead to members of the multicast group. Any host, regardless of whether it is a member of a group, can send to a group. However, only the members of a group receive the message.
For all multicast routing protocols, the entire stack appears as a single router to the network and operates as a single multicast router.
In a switch stack, the active switch performs these functions:
The stack members perform these functions:
This table displays the default IP multicast routing configuration.
The MBONE is the small subset of Internet routers and hosts that are interconnected and capable of forwarding IP multicast traffic. Other multimedia content is often broadcast over the MBONE. Before you can join a multimedia session, you need to know what multicast group address and port are being used for the session, when the session is going to be active, and what sort of applications (audio, video, and so forth) are required on your workstation. The MBONE Session Directory Version 2 (sdr) tool provides this information. This freeware application can be downloaded from several sites on the World Wide Web, one of which is http://www.video.ja.net/mice/index.html.
SDR is a multicast application that listens to a well-known multicast group address and port for Session Announcement Protocol (SAP) multicast packets from SAP clients, which announce their conference sessions. These SAP packets contain a session description, the time the session is active, its IP multicast group addresses, media format, contact person, and other information about the advertised multimedia session. The information in the SAP packet is displayed in the SDR Session Announcement window.
How to Configure Basic IP Multicast Routing
By default, multicast routing is disabled, and there is no default mode setting.
You must configure the PIM version and the PIM mode. The switch populates its multicast routing table and forwards multicast packets it receives from its directly connected LANs according to the mode setting.
In populating the multicast routing table, dense-mode interfaces are always added to the table. Sparse-mode interfaces are added to the table only when periodic join messages are received from downstream devices or when there is a directly connected member on the interface. When forwarding from a LAN, sparse-mode operation occurs if there is an RP known for the group. If so, the packets are encapsulated and sent toward the RP. When no RP is known, the packet is flooded in a dense-mode fashion. If the multicast traffic from a specific source is sufficient, the receiver’s first-hop router might send join messages toward the source to build a source-based distribution tree.
1.
enable
3.
ip
multicast-routing distributed
6.
ip pim {dense-mode |
sparse-mode |
sparse-dense-mode}
9.
copy running-config
startup-config
Command or Action | Purpose | |||
---|---|---|---|---|
Step 1 |
enable
Example:
Switch> enable
|
Enables privileged EXEC mode. | ||
Step 2 | configure
terminal
Example: Switch# configure terminal | |||
Step 3 | ip
multicast-routing distributed
Example: Switch(config)# ip multicast-routing distributed |
Enables IP multicast distributed switching
| ||
Step 4 | interface
interface-id
Example: Switch(config)# interface gigabitethernet 1/0/1 |
Specifies the Layer 3 interface on which you want to enable multicast routing, and enters interface configuration mode. The specified interface must be one of the following:
| ||
Step 5 | ip pim version [1 |
2]
Example: Switch(config-if)# ip pim version 2 |
Configures the PIM version on the interface. By default, Version 2 is enabled and is the recommended setting. An interface in PIMv2 mode automatically downgrades to PIMv1 mode if that interface has a PIMv1 neighbor. The interface returns to Version 2 mode after all Version 1 neighbors are shut down or upgraded.
| ||
Step 6 | ip pim {dense-mode |
sparse-mode |
sparse-dense-mode}
Example: Switch(config-if)# ip pim sparse-dense-mode |
Enables a PIM mode on the interface. By default, no mode is configured. The keywords have these meanings:
| ||
Step 7 | end
Example: Switch(config-if)# end | |||
Step 8 | show running-config
Example: Switch# show running-config | |||
Step 9 | copy running-config
startup-config
Example:
Switch# copy running-config startup-config
|
(Optional) Saves your entries in the configuration file. |
Configuring Optional IP Multicast Routing Features
You define a multicast boundary to prevent Auto-RP messages from entering the PIM domain. You create an access list to deny packets destined for 224.0.1.39 and 224.0.1.40, which carry Auto-RP information.
1.
enable
3.
access-list
access-list-number
deny
source [source-wildcard]
5.
ip multicast
boundary
access-list-number
8.
copy running-config
startup-config
Command or Action | Purpose | |||
---|---|---|---|---|
Step 1 |
enable
Example:
Switch> enable
|
Enables privileged EXEC mode. Enter your password if prompted. | ||
Step 2 | configure
terminal
Example: Switch# configure terminal | |||
Step 3 | access-list
access-list-number
deny
source [source-wildcard]
Example: Switch(config)#
access-list 12 deny 224.0.1.39
access-list 12 deny 224.0.1.40
|
Creates a standard access list, repeating the command as many times as necessary.
The access list is always terminated by an implicit deny statement for everything. | ||
Step 4 | interface
interface-id
Example:
Switch(config)# interface gigabitethernet 1/0/1
|
Specifies the interface to be configured, and enters interface configuration mode. The specified interface must be one of the following:
| ||
Step 5 | ip multicast
boundary
access-list-number
Example:
Switch(config-if)# ip multicast boundary 12
|
Configures the boundary, specifying the access list you created in Step 2.
| ||
Step 6 | end
Example: Switch(config)# end | |||
Step 7 | show running-config
Example: Switch# show running-config | |||
Step 8 | copy running-config
startup-config
Example:
Switch# copy running-config startup-config
|
(Optional) Saves your entries in the configuration file. |
For complete syntax and usage information for the commands, see the switch command reference for this release and the Cisco IOS IP Multicast Command Reference.
For more information about configuring a multicast within a Multi-VRF CE, see the IP Routing: Protocol-Independent Configuration Guide, Cisco IOS Release 15S.
Enable SAP listener support when you want to use session description and announcement protocols and applications to assist the advertisement of multicast multimedia conferences and other multicast sessions and to communicate the relevant session setup information to prospective participants.
1.
enable
2.
configure
terminal
3.
ip
sap
cache-timeout
minutes
4.
interface
type
number
5.
ip
sap
listen
6.
end
7.
clear
ip
sap
[group-address | “ session-name ”]
8.
show
ip
sap
[group-address | “ session-name ”| detail]
You can remove all contents of a particular cache, table, or database. Clearing a cache, table, or database might be necessary when the contents of the particular structure are or suspected to be invalid.
Command |
Purpose |
---|---|
clear ip cgmp |
Clears all group entries the Catalyst switches have cached. |
clear ip igmp group {group [ hostname | IP address] | vrf name group [ hostname | IP address] } |
Deletes entries from the IGMP cache. |
clear ip mroute { * | [hostname | IP address] | vrf name group [ hostname | IP address] } |
Deletes entries from the IP multicast routing table. |
clear ip pim auto-rprp address |
Clears the auto-RP cache. |
clear ip sap [group-address | “session-name”] |
Deletes the Session Directory Protocol Version 2 cache or an sdr cache entry. |
Related Topic | Document Title |
---|---|
For complete syntax and usage information for the commands used in this chapter. |
Command Reference, Cisco Release 15.2(2)E (Industrial Ethernet 3000 Switch) |
Cisco IOS commands |
|
Cisco IOS IP multicast commands |
Description | Link |
---|---|
To help you research and resolve system error messages in this release, use the Error Message Decoder tool. |
https://www.cisco.com/cgi-bin/Support/Errordecoder/index.cgi |
Standard/RFC | Title |
---|---|
RFC 1112 |
Host Extensions for IP Multicasting |
RFC 2236 |
Internet Group Management Protocol, Version 2 |
RFC 4601 |
Protocol-Independent Multicast-Sparse Mode (PIM-SM): Protocol Specification |
MIB | MIBs Link |
---|---|
All supported MIBs for this release. |
To locate and download MIBs for selected platforms, Cisco IOS releases, and feature sets, use Cisco MIB Locator found at the following URL: |
Description | Link |
---|---|
The Cisco Support website provides extensive online resources, including documentation and tools for troubleshooting and resolving technical issues with Cisco products and technologies. To receive security and technical information about your products, you can subscribe to various services, such as the Product Alert Tool (accessed from Field Notices), the Cisco Technical Services Newsletter, and Really Simple Syndication (RSS) Feeds. Access to most tools on the Cisco Support website requires a Cisco.com user ID and password. |