IP multicast is enabled and the Protocol Independent Multicast (PIM) interfaces are configured using the tasks described in the "Configuring Basic IP Multicast" module of the IP Multicast: PIM Configuration Guide.
Multicast stub routing does not prevent the configuration of other Interior Gateway Protocols (IGPs) that do not support stub routing, such as Routing Information Protocol (RIP), Open Shortest Path First (OSPF), and Intermediate System-to-Intermediate System (IS-IS) to bypass this restriction. Multicast stub routing also does not prevent the configuration of static routing to bypass this restriction. Multicast stub routing is enforced by unicast stub routing. The proper unicast Enhanced Interior Gateway Routing Protocol (EIGRP) stub routing configuration will assist in multicast stub routing.
 Note |
For more information about unicast EIGRP stub routing, see the “Configuring EIGRP” module of the IP Routing: EIGRP Configuration Guide. |
Multicast stub routing can only be implemented in nonredundant stub network topologies.
This feature is not supported on the C9500-12Q, C9500-16X, C9500-24Q, C9500-40X models of the Cisco Catalyst 9500 Series Switches.
Multicast stub networks are those segments that receivers are directly connected to for any multicast group, even though there are receivers interested in multicast traffic beyond those segments. Multicast stub routing can only be implemented in nonredundant stub network topologies.
Multicast stub routing can be used on two types of links for multicast stub networks:
Upstream link between the stub and distribution devices--The stub device’s interface facing the distribution device has full PIM functionality; a distribution device’s interface facing the stub device does not and relies on a PIM neighbor filter or operates in PIM passive mode.
Downstream link between the stub device and interested receiver--Downstream links are connected to Layer 2 access domains, such as VLANs, or Layer 3 routed interfaces. The downstream link operates in PIM passive mode and assumes that it is the only interface on that access domain, making it the Designated Router (DR). If PIM passive mode is not supported, the downstream link relies on a PIM neighbor filter to prevent the stub device from discovering other PIM neighbors on that interface. In addition, an Interior Group Management Protocol (IGMP) helper is used to proxy IGMP reports to the distribution device’s link facing the stub device.
Implementing multicast stub routing between the stub and distribution device in PIM sparse mode (PIM-SM) environment eliminates the need to maintain the group-to-Rendezvous Point (RP) mapping cache on the stub device, and saves periodic update bandwidth--if Auto-RP or PIM bootstrap router (BSR) is used for distributing the RP information.
Multicast stub routing is intended to forward multicast traffic from the distribution device to the stub device. It is possible to have sources directly connected to the stub network, and, receivers must be directly connected to the stub device and cannot be further downstream.
Implementing multicast stub routing between the stub device and interested receivers is used to reduce the overall processing of PIM control traffic, especially as the number of stub links increases on the stub device, and to protect against DoS attacks targeted at the PIM DR.
Multicast stub routing allows such stub networks to be configured easily for multicast connectivity and provides the following benefits:
Prevents stub networks from being used for multicast transit when they are enforced by unicast stub routing (EIGRP).
Reduces overall processing of PIM control traffic.
Protects against multicast spoofing of PIM DR messages and PIM assert messages.
Note |
Multicast stub routing can only be implemented in non-redundant stub network topologies. |
The tasks in this section assume that IP multicast has been enabled and that the PIM interfaces have been configured using the tasks described in the “ Configuring Basic IP Multicast ” module.
Multicast stub routing does not prevent the configuration of other IGPs that do not support stub routing, such as RIP, OSPF, and IS-IS to bypass this restriction. Multicast stub routing also does not prevent the configuration of static routing to bypass this restriction. Multicast stub routing is enforced by unicast stub routing. The proper unicast EIGRP stub routing configuration will assist in multicast stub routing.
Multicast stub routing can only be implemented in nonredundant stub network topologies.
Perform this task to configure a stub device for multicast stub routing.
| Command or Action | Purpose | |||||||
|---|---|---|---|---|---|---|---|---|
| Step 1 |
enable Example: |
Enables privileged EXEC mode.
|
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| Step 2 |
configure terminal Example: |
Enters global configuration mode. |
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| Step 3 |
interface type number Example: |
Enters interface configuration mode. |
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| Step 4 |
Do one of the following:
Example:Example: |
|
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| Step 5 |
ip igmp helper-address ip-address Example: |
Configures the device to forward all IGMP host reports and leave messages received on the interface to the specified IP address.
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| Step 6 |
end Example: |
Returns to privileged EXEC mode. |
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| Step 7 |
show ip pim interface [type number ] Example: |
Displays information about interfaces configured for PIM.
|
Perform the following task to configure the distribution device for multicast stub routing.
| Command or Action | Purpose | |||||||
|---|---|---|---|---|---|---|---|---|
| Step 1 |
enable Example: |
Enables privileged EXEC mode.
|
||||||
| Step 2 |
configure terminal Example: |
Enters global configuration mode. |
||||||
| Step 3 |
interface type number Example: |
Enters interface configuration mode. |
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| Step 4 |
Do one of the following:
Example:Example: |
|
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| Step 5 |
end Example: |
Returns to privileged EXEC mode. |
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| Step 6 |
show ip pim interface [type number ] Example: |
Displays information about interfaces configured for PIM.
|
The following example shows the configuration of multicast stub routing in a PIM-SM environment using static RP. The example is based on the topology shown in the figure.
ip multicast-routing
!
Interface GigabitEthernet1/0
ip pim sparse-mode
ip pim neighbor-filter 1 (or ip pim passive)
!
access-list 1 deny any
!
ip pim rp-address 10.1.1.1
ip multicast-routing
!
interface Vlan100
ip pim sparse-mode
ip igmp helper-address 172.16.32.1
ip pim passive
!
interface GigabitEthernet1/0
ip pim sparse-mode
!
ip pim rp-address 10.1.1.1The following example shows the configuration of multicast stub routing in a PIM-SSM environment. The example is based on the topology shown in the figure.
ip multicast-routing
!
interface GigabitEthernet1/0
ip pim sparse-mode
ip pim neighbor-filter 1 (or ip pim passive)
!
access-list 1 deny any
!
ip pim ssm default
ip multicast-routing
!
interface Vlan100
ip pim sparse-mode
ip igmp helper-address 172.16.32.1
ip pim passive
!
interface GigabitEthernet1/0
ip pim sparse-mode
!
ip pim ssm defaultThe following table provides release information about the feature or features described in this module. This table lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.
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.|
Release |
Feature Description |
|---|---|
|
Cisco IOS XE Fuji 16.8.1a |
This feature was introduced. |
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