IGMP Snooping

This module describes how to enable and configure the Ethernet Virtual Connection (EVC)-based IP Multicast Internet Group Management Protocol (IGMP) Snooping feature both globally and on bridge domains.

Finding Feature Information

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.

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.

Prerequisites for IGMP Snooping

  • IGMP snooping is implemented based on layer 2 multicast frames.

  • Basic IGMP v3 snooping support (BISS) is supported.

  • POP operation for all vlan tags should be configured on EFP.

  • Bridge domain (BD) interfaces from 1 to 4094 support IGMP snooping.

  • IGMP static joins are not supported.

Autogenerated Files and Directories


Caution

Any autogenerated file in the bootflash: directory should not be deleted, renamed, moved, or altered in any way unless directed by customer support; altering these files can have unpredictable consequences for system performance.

Table 1. Autogenerated Files

File or Directory

Description

crashinfo files

A crashinfo file may appear in the bootflash: file system.

Crashinfo files are useful for tuning and troubleshooting, but are not related to router operations: you can erase them without impacting the router’s performance.

core files

The bootflash/core directory is the storage area for .core files.

Warning 
Do not erase or move the core directory.

lost+found directory

This directory is created on bootup if a system check is performed. Its appearance is completely normal and does not indicate any issues with the router.

tracelogs files

The storage area for trace files is bootflash/tracelogs.

Trace files are useful for troubleshooting; you can access trace files using diagnostic mode to gather information related to the IOS failure.

Warning 
Do not erase or move the tracelog directory.

Restrictions for IGMP Snooping

  • IGMP snooping is not supported on Bridge Domain (BD) interfaces greater than 4094.

  • Static mrouter configuration is not supported.

  • IGMP snooping is not supported for pseudowires.

  • IGMP snooping is supported only on the EFP, Trunk EFPs, port-channel EFP, and port-channel Trunk EFPs.

  • Layer2 multicast is not suported with IGMP snooping when static joins are configured in EFP or TEFP. However, Layer2 multicast with IGMP snooping is supported for dynamic joins configured on the EFP or TEFP.

  • Starting with Cisco IOS Release 3.13, for Protocol Independent Multicast (PIM) Source Specific Multicast (SSM), with Bridge Domain Interface (BDI) as Incoming Interface (IIF), IGMP Snooping is not supported on the corresponding Bridge Domain (BD).

  • Starting with Cisco IOS Release 3.13, for Protocol Independent Multicast Sparse Mode (PIM-SM), with Bridge Domain Interface BDI as Incoming Interface (IIF), IGMP Snooping is not supported on the corresponding Bridge Domain (BD) in non-Designated Router (DR) node.

Information About IGMP Snooping

IGMP Snooping

IP Multicast Internet Group Management Protocol (IGMP), which runs at Layer 3 on a multicast device, generates Layer 3 IGMP queries in subnets where the multicast traffic must be routed. IGMP (on a device) sends out periodic general IGMP queries.

IGMP Snooping is an Ethernet Virtual Circuit (EVC)-based feature set. EVC decouples the concept of VLAN and broadcast domain. An EVC is an end-to-end representation of a single instance of a Layer 2 service being offered by a provider. In the Cisco EVC framework, bridge domains are made up of one or more Layer 2 interfaces known as service instances. A service instance is the instantiation of an EVC on a given port on a given device. A service instance is associated with a bridge domain based on the configuration.

When you enable EVC-based IGMP snooping on a bridge domain, the bridge domain interface responds at Layer 2 to the IGMP queries with only one IGMP join request per Layer 2 multicast group. Each bridge domain represents a Layer 2 broadcast domain. The bridge domain interface creates one entry per subnet in the Layer 2 forwarding table for each Layer 2 multicast group from which it receives an IGMP join request. All hosts interested in this multicast traffic send IGMP join requests and are added to the forwarding table entry. During a Layer 2 lookup on a bridge domain to which the bridge domain interface belongs, the bridge domain forwards the packets to the correct EFP. When the bridge domain interface hears the IGMP Leave group message from a host, it removes the table entry of the host.

IGMP snooping is supported on Metro IP and Metro Aggregate licenses on the Cisco ASR 920 Series Routers. IGMP snooping is supported with MSTP, REP, and G.8032. IGMP snooping is also supported on the port-channel interfaces.

How to Configure IGMP Snooping

Enabling IGMP Snooping

SUMMARY STEPS

  1. enable
  2. configure terminal
  3. ip igmp snooping
  4. bridge-domain bridge-id
  5. ip igmp snooping
  6. end

DETAILED STEPS

  Command or Action Purpose
Step 1

enable

Example:

Device> enable

Enables privileged EXEC mode.

  • Enter your password if prompted.

Step 2

configure terminal

Example:

Device# configure terminal

Enters global configuration mode.

Step 3

ip igmp snooping

Example:

Device(config)# ip igmp snooping

Globally enables IGMP snooping after it has been disabled.

Step 4

bridge-domain bridge-id

Example:

Device(config)# bridge-domain 100

(Optional) Enters bridge domain configuration mode.

Step 5

ip igmp snooping

Example:

Device(config-bdomain)# ip igmp snooping

(Optional) Enables IGMP snooping on the bridge domain interface being configured.

  • Required only if IGMP snooping was previously explicitly disabled on the specified bridge domain.

Step 6

end

Example:

Device(config-bdomain)# end

Returns to privileged EXEC mode.

Configuring IGMP Snooping Globally

SUMMARY STEPS

  1. enable
  2. configure terminal
  3. ip igmp snooping robustness-variable variable
  4. ip igmp snooping report-suppression
  5. ip igmp snooping last-member-query-count count
  6. ip igmp snooping last-member-query-interval interval
  7. ip igmp snooping check ttl
  8. exit

DETAILED STEPS

  Command or Action Purpose
Step 1

enable

Example:

Device> enable

Enables privileged EXEC mode.

  • Enter your password if prompted.

Step 2

configure terminal

Example:

Device# configure terminal

Enters global configuration mode.

Step 3

ip igmp snooping robustness-variable variable

Example:

Device(config)# ip igmp snooping robustness-variable 3

Configures the IGMP defined robustness variable .

Step 4

ip igmp snooping report-suppression

Example:

Device(config)# ip igmp snooping report-suppression

Enables report suppression for IGMP snooping.

Step 5

ip igmp snooping last-member-query-count count

Example:

Device(config)# ip igmp snooping last-member-query-count 5

Configures how often IGMP snooping sends query messages in response to receiving an IGMP leave message. The default is 2.

Step 6

ip igmp snooping last-member-query-interval interval

Example:

Device(config)# ip igmp snooping last-member-query-interval 200

Configures the length of time after which the group record is deleted if no reports are received. The default is 1000 milliseconds.

Step 7

ip igmp snooping check ttl

Example:

Device(config)# ip igmp snooping check ttl

Enforces IGMP snooping check.

Step 8

exit

Example:

Device(config)# exit

Exits global configuration mode and returns to privileged EXEC mode.

Configuring IGMP Snooping on a Bridge Domain

Before you begin

SUMMARY STEPS

  1. enable
  2. configure terminal
  3. bridge-domain bridge-id
  4. ip igmp snooping immediate-leave
  5. ip igmp snooping last-member-query-count count
  6. ip igmp snooping last-member-query-interval interval
  7. ip igmp snooping robustness-variable variable
  8. ip igmp snooping report-suppression
  9. ip igmp snooping check ttl
  10. end

DETAILED STEPS

  Command or Action Purpose
Step 1

enable

Example:

Device> enable

Enables privileged EXEC mode.

  • Enter your password if prompted.

Step 2

configure terminal

Example:

Device# configure terminal

Enters global configuration mode.

Step 3

bridge-domain bridge-id

Example:

Device(config)# bridge-domain 100

Enters bridge domain configuration mode.

Step 4

ip igmp snooping immediate-leave

Example:

Device(config-bdomain)# ip igmp snooping immediate-leave

Enables IGMPv2 immediate-leave processing.

Note 

When both immediate-leave processing and the query count are configured, fast-leave processing takes precedence.

Step 5

ip igmp snooping last-member-query-count count

Example:

Device(config-bdomain)# ip igmp snooping last-member-query-count 5

Sets the count for last member query messages sent in response to receiving an IGMP leave message. The valid range is 1 to 7. The default is 2 milliseconds.

Note 

When both immediate-leave processing and the query count are configured, fast-leave processing takes precedence.

Step 6

ip igmp snooping last-member-query-interval interval

Example:

Device(config-bdomain)#  ip igmp snooping last-member-query-interval 2000

Sets the last member query interval of the bridge domain. The valid range is from 100 to 32767. The default is 1000 milliseconds.

Step 7

ip igmp snooping robustness-variable variable

Example:

Device(config-bdomain)# ip igmp snooping robustness-variable 3

Configures the IGMP snooping robustness variable. The default is 2.

Step 8

ip igmp snooping report-suppression

Example:

Device(config-bdomain)# ip igmp snooping report-suppression

Enables report suppression for all hosts on the bridge domain.

Step 9

ip igmp snooping check ttl

Example:

Device(config-bdomain)# ip igmp snooping check ttl

Enforces IGMP snooping check.

Step 10

end

Example:

Device(config-bdomain)# end

Returns to privileged EXEC mode.

Disabling IGMP Snooping Globally

SUMMARY STEPS

  1. enable
  2. configure terminal
  3. no ip igmp snooping
  4. exit

DETAILED STEPS

  Command or Action Purpose
Step 1

enable

Example:

Device> enable

Enables privileged EXEC mode.

  • Enter your password if prompted.

Step 2

configure terminal

Example:

Device# configure terminal

Enters global configuration mode.

Step 3

no ip igmp snooping

Example:

Device(config)# no ip igmp snooping

Disables IGMP snooping on the router.

Step 4

exit

Example:

Device(config)# exit

Exits global configuration mode and returns to privileged EXEC mode.

Disabling IGMP Snooping on a Bridge Domain

SUMMARY STEPS

  1. enable
  2. configure terminal
  3. bridge-domain bridge-id
  4. no ip igmp snooping
  5. end

DETAILED STEPS

  Command or Action Purpose
Step 1

enable

Example:

Device> enable

Enables privileged EXEC mode.

  • Enter your password if prompted.

Step 2

configure terminal

Example:

Device# configure terminal

Enters global configuration mode.

Step 3

bridge-domain bridge-id

Example:

Device(config)# bridge-domain 4000

Enters bridge domain configuration mode.

Step 4

no ip igmp snooping

Example:

Device(config-bdomain)# no ip igmp snooping

Disables IGMP snooping on the bridge domain.

Step 5

end

Example:

Device(config-bdomain)# end

Returns to privileged EXEC mode.

Verifying IGMP Snooping

Use these commands to verify IGMP Snooping on the router.

  • show ip igmp snooping

    This command displays the IGMP snooping configuration globally on the router. The following is a sample output from the command: 

    Router# show ip igmp snooping

Global IGMP Snooping configuration:
-------------------------------------------
IGMP snooping Oper State     : Enabled
IGMPv3 snooping (minimal)    : Enabled
Report suppression           : Enabled
TCN solicit query            : Enabled
Robustness variable          : 3
Last member query count      : 2
Last member query interval   : 200
Check TTL=1                  : Yes
Check Router-Alert-Option    : No

Vlan 1:
--------
IGMP snooping Admin State           : Enabled
IGMP snooping Oper State            : Enabled
IGMPv2 immediate leave              : Disabled
Report suppression                  : Enabled
Robustness variable                 : 3
Last member query count             : 2
Last member query interval          : 200
Check TTL=1                         : Yes
Check Router-Alert-Option           : Yes
.
.
.

  • show ip igmp snooping [bd bd-id]

    This command displays configuration for IGMP snooping by bridge domain. The following is a sample output from the command: 

    Router# show ip igmp snooping bd 100

Global IGMP Snooping configuration:
-------------------------------------------
IGMP snooping Oper State     : Enabled
IGMPv3 snooping (minimal)    : Enabled
Report suppression           : Enabled
TCN solicit query            : Enabled
Robustness variable          : 3
Last member query count      : 2
Last member query interval   : 200
Check TTL=1                  : Yes
Check Router-Alert-Option    : No

Vlan 100:
--------
IGMP snooping Admin State           : Enabled
IGMP snooping Oper State            : Enabled
IGMPv2 immediate leave              : Disabled
Report suppression                  : Enabled
Robustness variable                 : 3
Last member query count             : 2
Last member query interval          : 200
Check TTL=1                         : Yes
Check Router-Alert-Option           : Yes
Query Interval                      : 0
Max Response Time                   : 10000

  • show ip igmp snooping groups bd bd-id count

    This command displays snooping information for groups by bridge domain. This is a sample output from the command: 

    Router# show ip igmp snooping group bd 4000 count

Total number of groups in Vlan 4000:   2
Total number of  (S,G) in Vlan 4000:   0

  • show ip igmp snooping groups count

    This command displays snooping information for groups. This is a sample output from the command: 

    Router# show ip igmp snooping groups count

Total number of groups:   4
Total number of  (S,G):   0

  • show ip igmp snooping counters [bd bd-id]

    This command displays IGMP snooping counters, globally or by bridge domain. This is the sample output from this command where Ovr and Und represent oversize and undersize respectively: 
    Router# show ip igmp snooping counters

Counters of group "IGMP snooping  counters                           " overall there are 15   counters 
 Type                                              | Value      | Ovr | Und
---------------------------------------------------+------------+-----+----
RX processed Query Count                           | 0          |     |     
RX processed Group Specific Query                  | 0          |     |     
RX processed Join                                  | 0          |     |     
RX processed Leave                                 | 0          |     |     
RX processed Total Valid Packets                   | 0          |     |     
RX processed Other Packets                         | 0          |     |     
RX Packets dropped for sanity errors               | 0          |     |     
RX Packets dropped for checksum errors             | 0          |     |     
RX Packets dropped for header length errors        | 0          |     |     
RX Packets dropped for other errors                | 0          |     |     
RX processed Topology change notification          | 0          |     |     
TX processed Query Count                           | 0          |     |     
TX processed Group Specific Query                  | 0          |     |     
TX processed Join                                  | 0          |     |     
TX processed Leave                                 | 0          |     |     

Counters of group "IGMP snooping  V3 counters                        " overall there are 18   counters 
RX processed V3 AllOW NEW                          | 0          |     |     
RX processed V3 BLOCK OLD                          | 0          |     |     

 Type                                              | Value      | Ovr | Und
---------------------------------------------------+------------+-----+----
RX processed V3 MODE IS INCLUDE                    | 0          |     |     
RX processed V3 MODE IS EXCLUDE                    | 0          |     |     
RX processed V3 CHANGE TO INCLUDE                  | 0          |     |     
RX processed V3 CHANGE TO EXCLUDE                  | 0          |     |     
RX processed V3 Query                              | 0          |     |     
RX processed V3 Group Specific Query               | 0          |     |     
RX processed V3 GSS Query                          | 0          |     |     
TX processed V3 ALLOW NEW                          | 0          |     |     
TX processed V3 BLOCK OLD                          | 0          |     |     
TX processed V3 MODE IS INCLUDE                    | 0          |     |     
TX processed V3 MODE IS EXCLUDE                    | 0          |     |     
TX processed V3 CHANGE TO INCLUDE                  | 0          |     |     
TX processed V3 CHANGE TO EXCLUDE                  | 0          |     |     
TX processed V3 Query                              | 0          |     |     
TX processed V3 Group Specific Query               | 0          |     |     
TX processed V3 GSS Query                          | 0          |     |

  • show ip igmp snooping mrouter

    [bd bd-id]

    This command displays multicast ports, globally or by bridge domain.. This is a sample output from the command: 

    Router# show ip igmp snooping mrouter

Vlan    ports
----    -----
100    Gi0/3/4-efp1(dynamic)
 10    Gi0/4/5-tefp1(dynamic)
100    Po64-efp100(dynamic)

  • show ip igmp snooping querier

    [bd bd-id]

    This command displays the IGMP querier information globally or by a bridge domain. This is a sample output from the command: 

    Router# show ip igmp snooping querier

Vlan      IP Address               IGMP Version   Port
-------------------------------------------------------------
100       10.0.0.2                 v2            Gi0/3/4-efp1
10        10.0.0.2                 v2            Gi0/4/5-tefp1
100       30.1.1.12                v2            Po64-efp100

  • show ip igmp snooping group

    This command displays the IGMP snooping information about multicast groups by VLAN. This is a sample output from the command: 

    Router# show ip igmp snooping  group

Flags: I -- IGMP snooping, S -- Static, P -- PIM snooping, A -- ASM mode
Vlan      Group/source             Type        Version     Port List
-----------------------------------------------------------------------
100       226.0.1.1                I           v2          Gi0/1/1-efp100  
10        225.1.1.1                I           v2          Gi0/4/2-tefp1
100       235.1.1.3                I           v2          Po64-efp1

  • show ip igmp snooping group bd

    This command displays the BD level IGMP snooping information. This is a sample output from the command: 

    Router# show ip igmp snooping  group bd 100 226.0.1.1
 
Flags: I -- IGMP snooping, S -- Static, P -- PIM snooping, A -- ASM mode
Vlan      Group/source             Type        Version     Port List
-----------------------------------------------------------------------
100       226.0.1.1                I           v2          Gi0/1/1-efp100
100       235.1.1.3                I           v2          Po64-efp1 
  
For Scale scenarios: Check the Snooping groups count per BD level.

Router# show ip igmp snooping  group bd 100 count
   
Total number of groups in Vlan 100:   1
Total number of  (S,G) in Vlan 100:   0

Additional References

Related Documents

Related Topic Document Title

Cisco IOS commands

https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/mcl/allreleasemcl/all-book.html

Standards and RFCs

Standard/RFC Title

No specific Standards and RFCs are supported by the features in this document.

—

MIBs

MIB MIBs Link
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To locate and download MIBs for selected platforms, Cisco IOS releases, and feature sets, use Cisco MIB Locator found at the following URL:

http://www.cisco.com/go/mibs

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Feature Information for IGMP Snooping

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.

Table 2. Feature Information for IGMP Snooping

Feature Name

Releases

Feature Information

IGMP Snooping

Cisco IOS XE Release 3.14.0S

This feature was introduced on the Cisco ASR 920 Series Aggregation Services Router (ASR-920-12CZ-A, ASR-920-12CZ-D, ASR-920-4SZ-A, ASR-920-4SZ-D, ASR-920-10SZ-PD, ASR-920-24SZ-IM, ASR-920-24SZ-M, ASR-920-24TZ-M) .