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This module describes how to configure configure global and per interface Internet Group Management Protocol (IGMP) state limiters to limit the number of mroute states resulting from IGMP membership reports (IGMP joins) on a global or per interface basis. Use the IGMP State Limit feature to to prevent Denial of Service (DoS) attacks or to provide a multicast CAC mechanism in network environments where all the multicast flows utilize approximately the same amount of bandwidth.
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.
You can configure only one global limit per device and one limit per interface.
The IGMP State Limit feature allows for the configuration of IGMP state limiters, which impose limits on mroute states resulting from IGMP membership reports (IGMP joins) on a global or per interface basis. Membership reports exceeding the configured limits are not entered into the IGMP cache. This feature can be used to prevent DoS attacks or to provide a multicast CAC mechanism in network environments where all the multicast flows roughly utilize the same amount of bandwidth.
Note |
IGMP state limiters impose limits on the number of mroute states resulting from IGMP, IGMP v3lite, and URL Rendezvous Directory (URD) membership reports on a global or per interface basis. |
The mechanics of IGMP state limiters are as follows:
Note |
IGMP state limiters impose limits on the number of mroute states resulting from IGMP, IGMP v3lite, and URD membership reports on a global or per interface basis. |
Perform this optional task to configure one global IGMP state limiter per device.
1. enable
2. configure terminal
3. ip igmp limit number
4. end
5. show ip igmp groups
Perform this optional task to configure a per interface IGMP state limiter.
1. enable
2. configure terminal
3. interface type number
4. ip igmp limit number [except access-list]
6. show ip igmp interface [type number]
7. show ip igmp groups
The following example shows how to configure IGMP state limiters to provide multicast CAC in a network environment where all the multicast flows roughly utilize the same amount of bandwidth.
This example uses the topology illustrated in the figure.
In this example, a service provider is offering 300 Standard Definition (SD) TV channels. Each SD channel utilizes approximately 4 Mbps.
The service provider must provision the Gigabit Ethernet interfaces on the PE router connected to the Digital Subscriber Line Access Multiplexers (DSLAMs) as follows: 50% of the link’s bandwidth (500 Mbps) must be available to subscribers of the Internet, voice, and video on demand (VoD) service offerings while the remaining 50% (500 Mbps) of the link’s bandwidth must be available to subscribers of the SD channel offerings.
Because each SD channel utilizes the same amount of bandwidth (4 Mbps), per interface IGMP state limiters can be used to provide the necessary CAC to provision the services being offered by the service provider. To determine the required CAC needed per interface, the total number of channels is divided by 4 (because each channel utilizes 4 Mbps of bandwidth). The required CAC needed per interface, therefore, is as follows:
500Mbps / 4Mbps = 125 mroutes
Once the required CAC is determined, the service provider uses the results to configure the per IGMP state limiters required to provision the Gigabit Ethernet interfaces on the PE router. Based on the network’s CAC requirements, the service provider must limit the SD channels that can be transmitted out a Gigabit Ethernet interface (at any given time) to 125. Configuring a per interface IGMP state limit of 125 for the SD channels provisions the interface for 500 Mbps of bandwidth, the 50% of the link’s bandwidth that must always be available (but never exceeded) for the SD channel offerings.
The following configuration shows how the service provider uses a per interface mroute state limiter to provision interface Gigabit Ethernet 0/0/0 for the SD channels and Internet, Voice, and VoD services being offered to subscribers:
interface GigabitEthernet0/0/0 description --- Interface towards the DSLAM --- . . . ip igmp limit 125
The 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.
Feature Name |
Releases |
Feature Information |
---|---|---|
IGMP Satet Limit |
12.2(14)S 12.2(15)T Cisco IOS XE Release 2.1 15.0(1)S |
This feature introduces the capability to limit the number of mroute states resulting from IGMP membership states on a per interface or global basis. Membership reports exceeding the configured limits are not entered into the IGMP cache. The following commands were introduced or modified: ip igmp limit (global), ip igmp limit (Interface), show ip igmp interface. |
Related Topic |
Document Title |
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Cisco IOS commands |
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Cisco IOS IP Multicast commands |
MIB |
MIBs Link |
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No new or modified MIBs are supported by this feature, and support for existing standards has not been modified by this feature. |
To locate and download MIBs for selected platforms, Cisco IOS XE releases, and feature sets, use Cisco MIB Locator found at the following URL: |
Description |
Link |
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The Cisco Support and Documentation website provides online resources to download documentation, software, and tools. Use these resources to install and configure the software and to troubleshoot and resolve technical issues with Cisco products and technologies. Access to most tools on the Cisco Support and Documentation website requires a Cisco.com user ID and password. |