IGMP Snooping - Cisco€¦ · Switch(config-if-srv)# encapsulationdot1q100second-dot1q20...

IGMP Snooping

This chapter describes IGMP Snooping and procedures to configure IGMP Snooping.

• Understanding IGMP Snooping, page 1

• Joining a Multicast Group , page 2

• Configuring IGMP Snooping, page 5

• Leaving a Multicast Group, page 7

• IGMP Report Suppression, page 9

• IGMP Proxy Reporting, page 17

• L2 Address Aliasing Issue , page 18

• IGMP Snooping Interaction with LAG, page 18

• IGMP Statistics and Counters , page 19

• Alarms, page 21

Understanding IGMP SnoopingAs networks increase in size, multicast routing becomes critically important as a means to determine whichsegments require multicast traffic and which do not. IP multicasting enables IP traffic to be propagated fromone source to a number of destinations, or from many sources to many destinations. Rather than sending onepacket to each destination, one packet is sent to the multicast group identified by a single IP destination groupaddress.

Internet Group Management Protocol (IGMP) snooping restricts flooding of multicast traffic by sendingmulticast traffic only to the interfaces that are subscribed to a particular multicast group.

The Cisco ME 2600X system can use IGMP snooping to constrain the flooding of multicast traffic bydynamically configuring Layer 2 interfaces so that multicast traffic is forwarded to only those interfacesassociated with IP multicast devices. As the name implies, IGMP snooping requires the Cisco ME 2600Xsystem to snoop on the IGMP transmissions between the host and the device and to keep track of multicastgroups and member ports. When the Cisco ME 2600X system receives an IGMP report from a host for aparticular multicast group, the Cisco ME 2600X system adds the host port number to the forwarding tableentry; when it receives an IGMP Leave Group message from a host, it removes the host port from the table

Cisco ME 2600X Series Ethernet Access Switch Software Configuration Guide OL-28850-04 1

entry. It also periodically deletes entries if it does not receive IGMP membership reports from the multicastclients.

For more information on IP multicast and IGMP, see RFC 1112, RFC 2236, and RFC 3376.Note

The Cisco ME 2600X system forwards periodic general queries received from the multicast device in thebridge domain where IGMP snooping is enabled. All hosts interested in this multicast group send join requestsand are added to the forwarding table entry. The CiscoME 2600X system creates one entry per bridge domainin the IGMP snooping IP multicast forwarding table for each group from which it receives an IGMP joinrequest.

The IP multicast groups learned through IGMP snooping are dynamic.

If a port interface, EFP, and bridge domain state changes, the IGMP snooping-learned multicast groups fromthis port, EFP, and bridge domain in the bridge domain are deleted.

IGMP Versions

The Cisco ME 2600X system supports IGMP version 1, IGMP version 2, and IGMP version 3 on a bridgedomain level. The Cisco ME 2600X system does snooping using L2 multicast address and not L3 IP address.

The Cisco ME 2600X system supports IGMPv3 snooping based only on the destination multicast MACaddress and not on the the source IP address or on proxy reports.

Note

An IGMPv3 Cisco ME 2600X system provides Basic IGMPv3 Snooping Support (BISS), which includessupport for the snooping features on IGMPv1 and IGMPv2 switches and for IGMPv3 membership reportmessages. BISS constrains the flooding of multicast traffic when the network includes IGMPv3 hosts. Itconstrains traffic to approximately the same set of ports as the IGMP snooping feature on IGMPv1 or IGMPv2hosts.

Joining a Multicast GroupWhen a host connected to the Cisco ME 2600X wants to join an IP multicast group and it is an IGMP version2 or version 3 client, it sends an unsolicited IGMP join message, specifying the IP multicast group to join.Alternatively, when the Cisco ME 2600X receives a general query from the router, it forwards the query toall the EFPs in the bridge domain. IGMP hosts wanting to join the multicast group respond by sending a joinmessage to the Cisco ME 2600X . The Cisco ME 2600X CPU creates a multicast forwarding-table entry forthe group if it is not already present. The CPU also adds the interface where the join message was received

Cisco ME 2600X Series Ethernet Access Switch Software Configuration Guide2 OL-28850-04

IGMP SnoopingJoining a Multicast Group

to the forwarding-table entry. The host associated with that interface receives multicast traffic for that multicastgroup. See the figure below.

Figure 1: Initial IGMP Join Message

Router A sends a general query to the CiscoME 2600X, which forwards the query to ports 2 through 5, whichhave EFPs configured in the same bridge domain. Host 1 wants to join multicast group 224.1.2.3 andmulticastsan IGMPmembership report (IGMP joinmessage) to the group. The CiscoME 2600XCPUuses the informationin the IGMP report to set up a forwarding-table entry as shown in the table below, which includes the portnumbers connected to Host 1 and the router.

Table 1: IGMP Snooping Forwarding Table

PortsType of PacketDestination Address

1, 2IGMP224.1.2.3

The CiscoME 2600X hardware can distinguish IGMP information packets from other packets for the multicastgroup. The information in the table enables the switching engine to send frames addressed to the 224.1.2.3multicast IP address, which are not IGMP packets, 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, as shownin the figure below, the CPU receives that message and adds the port number of Host 4 to the forwarding tableas shown in the table below. Note that because the forwarding table directs IGMP messages only to the CPU,



the message is not flooded to other ports on the Cisco ME 2600X. Any known multicast traffic is forwardedto the group and not to the CPU.

Figure 2: Second Host Joining a Multicast Group

Table 2: Updated IGMP Snooping Forwarding Table

PortsType of PacketDestination Address

1, 2, 5IGMP224.1.2.3

Restrictions for IGMP Snooping

• On a Cisco ME 2600X, IGMP snooping can be configured at the bridge domain level.

• IGMP immediate-leave and IGMP report-suppression commands can be configured at the bridgedomain level.

• Static multicast device can be configured at the EFP level.

• It is mandatory to untag the packets before they enter the bridge domain. This is achieved using therewrite pop configuration at the EFP level.

• For a single tagged packet, the tag is removed using the rewrite ingress tag pop 1 symmetric commandat the EFP level.

• For a double tagged packet, the tag is removed using the rewrite ingress tag pop 2 symmetric commandat the EFP level.

• For an untagged packet, a rewrite operation is not required.

• Maximum bridge domains supported are 128, with a maximum of 2000 per group.



Configuring IGMP SnoopingTo configure IGMP snooping, complete the following procedures:

1 Enabling or Disabling IGMP Snooping, on page 5

2 Complete the following tasks as necessary:

• Enabling or Disabling IGMP Immediate Leave, on page 8

• Disabling IGMP Report Suppression, on page 10

• Configuring a Static Multicast Port, on page 11

3 (Optional) Viewing IGMP Configuration, on page 13

Enabling or Disabling IGMP Snooping

SUMMARY STEPS

1. enable2. configure terminal3. bridge domain bridge-domain value4. [no] ip igmp snooping5. end6. copy running-config startup-config

DETAILED STEPS

PurposeCommand or Action

Enables privileged EXEC mode.enableStep 1

Example:Switch> enable

• Enter your password if prompted.

Enters global configuration mode.configure terminal

Example:Switch# configure terminal

Step 2

Enters the bridge domain.bridge domain bridge-domain value

Example:Switch(config)# bridge-domain 22

Step 3

• Enter the value of the bridge-domain.


IGMP SnoopingConfiguring IGMP Snooping


Enables IGMP snooping on the bridge-domain. The noform of the command disables this function.

[no] ip igmp snooping

Example:Switch(config-bdomain)# ip igmp snooping

Step 4

Returns to the privileged EXEC mode.end

Example:Switch(config-bdomain)# end

Step 5

(Optional) Saves your entries in the configuration file.copy running-config startup-config

Example:Switch# copy running-config startup-config

Step 6

Examples:

The following example shows how to enable IGMP snooping on untagged Ethernet traffic on the bridgedomain and how to configure the source and host ports:

Configuration on the bridge-domainSwitch(config)# bridge-domain 30Switch(config-bdomain)# ip igmp snoopingConfiguration on port 1Switch(config)# interface gi 0/1Switch(config-if)# service instance 10 ethernetSwitch(config-if-srv)# encapsulation untaggedSwitch(config-if-srv)# bridge-domain 30Configuration on port 2Switch(config)# interface gi 0/5Switch(config-if)# service instance 10 ethernetSwitch(config-if-srv)# encapsulation untaggedSwitch(config-if-srv)# bridge-domain 30Configuration on port 3Switch(config)# interface gi 0/10Switch(config-if)# service instance 10 ethernetSwitch(config-if-srv)# encapsulation untaggedSwitch(config-if-srv)# bridge-domain 30The following example shows how to enable IGMP snooping on single and double tagged Ethernet traffic onthe bridge domain and how to configure the source and host ports:

Configuration on the bridge-domainSwitch(config)# bridge-domain 30Switch(config-bdomain)# ip igmp snoopingConfiguration on port 1Switch(config)# interface gi 0/1Switch(config-if)# service instance 10 ethernetSwitch(config-if-srv)# encapsulation dot1q 50 second-dot1q 10Switch(config-if-srv)# rewrite ingress pop 2 symmetricSwitch(config-if-srv)# bridge-domain 30


IGMP SnoopingEnabling or Disabling IGMP Snooping

Configuration on port 2Switch(config)# interface gi 0/2Switch(config-if)# service instance 10 ethernetSwitch(config-if-srv)# encapsulation dot1q 200Switch(config-if-srv)# rewrite ingress pop 1 symmetricSwitch(config-if-srv)# bridge-domain 30Configuration on port 3Switch(config)# interface gi 0/5Switch(config-if)# service instance 10 ethernetSwitch(config-if-srv)# encapsulation dot1q 100Switch(config-if-srv)# rewrite ingress pop 1 symmetricSwitch(config-if-srv)# bridge-domain 30The following example shows how to enable IGMP snooping on double tagged Ethernet traffic on the bridgedomain and how to configure the source and host ports::

Configuration on the bridge-domainSwitch(config)# bridge-domain 30Switch(config-bdomain)# ip igmp snoopingConfiguration on port 1Switch(config)# interface gi 0/1Switch(config-if)# service instance 10 ethernetSwitch(config-if-srv)# encapsulation dot1q 10 second-dot1q 20Switch(config-if-srv)# rewrite ingress pop 2 symmetricSwitch(config-if-srv)# bridge-domain 30Configuration on port 2Switch(config)# interface gi 0/5Switch(config-if)# service instance 10 ethernetSwitch(config-if-srv)# encapsulation dot1q 100 second-dot1q 20Switch(config-if-srv)# rewrite ingress pop 2 symmetricSwitch(config-if-srv)# bridge-domain 30Configuration on port 3Switch(config)# interface gi 0/6Switch(config-if)# service instance 10 ethernetSwitch(config-if-srv)# encapsulation dot1q 101 second-dot1q 20Switch(config-if-srv)# rewrite ingress pop 2 symmetricSwitch(config-if-srv)# bridge-domain 30

What to Do Next

Verification

To verify if the IGMP snooping is enabled on the Ethernet traffic, run the following command:show ip igmp snooping vlan 30

Leaving a Multicast GroupThe router sends periodic multicast general queries, and the Cisco ME 2600X system forwards these queriesthrough all ports in the bridge domain. Interested hosts respond to the queries. If at least one host in the bridgedomain wants to receive multicast traffic, the router continues forwarding the multicast traffic to the bridgedomain. The Cisco ME 2600X system forwards multicast group traffic only to those hosts listed in theforwarding table for that IP multicast group maintained by IGMP snooping.

When hosts want to leave a multicast group, they can leave without sending a message, or they can send aleave message. When the Cisco ME 2600X system receives a leave message from a host, it sends agroup-specific query to learn if any other devices connected to that interface are interested in traffic for thespecific multicast group. The Cisco ME 2600X system then updates the forwarding table for that MAC groupso that only those hosts interested in receiving multicast traffic for the group are listed in the forwarding table.


IGMP SnoopingLeaving a Multicast Group

If the router receives no reports from a bridge domain, it removes the group for the bridge domain from itsIGMP cache.

Immediate Leave

The Immediate Leave feature is only supported on IGMP version 2 hosts. The Cisco ME 2600X system usesIGMP Snooping Immediate Leave feature to remove an interface from the forwarding table, which sends aleave message without the Cisco ME 2600X system sending group-specific queries to the interface. TheVLAN interface is pruned from the multicast tree for the multicast group specified in the original leavemessage. The Immediate Leave feature ensures optimal bandwidth management for all hosts on a switchednetwork, even when multiple multicast groups are simultaneously in use.

You should only use the Immediate Leave feature on bridge domains where a single host is connected toeach port. If this feature is enabled on bridge domains where more than one host is connected to a port,some hosts might get dropped.

Note

Enabling or Disabling IGMP Immediate LeaveWhen you enable the IGMP Immediate Leave feature, the Cisco ME 2600X system immediately removes aport when it detects an IGMP version 2 leave message on that port. You should use the Immediate Leavefeature only when there is a single receiver present on every port in the bridge domain.

The Immediate Leave feature is supported only on IGMP version 2 hosts.Note

PrerequisiteEnabling or Disabling IGMP Snooping, on page 5

SUMMARY STEPS

1. enable2. configure terminal3. bridge domain bridge-domain value4. [no] ip igmp snooping immediate-leave5. end6. copy running-config startup-config

DETAILED STEPS






IGMP SnoopingEnabling or Disabling IGMP Immediate Leave




Step 2

Enters the bridge domain configuration mode.bridge domain bridge-domain value


Step 3

• Enter the value of the bridge domain.

Enables the IGMP Immediate Leave feature on the bridgedomain. The no form of the command disables thisfunction.

[no] ip igmp snooping immediate-leave

Example:Switch(config-bdomain)# ip igmp snoopingimmediate-leave

Step 4



Step 5



Step 6

To disable the IGMP Immediate Leave feature on a bridge domain, use the no ip igmp snoopingimmediate-leave in the bridge-domain configuration mode.

Examples:

The following example shows how to enable IGMP Immediate Leave feature for bridge-domain130:

Switch# configure terminalSwitch(config)# bridge-domain 130Switch(config-bdomain)# ip igmp snooping immediate-leaveSwitch(config-bdomain)# end

IGMP Report Suppression

IGMP report suppression is supported only when the multicast query has IGMPv1 and IGMPv2 reports.This feature is not supported when the query includes IGMPv3 reports.

Note

The Cisco ME 2600X system uses IGMP report suppression to forward only one IGMP report per multicastquery, to multicast devices. When IGMP suppression is enabled (the default), the Cisco ME 2600X systemsends the first IGMP report from all hosts for a group, to all the multicast devices. The Cisco ME 2600X


IGMP SnoopingIGMP Report Suppression

system does not send the remaining IGMP reports for the group to the multicast devices. This feature preventsduplicate reports from being sent to the multicast devices.

If the multicast device query includes requests only for IGMPv1 and IGMPv2 reports, the Cisco ME 2600Xsystem forwards only the first IGMPv1 or IGMPv2 report from all hosts for a group to all the multicast devices.

If the multicast device query also includes requests for IGMPv3 reports, the CiscoME 2600X system forwardsall IGMPv1, IGMPv2, and IGMPv3 reports for a group to the multicast devices.

If you disable IGMP report suppression, all IGMP reports are forwarded to the multicast devices.

Disabling IGMP Report Suppression

IGMP report suppression is supported only when the multicast query has IGMPv1 and IGMPv2 reports.This feature is not supported when the query includes IGMPv3 reports.

Note

IGMP report suppression is enabled by default. When it is enabled, the Cisco ME 2600X system forwardsonly one IGMP report per multicast query.When report suppression is disabled, all IGMP reports are forwardedto the multicast devices. To re-enable IGMP report suppression, use the ip igmp snooping report-suppressioncommand in the bridge domain configuration mode.


SUMMARY STEPS

1. enable2. configure terminal3. bridge domain bridge-domain value4. no ip igmp snooping report-suppression5. end6. copy running-config startup-config

DETAILED STEPS







Step 2


IGMP SnoopingDisabling IGMP Report Suppression


Enters the bridge domain configuration mode.bridge domain bridge-domain value


Step 3


Disables IGMP report suppression.no ip igmp snooping report-suppression

Example:Switch(config-bdomain)# no ip igmp snoopingreport-suppression

Step 4



Step 5



Step 6

Examples:

The following example shows how to re-enable IGMP report suppression for bridge-domain 130:

Switch# configure terminalSwitch(config-bdomain)# bridge-domain 130Switch(config-bdomain)# ip igmp snooping report-suppressionSwitch(config-bdomain)# end

Configuring a Static Multicast PortTo add a static connection to a multicast port, use the ip igmp snoopingmrouter EFP configuration commandon the CiscoME 2600X system. To remove a static multicast port from the bridge domain, use the no ip igmpsnooping mrouter configuration command.

Static connections to multicast devices are supported only at the EFP.Note



IGMP SnoopingConfiguring a Static Multicast Port

SUMMARY STEPS

1. enable2. configure terminal3. interface type slot/port4. service instance id ethernet5. encapsulation dot1q id6. rewrite ingress tag pop 1 symmetric7. bridge domain bridge-domain value8. [no] ip igmp snooping mrouter9. end

DETAILED STEPS







Step 2

Specifies the type and location of the interface to configure,where:

interface type slot/port

Example:Switch(config)# interfaceTenGigabitEthernet 0/45

Step 3

• type—Specifies the type of interface.

• slot/port—Specifies the location of the interface.

The interface can be a physical interface or a port channel. Theport-channel range is 1 to 128.

Configures an Ethernet service instance on an interface.service instance id ethernet

Example:Switch(config-if)# service instance 10ethernet

Step 4

Defines the encapsulation format as IEEE 802.1Q (dot1q) andspecifies the identifier. The identifier indicates the CVLANwithwhich the packet is received on the interface.

encapsulation dot1q id

Example:Switch(config-if)# encapsulation dot1q 10

Step 5

• Enter the value of the identifier.


IGMP SnoopingConfiguring a Static Multicast Port


Specifies the rewrite operation.rewrite ingress tag pop 1 symmetric

Example:Switch(config-if-srv)# rewrite ingress tagpop 1 symmetric

Step 6

Specifies the multicast bridge domain ID. The bridge domain IDrange is from 1 to 16384

bridge domain bridge-domain value

Example:Switch(config-if-srv)# bridge-domain 22

Step 7


Adds a static connection to the multicast device. The no form ofthe command removes the static multicast port from the bridgedomain.

[no] ip igmp snooping mrouter

Example:Switch(config-if-srv)# ip igmp snoopingmrouter

Step 8


Example:Switch(config-if-srv)# end

Step 9

Examples:

The following example shows how to enable a static connection to a multicast device:

Switch(config)# interface TenGigabitEthernet 0/45Switch(config-if)# service instance 20 ethernetSwitch(config-if-srv)# encapsulation dot1q 10Switch(config-if-srv)# rewrite ingress tag pop 1 symmetricSwitch(config-if-srv)# bridge-domain 20Switch(config-if-srv)# ip igmp snooping mrouter

The following example shows how to disable a static connection to a multicast device:

Switch(config)# interface TenGigabitEthernet 0/45Switch(config-if)# service instance 20 ethernetSwitch(config-if-srv)# no ip igmp snooping mrouter

Viewing IGMP Configuration

SUMMARY STEPS

1. enable2. show ip igmp snooping [groups [count | vlan bridge-domain ID [ ip-address | count | dynamic [count]

| user [count] ]]] | mrouter [vlan bridge-domain ID] querier | vlan bridge-domain ID]3. show ip igmp snooping querier [vlan bridge-domain ID ]


IGMP SnoopingViewing IGMP Configuration

DETAILED STEPS





Displays the IGMP snooping information.show ip igmp snooping [groups [count |vlan bridge-domain ID [ ip-address | count

Step 2

• groups—(Optional) Displays group information.| dynamic [count] | user [count] ]]] |mrouter [vlan bridge-domain ID] querier| vlan bridge-domain ID]

• count—(Optional) Displays the number of multicast groups learned byIGMP snooping.

Example:Switch# show ip igmp snooping vlan22

• vlan bridge-domain ID—(Optional) Specifies a bridge domain.

• bridge-domain ID— Bridge domain ID. Valid values are from 1 to16384.

• ip-address—(Optional) Displays information about the specified group.

• count—(Optional) Displays the group count inside a bridge domain.

• dynamic—(Optional) Displays dynamic entries learned through IGMPsnooping.

• count—(Optional) Displays the number of dynamic entries.

• user—(Optional) Displays only the user-configured multicast entries.

• count—(Optional) Displays the number of user-configured multicastentries.

• mrouter—(Optional) Displays information about dynamically learnedand manually configured multicast ports.

• querier—(Optional) Displays IGMP querier information.

Displays information about the IP address and the receiving port for the recentlyreceived IGMP query messages.

show ip igmp snooping querier [vlanbridge-domain ID ]

Example:Switch# show ip igmp snoopingquerier vlan 22

Step 3

• vlan bridge-domain ID—(Optional) Specifies a bridge domain.

• bridge-domain ID— Bridge domain ID. Valid values are from 1 to16384.

Examples

The following example displays the output of the show ip igmp snooping [vlan bridge-domain ID] command.Switch# show ip igmp snooping vlan 2



Global IGMP Snooping configuration:-------------------------------------------IGMP snooping Oper State : EnabledIGMPv3 snooping (minimal) : EnabledReport suppression : EnabledTCN solicit query : DisabledRobustness variable : 2Last member query count : 2Last member query interval : 1000Check TTL=1 : NoCheck Router-Alert-Option : No

Vlan 2-----------------------IGMP snooping Admin State : EnabledIGMP snooping Oper State : EnabledIGMPv2 immediate leave : DisabledReport suppression : EnabledRobustness variable : 2Last member query count : 2Last member query interval : 1000Check TTL=1 : YesCheck Router-Alert-Option : YesQuery Interval : 0Max Response Time : 10000

The following example displays the output of the show ip igmp snooping groups command.Switch# show ip igmp snooping groups

Flags: I -- IGMP snooping, S -- Static, P -- PIM snooping, A -- ASM mode

Vlan Group/source Type Version Port List-----------------------------------------------------------------------22 225.10.10.10 I v2 Te0/45

The following example displays the output of the show ip igmp snooping groups count command.Switch# show ip igmp snooping groups count

Total number of groups: 1

The following example displays the output of the show ip igmp snooping groups dynamic command.Switch# show ip igmp snooping groups dynamic



The following example displays the output of the show ip igmp snooping groups dynamic count command.Switch# show ip igmp snooping groups dynamic count


The following example displays the output of the show ip igmp snooping groups user command.Switch# show ip igmp snooping groups user





The following example displays the output of the show ip igmp snooping groups user count command.Switch# show ip igmp snooping groups user count


The following example displays the output of the show ip igmp snooping groups vlan command.Switch# show ip igmp snooping groups vlan 22



The following example displays the output of the show ip igmp snooping groups vlan bridge-domain ID[ip_address] command.Switch# show ip igmp snooping groups vlan 22 225.10.10.10



The following example displays the output of the show ip igmp snooping groups vlan bridge-domain ID[count] command.Switch# show ip igmp snooping groups vlan 22 count

Total number of groups in Bridge-Domain Index 22: 1

The following example displays the output of the show ip igmp snooping groups vlan bridge-domain ID[dynamic] command.Switch# show ip igmp snooping groups vlan 22 dynamic



The following example displays the output of the show ip igmp snooping groups vlan bridge-domain ID[dynamic count] command.Switch# show ip igmp snooping groups vlan 22 dynamic count

Total number of groups in Bridge-Domain Index 22: 1

The following example displays the output of the show ip igmp snooping groups vlan bridge-domain ID[user] command.Switch# show ip igmp snooping groups vlan 22 user





The following example displays the output of the show ip igmp snooping mrouter command.Switch# show ip igmp snooping mrouter

Vlan ports---- -----

2 Te0/45(dynamic)

The following example displays the output of the show ip igmp snooping mrouter vlan 2 command.Switch# show ip igmp snooping mrouter vlan 2

Vlan ports---- -----

2 Te0/45(dynamic)

The following example shows the output of the show ip igmp snooping querier command.Switch# show ip igmp snooping querier

Vlan IP Address IGMP Version Port-------------------------------------------------------------2 10.10.10.1 v2 Te0/45

The following example shows the output of the show ip igmp snooping querier [vlan bridge-domain ID]command.Switch# show ip igmp snooping querier vlan 22

IP address : 1.1.1.1IGMP version : v2Port : Gi0/41Max response time : 10s

IGMP Proxy ReportingIGMP supports proxy reporting for IGMPv1 and IGMPv2 messages to handle group-specific queries. Thesequeries are not sent downstream, but the Cisco ME 2600X system does respond to them directly. When theCisco ME 2600X system receives a group-specific query, the Cisco ME 2600X system terminates the queryand sends an IGMP proxy report if there is a receiver for the group. There is no proxy reporting for IGMPv3messages. For IGMPv3, a group-specific query or a group source-specific query is flooded to all VLANmember ports. The database for the IGMPv3 membership report is built based on the reports received.

Host reports responding to a specific query can be suppressed by the report suppression feature. Reportsuppression is supported for IGMPv1, IGMPv2 and IGMPv3 messages. With report suppression enabled (bydefault), when the Cisco ME 2600X system receives a general query, the Cisco ME 2600X system starts asuppression cycle for reports from all hosts to each group or channel. Only the first report to the discoveredmulticast devices are forwarded; the rest of the reports are suppressed. For IGMPv1 and IGMPv2, the timeof suppression is the report response time indicated in the general query message. For IGMPv3, suppressionoccurs for the entire general query interval.


IGMP SnoopingIGMP Proxy Reporting

Note • Source-based filtering for IGMP version 3 reports is not supported in hardware. The states aremaintained only in software and used for explicit host tracking and statistics collection. Thesource-only entries are deleted every 5 minutes and relearned to ensure that they are still valid.

• Turning off explicit host tracking disables fast-leave processing and proxy reporting.

L2 Address Aliasing IssueThe IGMP snooping forwarding table is based on L2 address. Since multiple IP addresses can map to thesame L2 address, an L2 address aliasing can occur. For example, IP addresses 225.1.1.1 and 226.1.1.1 mapto the same MAC address 01005E010101 which results in L2 address aliasing.

IGMP Snooping Interaction with LAGA link aggregation (LAG) interface can be added to a bridge domain, which has IGMP snooping enabled.

The following example shows how to configure the source port, which is part of the LAG interface that is amember of the bridge domain that has IGMP snooping enabled.

Configuration on the bridge-domainSwitch(config)# bridge-domain 30Switch(config-bdomain)# ip igmp snoopingConfiguration on port 1

Switch(config)# interface port-channel 10Switch(config-if)# service instance 10 ethernetSwitch(config-if-srv)# encapsulation dot1q 10Switch(config-if-srv)# rewrite ingress tag pop 1 symmetricSwitch(config-if-srv)# bridge-domain 30Switch(config)# interface gi0/25Switch(config-if)# channel-group 10Switch(config)# interface gi0/26Switch(config-if)# channel-group 10Configuration on port 2Switch(config)# interface gi0/1Switch(config-if)# service instance 10 ethernetSwitch(config-if-srv)# encapsulation dot1q 20 second-dot1q 30Switch(config-if-srv)# rewrite ingress pop 2 symmetricSwitch(config-if-srv)# bridge-domain 30Configuration on port 3Switch(config)# interface gi0/2Switch(config-if)# service instance 10 ethernetSwitch(config-if-srv)# encapsulation dot1q 40Switch(config-if-srv)# rewrite ingress tag pop 1 symmetricSwitch(config-if-srv)# bridge-domain 30The following example shows how to configure the receiver port, which is part of the LAG interface that isa member of the bridge domain that has IGMP snooping enabled.

Configuration on the bridge-domainSwitch(config)# bridge-domain 30Switch(config-bdomain)# ip igmp snooping


IGMP SnoopingL2 Address Aliasing Issue

Configuration on port 1Switch(config)# interface ten 0/45Switch(config-if)# service instance 10 ethernetSwitch(config-if-srv)# encapsulation dot1q 10 second-dot1q 30Switch(config-if-srv)# rewrite ingress pop 2 symmetricSwitch(config-if-srv)# bridge-domain 30Configuration port 2Switch(config)# interface port-channel 10Switch(config-if)# service instance 10 ethernetSwitch(config-if-srv)# encapsulation dot1q 10Switch(config-if-srv)# rewrite ingress tag pop 1 symmetricSwitch(config-if-srv)# bridge-domain 30Switch(config)# interface gi0/25Switch(config-if)# channel-group 10Switch(config)# interface gi0/26Switch(config-if)# channel-group 10Configuration on port 3Switch(config)# interface gi0/5Switch(config-if)# service instance 10 ethernetSwitch(config-if-srv)# encapsulation dot1q 40Switch(config-if-srv)# rewrite ingress tag pop 1 symmetricSwitch(config-if-srv)# bridge-domain 30

IGMP Statistics and CountersAn entry in a counter contains multicasting statistical information for the IGMP snooping capable Cisco ME2600X system. The equivalent IOS command to retrieve statistical information is show ip igmp snoopingcounters.

This information can be stored in the following counters:

• Tx General Queries—Number of general queries transmitted through an interface.

• Tx Group Specific Queries—Total group specific queries transmitted through an interface.

• Tx Reports—Total membership reports transmitted through an interface.

• Tx Leaves—Total leave messages transmitted through an interface.

• Rx General Queries—Total general queries received at an interface.

• Rx Group Specific Queries—Total group specific queries received at an interface.

• Rx Reports—Total membership reports received at an interface.

• Rx Leaves—Total leave messages received at an interface.

• Rx Valid Packets—Total valid IGMP packets received at an interface.

• Rx Invalid Packets—Total number of invalid IGMP packets that are received at an interface.

The following example shows the statistical information using the show ip igmp snooping counters command.Switch> show ip igmp snooping counters

packet queue maximum size: 20000packet queue current size: 0packet queue peak size: 0packet queue drop count: 0----


IGMP SnoopingIGMP Statistics and Counters

Vlan 1----

Counters of group "IGMP snooping counters "overall there are 15 countersType | Value | Ovr |Und---------------------------------------------------+------------+-----+----RX processed Query Count | 0 | |

RX processed Group Specific Query | 0 | |

RX processed Join | 787120 | |

RX processed Leave | 0 | |

RX processed Total Valid Packets | 782 | |

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 countersRX 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 | 782 | |


IGMP SnoopingIGMP Statistics and Counters

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 | |

AlarmsThe MCAST-MAC-TABLE-FULL condition is raised from IGMP snooping at Cisco ME 2600X. The CiscoME 2600X supports a maximum of 2000 multicast groups. The MCAST-MAC-TABLE-FULL condition israised when the multicast table is full and a new join request is received. This table is cleared when at leastone entry gets cleared from the multicast table after the alarm is raised.


IGMP SnoopingAlarms


IGMP SnoopingAlarms

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