Catalyst 3550 Multilayer Switch Software Configuration Guide, 12.1(12c)EA1
Configuring IGMP Snooping and MVR
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Configuring IGMP Snooping and MVR

Table Of Contents

Configuring IGMP Snooping and MVR

Understanding IGMP Snooping

Joining a Multicast Group

Leaving a Multicast Group

Immediate-Leave Processing

Configuring IGMP Snooping

Default IGMP Snooping Configuration

Enabling or Disabling IGMP Snooping

Setting the Snooping Method

Configuring a Multicast Router Port

Configuring a Host Statically to Join a Group

Enabling IGMP Immediate-Leave Processing

Displaying IGMP Snooping Information

Understanding Multicast VLAN Registration

Using MVR in a Multicast Television Application

Configuring MVR

Default MVR Configuration

MVR Configuration Guidelines and Limitations

Configuring MVR Global Parameters

Configuring MVR Interfaces

Displaying MVR Information

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 MVR


This chapter describes how to configure Internet Group Management Protocol (IGMP) snooping on your Catalyst 3550 switch, including an application of local IGMP snooping, Multicast VLAN Registration (MVR). It also includes procedures for controlling multicast group membership by using IGMP filtering.


Note For complete syntax and usage information for the commands used in this chapter, refer to the switch command reference for this release and the Cisco IOS Release Network Protocols Command Reference, Part 1, for Release 12.1.


This chapter consists of these sections:

Understanding IGMP Snooping

Configuring IGMP Snooping

Displaying IGMP Snooping Information

Understanding Multicast VLAN Registration

Configuring MVR

Displaying MVR Information

Configuring IGMP Filtering

Displaying IGMP Filtering Configuration


Note For MAC addresses that map to IP multicast groups, you can either manage them through features such as IGMP snooping and MVR, or you can use static MAC addresses. However, you cannot use both methods simultaneously. Therefore, before using IGMP snooping or MVR, you should remove all statically configured MAC addresses that map to IP multicast groups.


Understanding IGMP Snooping

Layer 2 switches can use IGMP snooping to constrain the flooding of multicast traffic by dynamically configuring Layer 2 interfaces so that multicast traffic is forwarded to only those interfaces associated with IP multicast devices. As the name implies, IGMP snooping requires the LAN switch to snoop on the IGMP transmissions between the host and the router and to keep track of multicast groups and member ports. When the switch receives an IGMP report from a host for a particular multicast group, the switch adds the host port number to the forwarding table entry; when it receives an IGMP Leave Group message from a host, it removes the host port from the table entry. It also periodically deletes entries if it does not receive IGMP membership reports from the multicast clients.


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


The multicast router (which could be a Catalyst 3550 switch with the enhanced multilayer software image) sends out periodic general queries to all VLANs. All hosts interested in this multicast traffic send join requests and are added to the forwarding table entry. The switch forwards only one join request per IP multicast group to the multicast router. It creates one entry per VLAN in the Layer 2 forwarding table for each MAC group from which it receives an IGMP join request.

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

If a port spanning-tree, a port group, or a VLAN ID change occurs, the IGMP snooping-learned multicast groups from this port on the VLAN are deleted.

Joining a Multicast Group

When a host connected to the switch wants to join an IP multicast group, it sends an unsolicited IGMP join message, specifying the IP multicast group to join. Alternatively, when the switch receives a general query from the router, it forwards the query to all ports in the VLAN. Hosts wanting to join the multicast group respond by sending a join message to the switch. The switch CPU creates a multicast forwarding-table entry for the group if it is not already present. The CPU also adds the interface where the join message was received to the forwarding-table entry. The host associated with that interface receives multicast traffic for that multicast group. See Figure 19-1.

Figure 19-1 Initial IGMP Join Message

Router A sends a general query to the switch, which forwards the query to ports 2 through 5, all members of the same VLAN. Host 1 wants to join multicast group 224.1.2.3 and multicasts an IGMP membership report (IGMP join message) to the group with the equivalent MAC destination address of 0x0100.5E01.0203. When the CPU receives the IGMP report multicast by Host 1, the CPU uses the information in the IGMP report to set up a forwarding-table entry, as shown in Table 19-1, that includes the port numbers of Host 1, the router, and the switch internal CPU.

Table 19-1 IGMP Snooping Forwarding Table

Destination Address
Type of Packet
Ports

0100.5exx.xxxx

IGMP

0

0100.5e01.0203

!IGMP

1, 2


Note that the switch hardware can distinguish IGMP information packets from other packets for the multicast group.

The first entry in the table tells the switching engine to send IGMP packets to only the switch CPU. This prevents the CPU from becoming overloaded with multicast frames.

The second entry tells the switching engine to send frames addressed to the 0x0100.5E01.0203 multicast MAC address that are not IGMP packets (!IGMP) to the router and to the host that has joined the group.

If another host (for example, Host 4) sends an unsolicited IGMP join message for the same group (Figure 19-2), the CPU receives that message and adds the port number of Host 4 to the forwarding table as shown in Table 19-2. Note that because the forwarding table directs IGMP messages to only the CPU, the message is not flooded to other ports on the switch. Any known multicast traffic is forwarded to the group and not to the CPU.

Figure 19-2 Second Host Joining a Multicast Group

Table 19-2 Updated IGMP Snooping Forwarding Table

Destination Address
Type of Packet
Ports

0100.5exx.xxxx

IGMP

0

0100.5e01.0203

!IGMP

1, 2, 5


Leaving a Multicast Group

The router sends periodic multicast general queries and the switch forwards these queries through all ports in the VLAN. Interested hosts respond to the queries. If at least one host in the VLAN wishes to receive multicast traffic, the router continues forwarding the multicast traffic to the VLAN. The switch forwards multicast group traffic to only those hosts listed in the forwarding table for that Layer 2 multicast group.

When hosts want to leave a multicast group, they can either silently leave, or they can send a leave message. When the switch receives a leave message from a host, it sends out a MAC-based general query to determine if any other devices connected to that interface are interested in traffic for the specific multicast group. The switch then updates the forwarding table for that MAC group so that only those hosts interested in receiving multicast traffic for the group are listed in the forwarding table. If the router receives no reports from a VLAN, it removes the group for the VLAN from its IGMP cache.

Immediate-Leave Processing

The switch uses IGMP snooping Immediate-Leave processing to remove from the forwarding table an interface that sends a leave message without the switch sending 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. Immediate-Leave processing ensures optimal bandwidth management for all hosts on a switched network, even when multiple multicast groups are simultaneously in use.


Note You should only use the Immediate-Leave processing feature on VLANs where a single host is connected to each port. If Immediate Leave is enabled in VLANs where more than one host is connected to a port, some hosts might be inadvertently dropped. Immediate Leave is supported with only IGMP version 2 hosts.


Configuring IGMP Snooping

IGMP snooping allows switches to examine IGMP packets and make forwarding decisions based on their content. To enable IGMP snooping on the switch to discover external multicast routers, the Layer 3 interfaces on the routers in the VLAN must already have been configured for multicast routing. For more information, see "Configuring IP Multicast Routing."

These sections describe how to configure IGMP snooping:

Default IGMP Snooping Configuration

Enabling or Disabling IGMP Snooping

Setting the Snooping Method

Configuring a Multicast Router Port

Configuring a Host Statically to Join a Group

Enabling IGMP Immediate-Leave Processing

Default IGMP Snooping Configuration

Table 19-3 shows the default IGMP snooping configuration.

Table 19-3 Default IGMP Snooping Configuration

Feature
Default Setting

IGMP snooping

Enabled globally and per VLAN

Multicast routers

None configured

Multicast router learning (snooping) method

PIM-DVMRP

IGMP snooping Immediate Leave

Disabled

Static groups

None configured


Enabling or Disabling IGMP Snooping

By default, IGMP snooping is globally enabled on the switch. When globally enabled or disabled, it is also enabled or disabled in all existing VLAN interfaces. IGMP snooping is by default enabled on all VLANs, but can be enabled and disabled on a per-VLAN basis. After you configure the VLAN interface for multicast routing, no configuration is needed for the switch to dynamically access external multicast routers by using IGMP snooping.

Global IGMP snooping overrides the VLAN IGMP snooping. If global snooping is disabled, you cannot enable VLAN snooping. If global snooping is enabled, you can enable or disable VLAN snooping.

Beginning in privileged EXEC mode, follow these steps to globally enable IGMP snooping on the switch:

 
Command
Purpose

Step 1 

configure terminal

Enter global configuration mode.

Step 2 

ip igmp snooping

Globally enable IGMP snooping in all existing VLAN interfaces.

Step 3 

end

Return to privileged EXEC mode.

Step 4 

copy running-config startup-config

(Optional) Save your entries in the configuration file.

To globally disable IGMP snooping on all VLAN interfaces, use the no ip igmp snooping global configuration command.

Beginning in privileged EXEC mode, follow these steps to enable IGMP snooping on a VLAN interface:

 
Command
Purpose

Step 1 

configure terminal

Enter global configuration mode.

Step 2 

ip igmp snooping vlan vlan-id

Enable IGMP snooping on the VLAN interface.

Step 3 

end

Return to privileged EXEC mode.

Step 4 

copy running-config startup-config

(Optional) Save your entries in the configuration file.

To disable IGMP snooping on a VLAN interface, use the no ip igmp snooping vlan vlan-id global configuration command for the specified VLAN number.

Setting the Snooping Method

Multicast-capable router ports are added to the forwarding table for every Layer 2 multicast entry. The switch learns of such ports through one of these methods:

Snooping on IGMP queries, Protocol Independent Multicast (PIM) packets, and Distance Vector Multicast Routing Protocol (DVMRP) packets

Listening to Cisco Group Management Protocol (CGMP) packets from other routers

Statically connecting to a multicast router port with the ip igmp snooping mrouter global configuration command

You can configure the switch either to snoop on IGMP queries and PIM/DVMRP packets or to listen to CGMP self-join or proxy-join packets. By default, the switch snoops on PIM/DVMRP packets on all VLANs. To learn of multicast router ports through only CGMP packets, use the ip igmp snooping vlan vlan-id mrouter learn cgmp global configuration command. When this command is entered, the router listens to only CGMP self-join and CGMP proxy-join packets and no other CGMP packets. To learn of multicast router ports through only PIM-DVMRP packets, use the ip igmp snooping vlan vlan-id mrouter learn pim-dvmrp global configuration command.


Note If you want to use CGMP as the learning method and no multicast routers in the VLAN are CGMP proxy-enabled, you must enter the ip cgmp router-only command to dynamically access the router. For more information, see "Configuring IP Multicast Routing."


Beginning in privileged EXEC mode, follow these steps to alter the method in which a VLAN interface dynamically accesses a multicast router:

 
Command
Purpose

Step 1 

configure terminal

Enter global configuration mode.

Step 2 

ip igmp snooping vlan vlan-id mrouter learn {cgmp | pim-dvmrp}

Enable IGMP snooping on a VLAN.The VLAN ID range is 1 to 4094.

Specify the multicast router learning method:

cgmp—Listen for CGMP packets. This method is useful for reducing control traffic.

pim-dvmrp—Snoop on IGMP queries and PIM-DVMRP packets. This is the default.

Step 3 

end

Return to privileged EXEC mode.

Step 4 

show ip igmp snooping

Verify the configuration.

Step 5 

copy running-config startup-config

(Optional) Save your entries in the configuration file.

This example shows how to configure IGMP snooping to use CGMP packets as the learning method:

Switch# configure terminal
Switch(config)# ip igmp snooping vlan 1 mrouter learn cgmp
Switch(config)# end       
Switch# show ip igmp snooping vlan 1
vlan 1
----------
 IGMP snooping is globally enabled
 IGMP snooping is enabled on this Vlan
 IGMP snooping immediate-leave is disabled on this Vlan
 IGMP snooping mrouter learn mode is cgmp on this Vlan
 IGMP snooping is running in IGMP_ONLY mode on this Vlan

To return to the default learning method, use the no ip igmp snooping vlan vlan-id mrouter learn cgmp global configuration command.

Configuring a Multicast Router Port

To add a multicast router port (add a static connection to a multicast router), use the ip igmp snooping vlan mrouter global configuration command on the switch.


Note Static connections to multicast routers are supported only on switch ports.


Beginning in privileged EXEC mode, follow these steps to enable a static connection to a multicast router:

 
Command
Purpose

Step 1 

configure terminal

Enter global configuration mode.

Step 2 

ip igmp snooping vlan vlan-id mrouter interface interface-id

Specify the multicast router VLAN ID and specify the interface to the multicast router.The VLAN ID range is 1 to 4094.

Step 3 

end

Return to privileged EXEC mode.

Step 4 

show ip igmp snooping mrouter [vlan vlan-id]

Verify that IGMP snooping is enabled on the VLAN interface.

Step 5 

copy running-config startup-config

(Optional) Save your entries in the configuration file.

To remove a multicast router port from the VLAN, use the no ip igmp snooping vlan vlan-id mrouter interface interface-id global configuration command.

This example shows how to enable a static connection to a multicast router and verify the configuration:

Switch# configure terminal
Switch(config)# ip igmp snooping vlan 200 mrouter interface gigabitethernet0/2
Switch(config)# end
Switch# show ip igmp snooping mrouter vlan 200
vlan            ports
-----+----------------------------------------
 200           Gi0/2(static)

Configuring a Host Statically to Join a Group

Hosts or Layer 2 ports normally join multicast groups dynamically, but you can also statically configure a host on an interface.

Beginning in privileged EXEC mode, follow these steps to add a Layer 2 port as a member of a multicast group:

 
Command
Purpose

Step 1 

configure terminal

Enter global configuration mode

Step 2 

ip igmp snooping vlan vlan-id static mac-address interface interface-id

Statically configure a Layer 2 port as a member of a multicast group:

vlan-id is the multicast group VLAN ID.

mac-address is the group MAC address.

interface-id is the member port.

Step 3 

end

Return to privileged EXEC mode.

Step 4 

show ip igmp snooping mrouter vlan vlan-id

or
show mac address-table multicast vlan vlan-id

Verify that the member port is a member of the VLAN multicast group.

Verify the member port and the MAC address

Step 5 

copy running-config startup-config

(Optional) Save your entries in the configuration file.

To remove the Layer 2 port from the multicast group, use the no ip igmp snooping vlan vlan-id static mac-address interface interface-id global configuration command.

This example shows how to statically configure a host on an interface and verify the configuration:

Switch# configure terminal
Switch(config)# ip igmp snooping vlan 1 static 0100.5e00.0203 interface gigabitethernet0/1
Switch(config)# end
Switch# show mac address-table multicast vlan 1
Vlan    Mac Address       Type       Ports
----    -----------       ----       -----
   1    0100.5e00.0203    USER       Gi0/1

Enabling IGMP Immediate-Leave Processing

When you enable IGMP Immediate-Leave processing, the switch immediately removes a port when it detects an IGMP version 2 leave message on that port. You should use the Immediate-Leave feature only when there is a single receiver present on every port in the VLAN.

Immediate Leave is supported with only IGMP version 2 hosts.

Beginning in privileged EXEC mode, follow these steps to enable IGMP Immediate-Leave processing:

 
Command
Purpose

Step 1 

configure terminal

Enter global configuration mode

Step 2 

ip igmp snooping vlan vlan-id immediate-leave

Enable IGMP Immediate-Leave processing on the VLAN interface.

Step 3 

end

Return to privileged EXEC mode.

Step 4 

show ip igmp snooping vlan vlan-id

Verify that Immediate Leave is enabled on the VLAN.

Step 5 

copy running-config startup-config

(Optional) Save your entries in the configuration file.

To disable IGMP Immediate-Leave on a VLAN, use the no ip igmp snooping vlan vlan-id immediate-leave global configuration command.

This example shows how to enable IGMP immediate-leave processing on VLAN 130 and verify the configuration:

Switch# configure terminal
Switch(config)# ip igmp snooping vlan 130 immediate-leave
Switch(config)# end
Switch# show ip igmp snooping vlan 130
vlan 130
----------
 IGMP snooping is globally enabled
 IGMP snooping is enabled on this Vlan
 IGMP snooping immediate-leave is enabled 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

Displaying IGMP Snooping Information

You can display IGMP snooping information for dynamically learned and statically configured router ports and VLAN interfaces. You can also display MAC address multicast entries for a VLAN configured for IGMP snooping.

To display IGMP snooping information, use one or more of the privileged EXEC commands in Table 19-4.

Table 19-4 Commands for Displaying IGMP Snooping Information 

Command
Purpose

show ip igmp snooping [vlan vlan-id]

Display the snooping configuration information for all VLANs on the switch or for a specified VLAN.

(Optional) Enter vlan vlan-id to display information for a single VLAN.

show ip igmp snooping mrouter [vlan vlan-id]

Display information on dynamically learned and manually configured multicast router interfaces.

Note When you enable IGMP snooping, the switch automatically learns the interface to which a multicast router is connected. These are dynamically learned interfaces.

(Optional) Enter vlan vlan-id to display information for a single VLAN.

show mac address-table multicast [vlan vlan-id] [user | igmp-snooping] [count]

Display the Layer 2 MAC address table entries for a VLAN. The keywords are all optional and limit the display as shown:

vlan vlan-id—Displays only the specified multicast group VLAN.

user—Displays only the user-configured multicast entries.

igmp-snooping—Displays only entries learned through IGMP snooping.

count—Displays only the total number of entries for the selected criteria, not the actual entries.


This is an example of output from the show ip igmp snooping privileged EXEC command for all VLAN interfaces on the switch:

Switch# show ip igmp snooping 
vlan 1
----------
 IGMP snooping is globally enabled
 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
vlan 2
----------
 IGMP snooping is globally enabled
 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
vlan 10
----------
 IGMP snooping is globally enabled
 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

This is an example of output from the show ip igmp snooping privileged EXEC command for a specific VLAN interface:

Switch# show ip igmp snooping vlan 1
vlan 1
----------
  IGMP snooping is globally enabled
  IGMP snooping is disabled on this Vlan
  IGMP snooping immediate-leave is disabled on this Vlan
  IGMP snooping mrouter learn mode is pim-dvmrp on this Vlan 

This is an example of output from the show ip igmp snooping mrouter privileged EXEC command for VLAN 1:

Switch# show ip igmp snooping mrouter vlan 1
Vlan    ports
----    -----
   1    Gi0/1(dynamic) 
   1    Gi0/2(dynamic) 

This example shows how to display the Layer 2 multicast entries for VLAN 1:

Switch# show mac address-table multicast vlan 1
vlan   mac address     type 	        ports
-----+---------------+--------+---------+---+--------------------------------
  1  0100.5e02.0203    user           Gi0/1,Gi0/2
  1  0100.5e00.0127    igmp           Gi0/1,Gi0/2
  1  0100.5e00.0128    user           Gi0/1,Gi0/2
  1  0100.5e00.0001    igmp           Gi0/1,Gi0/2

This is an example of output from the show mac address-table multicast count privileged EXEC command for the switch:

Switch# show mac address-table multicast count

Multicast MAC Entries for all vlans:    10

This is an example of output from the show mac address-table multicast count privileged EXEC command for a VLAN:

Switch# show mac address-table multicast vlan 1 count

Multicast MAC Entries for vlan 1: 

This example shows how to display only the user-configured multicast entries for VLAN 1:

Switch# show mac address-table multicast vlan 1 user 
vlan   mac address     type 	        ports
-----+---------------+--------+---------+---+--------------------------------
  1  0100.5e02.0203    user           Gi0/1,Gi0/2
  1  0100.5e00.0128    user           Gi0/1,Gi0/2

This example shows how to display the total number of entries learned by IGMP snooping for VLAN 1:

Switch# show mac address-table multicast vlan 1 igmp-snooping count

Number of user programmed entries:    2

Understanding Multicast VLAN Registration

Multicast VLAN Registration (MVR) is designed for applications using wide-scale deployment of multicast traffic across an Ethernet ring-based service provider network (for example, the broadcast of multiple television channels over a service-provider network). MVR allows a subscriber on a port to subscribe and unsubscribe to a multicast stream on the network-wide multicast VLAN. It allows the single multicast VLAN to be shared in the network while subscribers remain in separate VLANs. MVR provides the ability to continuously send multicast streams in the multicast VLAN, but to isolate the streams from the subscriber VLANs for bandwidth and security reasons.

MVR assumes that subscriber ports subscribe and unsubscribe (join and leave) these multicast streams by sending out IGMP join and leave messages. These messages can originate from an IGMP version-2-compatible host with an Ethernet connection. Although MVR operates on the underlying mechanism of IGMP snooping, the two features operate independently of each other. One can be enabled or disabled without affecting the behavior of the other feature. However, if IGMP snooping and MVR are both enabled, MVR reacts only to join and leave messages from multicast groups configured under MVR. Join and leave messages from all other multicast groups are managed by IGMP snooping.

The switch CPU identifies the MVR IP multicast streams and their associated MAC addresses in the switch forwarding table, intercepts the IGMP messages, and modifies the forwarding table to include or remove the subscriber as a receiver of the multicast stream, even though the receivers might be in a different VLAN from the source. This forwarding behavior selectively allows traffic to cross between different VLANs.

The switch has these modes of MVR operation: dynamic and compatible.

When operating in MVR dynamic mode, the switch performs standard IGMP snooping. IGMP information packets are sent to the switch CPU, but multicast data packets are not sent to the CPU. Dynamic mode allows the multicast router to run normally because the switch sends the IGMP join messages to the router, and the router forwards multicast streams for a particular group to an interface only if it has received a join message from the interface for the group. Receiver ports are treated as members of the multicast VLAN for MVR multicast control and data traffic. IGMP reports for MVR groups are sent out source ports in the multicast VLAN.

When in MVR compatible mode, MVR on the Catalyst 3550 switch interoperates with MVR on Catalyst 3500 XL and Catalyst 2900 XL switches. It works the same as dynamic mode for all multicast data packets and IGMP query and leave packets. However, received IGMP report packets for MVR groups are not sent out on the multicast VLAN source ports. In contrast to dynamic mode, the switch does not send join messages to the router. The router must be statically configured for the interface to receive the multicast stream. Therefore, in this mode, MVR does not support dynamic membership joins on source ports.

Using MVR in a Multicast Television Application

In a multicast television application, a PC or a television with a set-top box can receive the multicast stream. Multiple set-top boxes or PCs can be connected to one subscriber port, which is a switch port configured as an MVR receiver port. See Figure 19-3. DHCP assigns an IP address to the set-top box or the PC. When a subscriber selects a channel, the set-top box or PC sends an IGMP report to the S1 switch to join the appropriate multicast. If the IGMP report matches one of the configured multicast MAC addresses, the switch CPU modifies the hardware address table to include this receiver port and VLAN as a forwarding destination of the specified multicast stream when it is received from the multicast VLAN. Uplink ports that send and receive multicast data to and from the multicast VLAN are called MVR source ports.

When a subscriber changes channels or turns off the television, the set-top box sends an IGMP leave message for the multicast stream. The switch CPU sends an IGMP group-specific query through the receiver port VLAN. If there is another set-top box in the VLAN still subscribing to this group, that set-top box must respond within the maximum response time. If the CPU does not receive a response, it eliminates the receiver port as a forwarding destination for this group.

If the Immediate-Leave feature is enabled on a receiver port, the port leaves a multicast group more quickly. Without Immediate Leave, when the switch receives an IGMP leave message from a subscriber on a receiver port, it sends out an IGMP query on that port and waits for IGMP group membership reports. If no reports are received in a configured time period, the receiver port is removed from multicast group membership. With Immediate Leave, an IGMP query is not sent from the receiver port on which the IGMP leave was received. As soon as the leave message is received, the receiver port is removed from multicast group membership, which speeds up leave latency. Enable the Immediate Leave feature only on receiver ports to which a single receiver device is connected.

Figure 19-3 Multicast VLAN Registration Example

MVR eliminates the need to duplicate television-channel multicast traffic for subscribers in each VLAN. Multicast traffic for all channels is only sent around the VLAN trunk once—only on the multicast VLAN. Although the IGMP leave and join message in the VLAN to which the subscriber port is assigned. These messages dynamically register for streams of multicast traffic in the multicast VLAN on the Layer 3 device. The access layer switch (S1 switch) modifies the forwarding behavior to allow the traffic to be forwarded from the multicast VLAN to the subscriber port in a different VLAN, selectively allowing traffic to cross between two VLANs.

IGMP reports are sent to the same MAC addresses as the multicast data. The S1 CPU must capture all IGMP join and leave messages from receiver ports and forward them to the multicast VLAN of the source (uplink) port.

Configuring MVR

These sections include basic MVR configuration information:

Default MVR Configuration

MVR Configuration Guidelines and Limitations

Configuring MVR Global Parameters

Configuring MVR Interfaces

Default MVR Configuration

Table 19-5 shows the default MVR configuration.

Table 19-5 Default MVR Configuration

Feature
Default Setting

MVR

Disabled globally and per interface

Multicast addresses

None configured

Query response time

0.5 second

Multicast VLAN

VLAN 1

Mode

Compatible

Interface (per port) default

Neither a receiver nor a source port

Immediate Leave

Disabled on all ports


MVR Configuration Guidelines and Limitations

Follow these guidelines when configuring MVR:

Receiver ports cannot be trunk ports. Receiver ports on a switch can be in different VLANs, but should not belong to the multicast VLAN.

The maximum number of multicast entries that can be configured on a switch (that is, the maximum number of television channels that can be received) is 256.

Each channel is one multicast stream destined for a unique IP multicast address. These IP addresses cannot alias between themselves or with the reserved IP multicast addresses (in the range 224.0.0.xxx).

Multicast routing and MVR cannot coexist on a switch. If you enable multicast routing and a multicast routing protocol while MVR is enabled, MVR is disabled, and you receive a warning message. If you try to enable MVR while multicast routing and a multicast routing protocol are enabled, the operation to enable MVR is cancelled, and you receive an error message.


Note For complete syntax and usage information for the commands used in this section, refer to the command reference for this release.


Configuring MVR Global Parameters

You do not need to set the optional MVR parameters if you choose to use the default settings. If you do want to change the default parameters (except for the MVR VLAN), you must first enable MVR.

Beginning in privileged EXEC mode, follow these steps to configure MVR parameters:

 
Command
Purpose

Step 1 

configure terminal

Enter global configuration mode.

Step 2 

mvr

Enable MVR on the switch.

Step 3 

mvr group ip-address [count]

Configure an IP multicast address on the switch or use the count parameter to configure a contiguous series of MVR group addresses (the range for count is 1 to 256; the default is 1). Any multicast data sent to this address is sent to all source ports on the switch and all receiver ports that have elected to receive data on that multicast address. Each multicast address would correspond to one television channel.

Note Each IP address translates to a multicast 48-bit MAC address. If an IP address being configured translates (aliases) to a previously configured MAC address or to any reserved multicast MAC addresses, the command fails.

Step 4 

mvr querytime value

(Optional) Define the maximum time to wait for IGMP report memberships on a receiver port before removing the port from multicast group membership. The value is in units of tenths of a second. The range is from 1 to 100 and the default is 5 tenths or one-half second.

Step 5 

mvr vlan vlan-id

(Optional) Specify the VLAN in which multicast data is received; all source ports must belong to this VLAN. The VLAN range is 1 to 4094.
The default is VLAN 1.

Step 6 

mvr mode {dynamic | compatible}

(Optional) Specify the MVR mode of operation:

dynamic—Allows dynamic MVR membership on source ports.

compatible—Is compatible with Catalyst 3500 XL and Catalyst 2900 XL switches and does not support IGMP dynamic joins on source ports.

The default is compatible mode.

Step 7 

end

Return to privileged EXEC mode.

Step 8 

show mvr

or

show mvr members

Verify the configuration.

Step 9 

copy running-config startup-config

(Optional) Save your entries in the configuration file.

To return the switch to its default settings, use the no mvr [mode | group ip-address | querytime | vlan] global configuration commands.

This example shows how to enable MVR, configure the MVR group address, set the query time to 1 second (10 tenths), specify the MVR multicast VLAN as VLAN 22, set the MVR mode as dynamic, and verify the results:

Switch(config)# mvr
Switch(config)# mvr group 228.1.23.4
Switch(config)# mvr querytime 10
Switch(config)# mvr vlan 22 
Switch(config)# mvr mode dynamic 
Switch(config)# end 
Switch# show mvr
MVR Running: TRUE
MVR multicast vlan: 22
MVR Max Multicast Groups: 256
MVR Current multicast groups: 1
MVR Global query response time: 10 (tenths of sec)
MVR Mode: dynamic 

You can use the show mvr members privileged EXEC command to verify the MVR multicast group addresses on the switch.

Configuring MVR Interfaces

Beginning in privileged EXEC mode, follow these steps to configure Layer 2 MVR interfaces:

 
Command
Purpose

Step 1 

configure terminal

Enter global configuration mode.

Step 2 

mvr

Enable MVR on the switch.

Step 3 

interface interface-id

Enter interface configuration mode, and enter the type and number of the Layer 2 port to configure; for example, enter gi0/1 or gigabitethernet 0/1 for Gigabit Ethernet port 1.

Step 4 

mvr type {source | receiver}

Configure an MVR port as one of these:

source—Configure uplink ports that receive and send multicast data as source ports. Subscribers cannot be directly connected to source ports. All source ports on a switch belong to the single multicast VLAN.

receiver—Configure a port as a receiver port if it is a subscriber port and should only receive multicast data. It does not receive data unless it becomes a member of the multicast group, either statically or by using IGMP leave and join messages. Receiver ports cannot belong to the multicast VLAN.

The default configuration is as a non-MVR port. If you attempt to configure a non-MVR port with MVR characteristics, the operation fails.

Step 5 

mvr vlan vlan-id group ip-address

(Optional) Statically configure a port to receive multicast traffic sent to the multicast VLAN and the IP multicast address. A port statically configured as a member of a group remains a member of the group until statically removed.

Note In compatible mode, this command applies to only receiver ports. In dynamic mode, it applies to receiver ports and source ports.

Receiver ports can also dynamically join multicast groups by using IGMP join and leave messages.

Step 6 

mvr immediate

(Optional) Enable the Immediate Leave feature of MVR on the port.

Note This command applies to only receiver ports and should only be enabled on receiver ports to which a single receiver device is connected.

Step 7 

end

Return to privileged EXEC mode.

Step 8 

show mvr

show mvr interface

or

show mvr members

Verify the configuration.

Step 9 

copy running-config startup-config

(Optional) Save your entries in the configuration file.

To return the interface to its default settings, use the no mvr [type | immediate | vlan vlan-id | group] interface configuration commands.

This example shows how to configure Gigabit Ethernet port 0/2 as a receiver port, statically configure the port to receive multicast traffic sent to the multicast group address, configure Immediate Leave on the interface, and verify the results.

Switch(config)# mvr
Switch(config)# interface gigabitethernet0/2
Switch(config-if)# mvr type receiver
Switch(config-if)# mvr vlan 22 group 228.1.23.4
Switch(config-if)# mvr immediate
Switch(config)# end 
Switch# show mvr interface gigabitethernet0/2
Type: RECEIVER Status: ACTIVE Immediate Leave: ENABLED 

This is an example of output from the show mvr interface privileged EXEC command when the member keyword is included:

Switch# show mvr interface gigabitethernet0/6 members
239.255.0.0     DYNAMIC ACTIVE
239.255.0.1     DYNAMIC ACTIVE
239.255.0.2     DYNAMIC ACTIVE
239.255.0.3     DYNAMIC ACTIVE
239.255.0.4     DYNAMIC ACTIVE
239.255.0.5     DYNAMIC ACTIVE
239.255.0.6     DYNAMIC ACTIVE
239.255.0.7     DYNAMIC ACTIVE
239.255.0.8     DYNAMIC ACTIVE
239.255.0.9     DYNAMIC ACTIVE

Displaying MVR Information

You can display MVR information for the switch or for a specified interface.

Beginning in privileged EXEC mode, use the commands in Table 19-6 to display MVR configuration:

Table 19-6 Commands for Displaying MVR Information

show mvr

Displays MVR status and values for the switch—whether MVR is enabled or disabled, the multicast VLAN, the maximum (256) and current (0 through 256) number of multicast groups, the query response time, and the MVR mode.

show mvr interface [interface-id] [members [vlan vlan-id]]

Displays all MVR interfaces and their MVR configurations.

When a specific interface is entered, displays this information:

Type—Receiver or Source

Status—One of these:

Active means the port is part of a VLAN.

Up/Down means that the port is forwarding or nonforwarding.

Inactive means that the port is not part of any VLAN.

Immediate Leave—Enabled or Disabled

If the members keyword is entered, displays all multicast group members on this port or, if a VLAN identification is entered, all multicast group members on the VLAN. The VLAN ID range is 1 to 4094; do not enter leading zeros.

show mvr members [ip-address]

Displays all receiver ports that are members of any IP multicast group or the specified IP multicast group IP address.


This is an example of output from the show mvr privileged EXEC command:

Switch# show mvr
MVR Running: TRUE
MVR multicast vlan: 1
MVR Max Multicast Groups: 256
MVR Current multicast groups: 256
MVR Global query response time: 5 (tenths of sec)
MVR Mode: compatible 

This is an example of output from the show mvr interface privileged EXEC command:

Switch# show mvr interface
Port    Type            Status          Immediate Leave

---- ---- ------- ---------------

Fa0/1   SOURCE          ACTIVE/UP       DISABLED
Fa0/2   SOURCE          ACTIVE/UP       DISABLED
Fa0/3   SOURCE          ACTIVE/DOWN     DISABLED
Fa0/5   SOURCE          ACTIVE/DOWN     DISABLED

This is an example of output from the show mvr interface privileged EXEC command for a specified interface:

Switch# show mvr interface fastethernet0/2
224.0.1.1       DYNAMIC ACTIVE

This is an example of output from the show mvr interface privileged EXEC command when the members keyword is included:

Switch# show mvr interface gigabitethernet0/6 members
239.255.0.0     DYNAMIC ACTIVE
239.255.0.1     DYNAMIC ACTIVE
239.255.0.2     DYNAMIC ACTIVE
239.255.0.3     DYNAMIC ACTIVE
239.255.0.4     DYNAMIC ACTIVE
239.255.0.5     DYNAMIC ACTIVE
239.255.0.6     DYNAMIC ACTIVE
239.255.0.7     DYNAMIC ACTIVE
239.255.0.8     DYNAMIC ACTIVE
239.255.0.9     DYNAMIC ACTIVE
 
   

This is an example of output from the show mvr members privileged EXEC command:

Switch# show mvr members
MVR Group IP    Status          Members
------------    ------          -------
224.0.1.1       ACTIVE          Fa0/1(s), Fa0/2(d)
224.0.1.2       ACTIVE          Fa0/1(s)
224.0.1.3       ACTIVE          Fa0/1(s)
224.0.1.4       ACTIVE          Fa0/1(s)
224.0.1.5       ACTIVE          Fa0/1(s)
<output truncated>

Configuring IGMP Filtering

In some environments, for example metropolitan or multiple-dwelling unit (MDU) installations, an administrator might want to control the set of 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, 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 group specific query and membership reports, including join and leave reports. It does not control general IGMP queries. IGMP filtering has no relationship with the function that directs the forwarding of IP multicast traffic. The filtering feature operates in the same manner whether CGMP or MVR is used to forward the multicast traffic.

You can also set the maximum number of IGMP groups that a Layer 2 interface can join.

Default IGMP Filtering Configuration

Table 19-7 shows the default IGMP filtering configuration.

Table 19-7 Default IGMP Filtering Configuration 

Feature
Default Setting

IGMP filters

None applied

IGMP Maximum number of IGMP groups

No maximum set

IGMP profiles

None defined

IGMP profile action

Deny the range addresses


Configuring IGMP Profiles

To configure an IGMP profile, use the ip igmp profile global configuration command with a profile number to create an IGMP profile and to enter IGMP profile configuration mode. From this 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 by 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 a start and an end address.

The default is for the switch to have no IGMP profiles configured. When a profile is configured, if neither the permit nor deny keyword is included, the default is to deny access to the range of IP addresses.

Beginning in privileged EXEC mode, follow these steps to create an IGMP profile:

 
Command
Purpose

Step 1 

configure terminal

Enter global configuration mode.

Step 2 

ip igmp profile profile number

Enter IGMP profile configuration mode, and assign a number to the profile you are configuring. The range is from 1 to 4294967295.

Step 3 

permit | deny

(Optional) Set 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 

range ip multicast address

Enter 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 

end

Return to privileged EXEC mode.

Step 6 

show ip igmp profile profile number

Verify the profile configuration.

Step 7 

copy running-config startup-config

(Optional) Save 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 was to deny (the default), it would not appear in the show ip igmp profile output display.

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 IGMP profiles to Layer 2 ports only; you cannot apply IGMP profiles to routed ports or SVIs. You cannot apply profiles to ports that belong to an EtherChannel port group. You can apply a profile to multiple interfaces, but each interface can only have one profile applied to it.

Beginning in privileged EXEC mode, follow these steps to apply an IGMP profile to a switch port:

 
Command
Purpose

Step 1 

configure terminal

Enter global configuration mode.

Step 2 

interface interface-id

Enter interface configuration mode, and enter the physical interface to configure, for example fastethernet0/3. The interface must be a Layer 2 port that does not belong to an EtherChannel port group.

Step 3 

ip igmp filter profile number

Apply the specified IGMP profile to the interface. The profile number can be from 1 to 4294967295.

Step 4 

end

Return to privileged EXEC mode.

Step 5 

show running configuration interface interface-id

Verify the configuration.

Step 6 

copy running-config startup-config

(Optional) Save your entries in the configuration file.

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

This example shows how to apply IGMP profile 4 to an interface and verify the configuration.

Switch(config)# interface fastethernet0/12
Switch(config-if)# ip igmp filter 4
Switch(config-if)# end
Switch# show running-config interface fastethernet0/12
Building configuration...

Current configuration : 123 bytes
!
interface FastEthernet0/12
 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 mac-groups interface configuration command. Use the no form of this command to set the maximum back to the default, which is no limit.

This restriction can be applied to Layer 2 ports only; you cannot set a maximum number of IGMP groups on routed ports or SVIs. You also cannot use this command on ports that belong to an EtherChannel port group.

Beginning in privileged EXEC mode, follow these steps to apply an IGMP profile to a switch port:

 
Command
Purpose

Step 1 

configure terminal

Enter global configuration mode.

Step 2 

interface interface-id

Enter interface configuration mode, and enter the physical interface to configure, for example gigabitethernet0/1. The interface must be a Layer 2 port that does not belong to an EtherChannel group.

Step 3 

ip igmp max-groups number

Set the maximum number of IGMP groups that the interface can join. The range is from 0 to 4294967294. The default is to have no maximum set.

Step 4 

end

Return to privileged EXEC mode.

Step 5 

show running-configuration interface interface-id

Verify the configuration.

Step 6 

copy running-config startup-config

(Optional) Save 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 interface configuration command.

This example shows how to limit the number of IGMP groups that an interface can join to 25.

Switch(config)# interface fastethernet0/12
Switch(config-if)# ip igmp max-groups 25
Switch(config-if)# end
Switch# show running-config interface fastethernet0/12
Building configuration...

Current configuration : 123 bytes
!
interface FastEthernet0/12
 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 characteristics, and you can display the IGMP profile and maximum group configuration for all interfaces on the switch or for a specified interface.

Use the privileged EXEC commands in Table 19-8 to display IGMP filtering configuration:

Table 19-8 Commands for Displaying IGMP Filtering Configuration

show ip igmp profile [profile number]

Displays the specified IGMP profile or all IGMP profiles defined on the 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 output from 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 fastethernet0/12
Building configuration...
Current configuration : 123 bytes
!
interface FastEthernet0/12
 no ip address
 shutdown
 snmp trap link-status
 ip igmp max-groups 25
 ip igmp filter 4
end