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You must enable basic IP multicast routing and configure the PIM version and the PIM mode. Then the software can forward multicast packets, and the switch can populate its multicast routing table.
You can configure an interface to be in PIM dense mode, sparse mode, or sparse-dense mode. The switch populates its multicast routing table and forwards multicast packets it receives from its directly connected LANs according to the mode setting. You must enable PIM in one of these modes for an interface to perform IP multicast routing. Enabling PIM on an interface also enables IGMP operation on that interface.
Note |
If you enable PIM on multiple interfaces, when most of these interfaces are not on the outgoing interface list, and IGMP snooping is disabled, the outgoing interface might not be able to sustain line rate for multicast traffic because of the extra replication. |
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.
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.
Administratively-scoped boundaries can be used to limit the forwarding of multicast traffic outside of a domain or subdomain. This approach uses a special range of multicast addresses, called administratively-scoped addresses, as the boundary mechanism. If you configure an administratively-scoped boundary on a routed interface, multicast traffic whose multicast group addresses fall in this range cannot enter or exit this interface, which provides a firewall for multicast traffic in this address range.
You can define an administratively-scoped boundary on a routed interface for multicast group addresses. A standard access list defines the range of addresses affected. When a boundary is defined, no multicast data packets are allowed to flow across the boundary from either direction. The boundary allows the same multicast group address to be reused in different administrative domains.
The IANA has designated the multicast address range 239.0.0.0 to 239.255.255.255 as the administratively-scoped addresses. This range of addresses can then be reused in domains administered by different organizations. The addresses would be considered local, not globally unique.
This table displays the default IP multicast routing configuration.
By default, multicast routing is disabled, and there is no default mode setting.
This procedure is optional.
2.
access-list {
access-list-number | deny | permit source [source-wildcard] }
Command or Action | Purpose | |||
---|---|---|---|---|
Step 1 |
configure terminal Example: Switch# configure terminal |
|||
Step 2 |
access-list {
access-list-number | deny | permit source [source-wildcard] } Example:
Switch(config)# access-list 99 permit any
|
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 3 |
interface
interface-id Example:
Switch(config)# interface gigabitEthernet1/0/1
|
Specifies the interface to be configured, and enters interface configuration mode. |
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Step 4 |
ip multicast boundary
access-list-number Example:
Switch(config-if)# ip multicast boundary 99
|
Configures the boundary, specifying the access list you created in Step 2.
|
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Step 5 |
end Example:
Switch(config-if)# end
|
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Step 6 |
show running-config Example:
Switch# show running-config
|
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Step 7 |
copy running-config startup-config Example:
Switch# copy running-config startup-config
|
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.
By default, the switch does not listen to session directory advertisements.
Beginning in privileged EXEC mode, follow these steps to enable the switch to join the default session directory group (224.2.127.254) on the interface and listen to session directory advertisements. This procedure is optional.
Command or Action | Purpose | |||
---|---|---|---|---|
Step 1 |
configure terminal Example: Switch# configure terminal |
|||
Step 2 |
interface
interface-id Example:
Switch(config)# interface gigabitethernet 1/0/1
|
Specifies the interface to be enabled for sdr, and enters interface configuration mode. |
||
Step 3 |
ip sap listen Example:
Switch(config-if)# ip sap listen
|
Enables the switch software to listen to session directory announcements.
|
||
Step 4 |
end Example:
Switch(config-if)# end
|
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Step 5 |
show running-config Example:
Switch# show running-config
|
|||
Step 6 |
copy running-config startup-config Example:
Switch# copy running-config startup-config
|
By default, entries are never deleted from the sdr cache. You can limit how long the entry remains active so that if a source stops advertising SAP information, old advertisements are not unnecessarily kept.
Command or Action | Purpose | |
---|---|---|
Step 1 |
configure terminal Example: Switch# configure terminal |
|
Step 2 |
ip sap cache-timeout
minutes Example:
Switch(config)# ip sap cache-timeout 30
|
Limits how long a Session Announcement Protocol (SAP) cache entry stays active in the cache. |
Step 3 |
end Example: Switch(config)# end |
|
Step 4 |
show running-config Example:
Switch# show running-config
|
|
Step 5 |
show ip sap Example:
Switch# show ip sap
|
|
Step 6 |
copy running-config startup-config Example:
Switch# copy running-config startup-config
|
(Optional) Saves your entries in the configuration file. To return to the default setting, use the no ip sdr cache-timeout global configuration command. To delete the entire cache, use the clear ip sdr privileged EXEC command. To display the session directory cache, use the show ip sdr privileged EXEC command. |
Command |
Purpose |
---|---|
mrinfo [ hostname | address] [ source-address | interface] mrinfo { [hostname | address] | vrf } |
Queries a multicast router or multilayer switch about which neighboring multicast devices are peering with it. |
mstat source [ destination] [ group] mstat { [hostname | address] | vrf } |
|
mtrace source [ destination] [ group] mtrace { [hostname | address] | vrf } |
Traces the path from a source to a destination branch for a multicast distribution tree for a given group. |
Configuration Examples for IP Multicast Routing
This example shows how to set up a boundary for all administratively-scoped addresses:
Switch(config)# access-list 1 deny 239.0.0.0 0.255.255.255 Switch(config)# access-list 1 permit 224.0.0.0 15.255.255.255 Switch(config)# interface gigabitethernet1/0/1 Switch(config-if)# ip multicast boundary 1
You can configure the following for your IP multicast configuration:
Related Topic | Document Title |
---|---|
For complete syntax and usage information for the commands used in this book. |
Catalyst 2960-XR Switch IP Multicast Command Reference |
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 |
---|---|
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Release | Modification |
---|---|
Cisco IOS 15.0(2)EX1 |
This feature was introduced. |