Catalyst 4500 Series Switch Cisco IOS Software Configuration Guide, 12.1(13)EW - Understanding and Configuring IGMP Snooping and Filtering [Cisco Catalyst 4500 Series Switches]

Table Of Contents

Configuring IGMP Snooping and Filtering

Overview of IGMP Snooping

Fast-Leave Processing

Configuring IGMP Snooping

Default IGMP Snooping Configuration

Enabling IGMP Snooping

Configuring Learning Methods

Configuring PIM/DVMRP Learning

Configuring CGMP Learning

Configuring a Multicast Router Port Statically

Enabling IGMP Fast-Leave Processing

Configuring a Host Statically

Suppressing Multicast Flooding

IGMP Snooping Interface Configuration

IGMP Snooping Switch Configuration

Displaying IGMP Snooping Information

Displaying Multicast Router Interfaces

Displaying MAC Address Multicast Entries

Displaying IGMP Snooping Information for a VLAN Interface

Configuring IGMP Filtering

Default IGMP Filtering Configuration

Configuring IGMP Profiles

Applying IGMP Profiles

Setting the Maximum Number of IGMP Groups

Displaying IGMP Filtering Configuration

Configuring IGMP Snooping and Filtering

This chapter describes how to configure Internet Group Management Protocol (IGMP) snooping on the Catalyst 4500 series switch. It provides guidelines, procedures, and configuration examples.

This chapter consists of the following major sections:

•Overview of IGMP Snooping

•Configuring IGMP Snooping

•Displaying IGMP Snooping Information

•Configuring IGMP Filtering

•Displaying IGMP Filtering Configuration

Note To support Cisco Group Management Protocol (CGMP) client devices, configure the switch as a CGMP server. For more information, see the chapters "IP Multicast" and "Configuring IP Multicast Routing" in the Cisco IOS IP and IP Routing Configuration Guide, Release 12.1 at:
http://www.cisco.com/univercd/cc/td/doc/product/software/ios121/121cgcr/ip_c/ipcprt3/1cdmulti.htm

Note For complete syntax and usage information for commands used in this chapter, refer to the Catalyst 4500 Series Switch Cisco IOS Command Reference and the additional publications at this URL: http://www.cisco.com/univercd/cc/td/doc/product/software/ios121/121cgcr/index.htm

Overview of IGMP Snooping

Note Quality of service does not apply to IGMP packets when IGMP snooping is enabled.

IGMP snooping allows a switch to snoop or capture information from IGMP packets being sent back and forth between hosts and a router. Based on this information, a switch will add/delete multicast addresses from its address table, thereby enabling/disabling multicast traffic from flowing to individual host ports.

In subnets where you have configured IGMP, IGMP snooping manages multicast traffic at Layer 2. You can configure interfaces using the switchport keyword to dynamically forward multicast traffic only to those interfaces that want to receive it.

IGMP snooping restricts traffic in MAC multicast groups 0100.5e00.0001 to 01-00-5e-ff-ff-ff. IGMP snooping does not restrict Layer 2 multicast packets generated by routing protocols.

Note For more information on IP multicast and IGMP, refer to RFC 1112 and RFC 2236.

IGMP (on a router) periodically sends out general IGMP queries. When you enable IGMP snooping, the switch responds at Layer 2 to the IGMP queries with only one IGMP join request per Layer 2 multicast group. The switch 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.

Layer 2 multicast groups learned through IGMP snooping are dynamic. However, you can statically configure Layer 2 multicast groups using the ip igmp snooping static command. If you specify group membership for a multicast group address statically, your static setting supersedes any automatic manipulation by IGMP snooping. Multicast group membership lists can consist of both user-defined settings and IGMP snooping.

Groups with IP addresses in the 224.0.0—255 range are reserved for routing control packets and are flooded to all forwarding ports of the VLAN. These addresses map to the multicast MAC address range 0100.5E00.0001 to 0100.5E00.00FF.

Note If a spanning-tree topology change occurs in a VLAN, IP multicast traffic floods in all ports in the VLAN where PortFast is not enabled for two general query intervals.

In order for a host connected to a Layer 2 interface to join an IP multicast group, the host sends an IGMP join request specifying the IP multicast group. For a host to leave a multicast group, it can either ignore the periodic general IGMP queries or it can send an IGMP leave message. When the switch receives an IGMP leave message from a host, it sends out a mac-based-general IGMP query to determine whether any devices connected to that interface are interested in traffic for the specific multicast group. The switch then updates the table entry for that Layer 2 multicast group so that only those hosts interested in receiving multicast traffic for the group are listed.

Fast-Leave Processing

IGMP snooping fast-leave processing allows the switch to remove an interface from the forwarding-table entry without first sending out mac-based-general queries to the interface. The VLAN interface is pruned from the multicast tree for the multicast group specified in the original leave message. Fast-leave processing ensures optimal bandwidth management for all hosts on a switched network, even when multiple multicast groups are being used simultaneously.

When a switch with IGMP snooping enabled receives an IP mac-based-general IGMPv2 leave message, it sends a mac-based-general query out the interface where the leave message was received to determine when there are any other hosts attached to that interface that are interested in the MAC multicast group. The interface is removed from the port list of the (mac-group, VLAN) entry in the Layer 2 forwarding table, if the following conditions apply:

•If the switch does not receive an IGMP join message within the query-response-interval

•If none of the other 31 IP groups corresponding to the MAC group is interested in the multicast traffic for that MAC group

•If no multicast routers have been learned on the interface

With fast-leave enabled on the VLAN, an interface can be removed immediately from the port list of the Layer 2 entry when the IGMP leave message is received, unless a multicast router was learned on the port.

Note Use fast-leave processing only on VLANs where only one host is connected to each interface. If fast-leave is enabled in VLANs where more than one host is connected to an interface, some hosts might be dropped inadvertently. Immediate-leave processing is supported only with IGMP version 2 hosts.

Configuring IGMP Snooping

Note To use IGMP snooping, configure a Layer 3 interface in the subnet for multicast routing (see "Understanding and Configuring IP Multicast").

Note When you are configuring IGMP, configure the VLAN in the VLAN database mode (see "Understanding and Configuring VLANs").

IGMP snooping allows switches to examine IGMP packets and make forwarding decisions based on their content.

These sections describe how to configure IGMP snooping:

•Default IGMP Snooping Configuration

•Enabling IGMP Snooping

•Configuring Learning Methods

•Configuring a Multicast Router Port Statically

•Enabling IGMP Fast-Leave Processing

•Configuring a Host Statically

•Suppressing Multicast Flooding

Default IGMP Snooping Configuration

Table 15-1 shows the IGMP snooping default configuration values.

Table 15-1 IGMP Snooping Default Configuration Values

Feature

Default Value

IGMP snooping

Enabled

Multicast routers

None configured

IGMP snooping learning method

PIM/DVMRP¹

¹PIM/DVMRP = Protocol Independent Multicast/Distance Vector Multicast Routing Protocol

Enabling IGMP Snooping

To enable IGMP snooping globally, perform this task:
Command

Purpose
Step 1
Switch(config)# [no] ip igmp snooping 
Enables IGMP snooping.

Use the no keyword to disable IGMP snooping.
Step 2
Switch(config)# end 
Exits configuration mode.
Step 3
Switch# show ip igmp snooping | include globally 
Verifies the configuration.
This example shows how to enable IGMP snooping globally and verify the configuration:
Switch(config)# ip igmp snooping 
Switch(config)# end 
Switch# show ip igmp snooping | include globally 
  IGMP snooping is globally enabled
Switch#
To enable IGMP snooping in a VLAN, perform this task:
Command

Purpose
Step 1
Switch(config)# [no] ip igmp snooping vlan vlan_ID 
Enables IGMP snooping.

Use the no keyword to disable IGMP snooping.
Step 2
Switch(config)# end 
Exits configuration mode.
Step 3
Switch# show ip igmp snooping vlan vlan_ID
Verifies the configuration.
This example shows how to enable IGMP snooping on VLAN 200 and verify the configuration:
Switch# configure terminal
Switch(config)# ip igmp snooping vlan 200
Switch(config)# end 
Switch# show ip igmp snooping vlan 200 
vlan 200
IGMP snooping is globally enabled
IGMP snooping is enabled on this VLAN
IGMP snooping intermediate-leave is disabled on this VLAN
IGMP snooping mrouter learn mode is pim-dvmrp on this VLAN
IGMP snooping is running in IGMP_ONLY mode on the VLAN
Switch#
Configuring Learning Methods

The following sections describe IGMP snooping learning methods:

•Configuring PIM/DVMRP Learning

•Configuring CGMP Learning

Configuring PIM/DVMRP Learning

To configure IGMP snooping to learn from PIM/DVMRP packets, perform this task:
Command

Purpose
Switch(config)# ip igmp snooping vlan 
vlan_ID mrouter learn [cgmp | pim-dvmrp] 
Specifies the learning method for the VLAN.
This example shows how to configure IP IGMP snooping to learn from PIM/DVMRP packets:
Switch(config)# ip igmp snooping vlan 1 mrouter learn pim-dvmrp 
Switch(config)# end 
Switch#
Configuring CGMP Learning

To configure IGMP snooping to learn from CGMP self-join packets, perform this task:
Command

Purpose
Switch(config)# ip igmp snooping vlan 
vlan_ID mrouter learn [cgmp | pim-dvmrp] 
Specifies the learning method for the VLAN.
This example shows how to configure IP IGMP snooping to use CGMP self-join packets as the learning method:
Switch(config)# ip igmp snooping vlan 1 mrouter learn cgmp 
Switch(config)# end 
Switch#
Configuring a Multicast Router Port Statically

To configure a static connection to a multicast router, enter the ip igmp snooping mrouter command on the switch instead of the ip cgmp router-only command.

To configure a static connection to a multicast router, perform this task:
Command

Purpose
Step 1
Switch(config)# ip igmp snooping vlan vlan_ID 
mrouter interface interface_num 
Specifies a static connection to a multicast router for the VLAN.

Note The interface to the router must be in the VLAN where you are entering the command. The router must be administratively up, and the line protocol must be up.
Step 2
Switch(config)# end 
Exits configuration mode.
Step 3
Switch# show ip igmp snooping mrouter vlan vlan_ID 
Verifies the configuration.
This example shows how to configure a static connection to a multicast router:
Switch(config)# ip igmp snooping vlan 200 mrouter interface fastethernet 2/10
Switch# show ip igmp snooping mrouter vlan 200
vlan   ports
-----+----------------------------------------
 200   Fa2/10
Switch# 
Enabling IGMP Fast-Leave Processing

When you enable IGMP fast-leave processing in a VLAN, the switch will remove an interface from the multicast group as soon as it detects an IGMP version 2 leave message on that interface.

To enable IGMP fast-leave processing on an interface, perform this task:
Command

Purpose
Switch(config)# ip igmp snooping vlan 
vlan_ID immediate-leave
Enables IGMP fast-leave processing in the VLAN.
This example shows how to enable IGMP fast-leave processing on interface VLAN 200 and verify the configuration:
Switch(config)# ip igmp snooping vlan 200 immediate-leave 
Configuring immediate leave on vlan 200
Switch(config)# end 
Switch# show ip igmp interface vlan 200 | include immediate-leave 
IGMP snooping fast-leave is enabled on this vlan
Switch(config)#
Configuring a Host Statically

Hosts normally join multicast groups dynamically, but you can also configure a host statically on an interface.

To configure a host statically on an interface, perform this task:
Command

Purpose
Switch(config-if)# ip igmp snooping vlan 
vlan_ID static mac_address interface 
interface_num 
Configures a host statically in the VLAN.
This example shows how to configure a host statically in VLAN 200 on interface FastEthernet 2/11:
Switch(config)# ip igmp snooping vlan 200 static 0100.5e02.0203 interface fastethernet 
2/11
Configuring port FastEthernet2/11 on group 0100.5e02.0203 vlan 200
Switch(config)# 
Suppressing Multicast Flooding

An IGMP snooping-enabled switch will flood multicast traffic to all ports in a VLAN when a spanning-tree Topology Change Notification (TCN) is received. Multicast flooding suppression enables a switch to stop sending such traffic. To support flooding suppression, a new interface command and two new global commands are introduced in release 12.1(11b)EW.

The new interface command is as follows:

[no | default] ip igmp snooping tcn flood

These are the new global commands:

[no | default] ip igmp snooping tcn flood query count [1 - 10]

[no | default] ip igmp snooping tcn query solicit

Prior to release 12.1(11b)EW, when a spanning tree topology change notification (TCN) was received by a switch, the multicast traffic was flooded to all the ports in a VLAN for a period of three IGMP query intervals. This was necessary for redundant configurations. In release 12.1(11b)EW, the default time period the switch will wait before multicast flooding will stop was changed to two IGMP query intervals.

This flooding behavior is undesirable if the switch that does the flooding has many ports that are subscribed to different groups. The traffic could exceed the capacity of the link between the switch and the end host, resulting in packet loss.

With the no ip igmp snooping tcn flood command, you can disable multicast flooding on a switch interface following a topology change. Only the multicast groups that have been joined by a port are sent to that port, even during a topology change.

With the ip igmp snooping tcn flood query count command, you can enable multicast flooding on a switch interface for a short period of time following a topology change by configuring an IGMP query threshold.

Typically, if a topology change occurs, the spanning tree root switch issues a global IGMP leave message (referred to as a "query solicitation") with the group multicast address 0.0.0.0. When a switch receives this solicitation, it floods this solicitation on all ports in the VLAN where the spanning tree change occurred. When the upstream router receives this solicitation, it immediately issues an IGMP general query.

Note To immediately issue an IGMP query in the current Cisco router IGMP implementation, the router must be CGMP server-enabled. Otherwise, the router will issue an IGMP general query at the regular interval.

With the ip igmp snooping tcn query solicit command, you can now direct a non-spanning tree root switch to issue the same query solicitation.

The following sections provide additional details on the new commands and illustrate how you can use them.

IGMP Snooping Interface Configuration

A topology change in a VLAN may invalidate previously learned IGMP snooping information. A host that was on one port before the topology change may move to another port after the topology change. The Catalyst 4500 series switch takes special actions when the topology changes in order to ensure that multicast traffic is delivered to all multicast receivers in that VLAN.

When the spanning tree protocol is running in a VLAN, a spanning tree topology change notification (TCN) is issued by the root switch in the VLAN. A Catalyst 4500 series switch that receives a TCN in a VLAN for which IGMP snooping has been enabled immediately enters into "multicast flooding mode" for a period of time until the topology restabilizes and the new locations of all multicast receivers are learned.

While in "multicast flooding mode," IP multicast traffic is delivered to all ports in the VLAN, and not restricted to those ports on which multicast group members have been detected.

Starting with 12.1(11b)EW, you can manually prevent IP multicast traffic from being flooded to a switchport by using the no ip igmp snooping tcn flood command on that port.

For trunk ports, the configuration will apply to all VLANs.

By default, multicast flooding is enabled. Use the no keyword to disable flooding, and use default to restore the default behavior (flooding is enabled).

To disable multicast flooding on an interface, perform this task:
Command

Purpose
Step 1
Switch(config)# interface {fastethernet | 
gigabitethernet} slot/port 
Selects the interface to configure.
Step 2
Switch(config-if)# no ip igmp snooping tcn flood
Disables multicast flooding on the interface when TCNs are received by the switch.

To enable multicast flooding on the interface, enter this command:
default ip igmp snooping tcn flood
Step 3
Switch(config)# end 
Exits configuration mode.
Step 4
Switch# show running interface {fastethernet | 
gigabitethernet} slot/port
Verifies the configuration.
This example shows how to disable multicast flooding on interface FastEthernet 2/11:
Switch(config)# interface fastethernet 2/11
Switch(config-if)# no ip igmp snooping tcn flood
Switch(config-if)# end
Switch#
IGMP Snooping Switch Configuration

By default, "flooding mode" persists until the switch receives two IGMP general queries. You can change this period of time by using the
ip igmp snooping tcn flood query count <n> command, where n is a number between 1 and 10.

This command operates at the global configuration level.

The default number of queries is 2. The no and default keywords restore the default.

To establish an IGMP query threshold, perform this task:
Command

Purpose
Step 1
Switch(config)#  
ip igmp snooping tcn flood query count <n>
Modifies the number of IGMP queries the switch will wait for before it stops flooding multicast traffic.

To return the switch to the default number of IGMP queries, enter this command:
default ip igmp snooping tcn flood query count .
Step 2
Switch(config)# end 
Exits configuration mode.
This example shows how to modify the switch to stop flooding multicast traffic after four queries:
Switch(config)# ip igmp snooping tcn flood query count 4
Switch(config)# end
Switch#
When a spanning tree root switch receives a topology change in an IGMP snooping-enabled VLAN, the switch issues a query solicitation that causes an IOS router to send out one or more general queries. The new command ip igmp snooping tcn query solicit causes the switch to send the query solicitation whenever it notices a topology change, even if that switch is not the spanning tree root.

This command operates at the global configuration level.

By default, query solicitation is disabled unless the switch is the spanning tree root. The default keyword restores the default behavior.

To direct a switch to send a query solicitation, perform this task:
Command

Purpose
Step 1
Switch(config)#  
ip igmp snooping tcn query solicit
Configures the switch to send a query solicitation when a TCN is detected.

To stop the switch from sending a query solicitation (if it's not a spanning tree root switch), enter this command:
no ip igmp snooping tcn query solicit
Step 2
Switch(config)# end 
Exits configuration mode.
This example shows how to configure the switch to send a query solicitation upon detecting a TCN:
Switch(config)# ip igmp snooping tcn query solicit
Switch(config)# end
Switch#
Displaying IGMP Snooping Information

The following sections tell you how to display IGMP snooping information:

•Displaying Multicast Router Interfaces

•Displaying MAC Address Multicast Entries

•Displaying IGMP Snooping Information for a VLAN Interface

Displaying Multicast Router Interfaces

When you enable IGMP snooping, the switch automatically learns to which interface the multicast routers are connected.

To display multicast router interfaces, perform this task:
Command

Purpose
Switch# show ip igmp snooping mrouter vlan 
vlan_ID 
Displays multicast router interfaces.
This example shows how to display the multicast router interfaces in VLAN 1:
Switch# show ip igmp snooping mrouter vlan 1
vlan            ports
-----+----------------------------------------
  1          Gi1/1,Gi2/1,Fa3/48,Router
Switch#
Displaying MAC Address Multicast Entries

To display MAC address multicast entries for a VLAN, perform this task:
Command

Purpose
Switch# show mac-address-table multicast 
vlan vlan_ID [count]
Displays MAC address multicast entries for a VLAN.
This example shows how to display MAC address multicast entries for VLAN 1:
Switch# show mac-address-table multicast vlan 1
Multicast Entries
 vlan    mac address     type    ports
-------+---------------+-------+-------------------------------------------
   1    0100.5e01.0101     igmp Switch,Gi6/1
   1    0100.5e01.0102     igmp Switch,Gi6/1
   1    0100.5e01.0103     igmp Switch,Gi6/1
   1    0100.5e01.0104     igmp Switch,Gi6/1
   1    0100.5e01.0105     igmp Switch,Gi6/1
   1    0100.5e01.0106     igmp Switch,Gi6/1
Switch#
This example shows how to display a total count of MAC address entries for a VLAN:
Switch# show mac-address-table multicast vlan 1 count
Multicast MAC Entries for vlan 1:    4
Switch#
Displaying IGMP Snooping Information for a VLAN Interface

To display IGMP snooping information for a VLAN interface, perform this task:
Command

Purpose
Switch# show ip igmp snooping vlan vlan_ID 
Displays IGMP snooping information on a VLAN interface.
This example shows how to display IGMP snooping information on interface VLAN 200:
Switch#show ip igmp snooping vlan 1
vlan 1
----------
 IGMP snooping is globally enabled
 IGMP snooping TCN solicit query is globally disabled
 IGMP snooping global TCN flood query count is 2
 IGMP snooping is enabled on this Vlan 
 IGMP snooping immediate-leave is disabled on this Vlan 
 IGMP snooping mrouter learn mode is pim-dvmrp on this Vlan 
 IGMP snooping is running in IGMP_ONLY mode on this Vlan
Switch# 
Configuring IGMP Filtering

In some environments, for example metropolitan or multiple-dwelling unit (MDU) installations, an administrator might want to control the multicast groups to which a user on a switch port can belong. This allows the administrator to control the distribution of multicast services, such as IP/TV, based on some type of subscription or service plan.

With the IGMP filtering feature, an administrator can exert this type of control. With this feature, you can filter multicast joins on a per-port basis by configuring IP multicast profiles and associating them with individual switch ports. An IGMP profile can contain one or more multicast groups and specifies whether access to the group is permitted or denied. If an IGMP profile denying access to a multicast group is applied to a switch port, the IGMP join report requesting the stream of IP multicast traffic is dropped, and the port is not allowed to receive IP multicast traffic from that group. If the filtering action permits access to the multicast group, the IGMP report from the port is forwarded for normal processing.

IGMP filtering controls only IGMP membership join reports and has no relationship to the function that directs the forwarding of IP multicast traffic.

You can also set the maximum number of IGMP groups that a Layer 2 interface can join with the
ip igmp max-groups <n> command.

Default IGMP Filtering Configuration

Table 15-2 shows the default IGMP filtering configuration.

Table 15-2 Default IGMP Filtering Settings

Feature

Default Setting

IGMP filters

No filtering

IGMP maximum number of IGMP groups

No limit

IGMP profiles

None defined

Configuring IGMP Profiles

To configure an IGMP profile and to enter IGMP profile configuration mode, use the ip igmp profile global configuration command. From the IGMP profile configuration mode, you can specify the parameters of the IGMP profile to be used for filtering IGMP join requests from a port. When you are in IGMP profile configuration mode, you can create the profile using these commands:

•deny: Specifies that matching addresses are denied; this is the default condition.

•exit: Exits from igmp-profile configuration mode.

•no: Negates a command or sets its defaults.

•permit: Specifies that matching addresses are permitted.

•range: Specifies a range of IP addresses for the profile. You can enter a single IP address or a range with starting and ending addresses.

By default, no IGMP profiles are configured. When a profile is configured with neither the permit nor the deny keyword, the default is to deny access to the range of IP addresses.

To create an IGMP profile for a port, perform this task:

Command

Purpose

Step 1

Switch# configure terminal

Enters global configuration mode.

Step 2

Switch(config)# ip igmp profile profile number

Enters IGMP profile configuration mode and assigns a number to the profile you are configuring. The range is from 1 to 4,294,967,295.

Step 3

Switch(config-igmp-profile)# permit | deny

(Optional) Sets the action to permit or deny access to the IP multicast address. If no action is configured, the default for the profile is to deny access.

Step 4

Switch(config-igmp-profile)# range ip multicast address

Enters the IP multicast address or range of IP multicast addresses to which access is being controlled. If entering a range, enter the low IP multicast address, a space, and the high IP multicast address.

You can use the range command multiple times to enter multiple addresses or ranges of addresses.

Step 5

Switch(config-igmp-profile)# end

Returns to privileged EXEC mode.

Step 6

Switch# show ip igmp profile profile number

Verifies the profile configuration.

Step 7

Switch# copy running-config startup-config

(Optional) Saves your entries in the configuration file.

To delete a profile, use the no ip igmp profile profile number global configuration command.

To delete an IP multicast address or range of IP multicast addresses, use the no range ip multicast address IGMP profile configuration command.

This example shows how to create IGMP profile 4 (allowing access to the single IP multicast address) and how to verify the configuration. If the action were to deny (the default), it would not appear in the show ip igmp profile command output.
Switch# config t
Switch(config)# ip igmp profile 4
Switch(config-igmp-profile)# permit
Switch(config-igmp-profile)# range 229.9.9.0
Switch(config-igmp-profile)# end
Switch# show ip igmp profile 4
IGMP Profile 4
    permit
    range 229.9.9.0 229.9.9.0
Applying IGMP Profiles

To control access as defined in an IGMP profile, use the ip igmp filter interface configuration command to apply the profile to the appropriate interfaces. You can apply a profile to multiple interfaces, but each interface can only have one profile applied to it.

Note You can apply IGMP profiles to Layer 2 ports only. You cannot apply IGMP profiles to routed ports (or SVIs) or to ports that belong to an EtherChannel port group.

To apply an IGMP profile to a switch port, perform this task:

Command

Purpose

Step 1

Switch# configure terminal

Enters global configuration mode.

Step 2

Switch(config)# interface interface-id

Enters interface configuration mode, and enter the physical interface to configure, for example fastethernet2/3. The interface must be a Layer 2 port that does not belong to an EtherChannel port group.

Step 3

Switch(config-if)# ip igmp filter profile number

Applies the specified IGMP profile to the interface. The profile number can be from 1 to 4,294,967,295.

Step 4

Switch(config-if)# end

Returns to privileged EXEC mode.

Step 5

Switch# show running configuration interface interface-id

Verifies the configuration.

Step 6

Switch# copy running-config startup-config

(Optional) Saves your entries in the configuration file.

To remove a profile from an interface, use the no ip igmp filter command.

This example shows how to apply IGMP profile 4 to an interface and verify the configuration.
Switch# config t
Switch(config)# interface fastethernet2/12
Switch(config-if)# ip igmp filter 4
Switch(config-if)# end
Switch# show running-config interface fastethernet2/12
Building configuration...
Current configuration : 123 bytes
!
interface FastEthernet2/12
 no ip address
 shutdown
 snmp trap link-status
 ip igmp max-groups 25
 ip igmp filter 4
end
Setting the Maximum Number of IGMP Groups

You can set the maximum number of IGMP groups that a Layer 2 interface can join by using the ip igmp max-groups interface configuration command. Use the no form of this command to set the maximum back to the default, which is no limit.

Note This restriction can be applied to Layer 2 ports only. You cannot set a maximum number of IGMP groups on routed ports (or SVIs) or on ports that belong to an EtherChannel port group.

To apply an IGMP profile on a switch port, perform this task:

Command

Purpose

Step 1

Switch# configure terminal

Enters global configuration mode.

Step 2

Switch(config)# interface interface-id

Enters interface configuration mode, and enter the physical interface to configure, for example gigabitethernet1/1. The interface must be a Layer 2 port that does not belong to an EtherChannel group.

Step 3

Switch(config-if)# ip igmp max-groups number

Sets the maximum number of IGMP groups that the interface can join. The range is from 0 to 4,294,967,294. By default, no maximum is set.

Step 4

Switch(config-if)# end

Returns to privileged EXEC mode.

Step 5

Switch# show running-configuration interface interface-id

Verifies the configuration.

Step 6

Switch# copy running-config startup-config

(Optional) Saves your entries in the configuration file.

To remove the maximum group limitation and return to the default of no maximum, use the no ip igmp max-groups command.

This example shows how to limit the number of IGMP groups that an interface can join to 25.
Switch# config t
Switch(config)# interface fastethernet2/12
Switch(config-if)# ip igmp max-groups 25
Switch(config-if)# end
Switch# show running-config interface fastethernet2/12
Building configuration...
Current configuration : 123 bytes
!
interface FastEthernet2/12
 no ip address
 shutdown
 snmp trap link-status
 ip igmp max-groups 25
 ip igmp filter 4
end
Displaying IGMP Filtering Configuration

You can display IGMP profile and maximum group configuration for all interfaces on the switch or for a specified interface.

Use the privileged EXEC commands in Table 15-3 to display IGMP filtering configuration:

Table 15-3 Commands to Display IGMP Filtering Configuration

Command

Purpose

Switch# show ip igmp profile [profile number]

Displays the specified IGMP profile or all IGMP profiles defined on the switch.

Switch# show running-configuration [interface interface-id]

Displays the configuration of the specified interface or all interfaces on the switch, including (if configured) the maximum number of IGMP groups to which an interface can belong and the IGMP profile applied to the interface.

This is an example of the show ip igmp profile privileged EXEC command when no profile number is entered. All profiles defined on the switch are displayed.
Switch# show ip igmp profile
IGMP Profile 3
    range 230.9.9.0 230.9.9.0
IGMP Profile 4
    permit
    range 229.9.9.0 229.255.255.255
This is an example of the show running-config privileged EXEC command when an interface is specified with IGMP maximum groups configured and IGMP profile 4 has been applied to the interface.
Switch# show running-config interface fastethernet2/12
Building configuration...
Current configuration : 123 bytes
!
interface FastEthernet2/12
 no ip address
 shutdown
 snmp trap link-status
 ip igmp max-groups 25
 ip igmp filter 4
end