- Preface
- Overview
- Using the Command-Line Interface
- Configuring the Switch Alarms
- Performing Switch Setup Configuration
- Configuring Cisco IOS Configuration Engine
- Configuring Switch Clusters
- Performing Switch Administration
- Configuring PTP
- Configuring PROFINET
- Configuring CIP
- Configuring SDM Templates
- Configuring Switch-Based Authentication
- Configuring IEEE 802.1x Port-Based Authentication
- Configuring Web-Based Authentication
- Configuring SGT Exchange Protocol over TCP (SXP) and Layer 3 Transport
- Configuring Interface Characteristics
- Configuring Smartports Macros
- Configuring VLANs
- Configuring VTP
- Configuring Voice VLAN
- Configuring STP
- Configuring MSTP
- Configuring Optional Spanning-Tree Features
- Configuring Resilient Ethernet Protocol
- Configuring Flex Links and the MAC Address-Table Move Update Feature
- Configuring DHCP
- Configuring Dynamic ARP Inspection
- Configuring IP Source Guard
- Configuring IGMP Snooping and MVR
- Configuring Port-Based Traffic Control
- Configuring SPAN and RSPAN
- Configuring LLDP, LLDP-MED, and Wired Location Service
- Configuring CDP
- Configuring UDLD
- Configuring RMON
- Configuring System Message Logging
- Configuring SNMP
- Configuring Network Security with ACLs
- Configuring Standard QoS
- Configuring Auto-QoS
- Configuring EtherChannels
- Configuring Static IP Unicast Routing
- Configuring IPv6 Host Functions
- Configuring Link State Tracking
- Configuring IPv6 MLD Snooping
- Configuring Cisco IOS IP SLAs Operations
- Troubleshooting the Cisco IOS Software
- Working with the Cisco IOS File System, Configuration Files, and Software Images
- Finding Feature Information
- Prerequisites for Configuring IPv6 MLD Snooping
- Restrictions for Configuring IPv6 MLD Snooping
- Information About Configuring IPv6 MLD Snooping
- IPv6 MLD Snooping
- MLD Messages
- MLD Queries
- Multicast Client Aging Robustness
- Multicast Router Discovery
- MLD Reports
- MLD Done Messages and Immediate-Leave
- Topology Change Notification Processing
- Default MLD Snooping Configuration
- MLD Snooping Configuration Guidelines
- Enabling or Disabling MLD Snooping
- Multicast Router Port
- MLD Immediate Leave
- MLD Snooping Queries
- IPv6 MLD Snooping
Configuring IPv6 MLD Snooping
Finding Feature Information
Your software release may not support all the features documented in this chapter. For the latest feature information and caveats, see the release notes for your platform and software release.
Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An account on Cisco.com is not required.
Prerequisites for Configuring IPv6 MLD Snooping
Restrictions for Configuring IPv6 MLD Snooping
Information About Configuring IPv6 MLD Snooping
IPv6 MLD Snooping
In IP version 4 (IPv4), Layer 2 switches can use Internet Group Management Protocol (IGMP) snooping to limit 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. In IPv6, MLD snooping performs a similar function. With MLD snooping, IPv6 multicast data is selectively forwarded to a list of ports that want to receive the data, instead of being flooded to all ports in a VLAN. This list is constructed by snooping IPv6 multicast control packets.
MLD is a protocol used by IPv6 multicast routers to discover the presence of multicast listeners (nodes that want to receive IPv6 multicast packets) on its directly attached links and to discover which multicast packets are of interest to neighboring nodes. MLD is derived from IGMP; MLD version 1 (MLDv1) is equivalent to IGMPv2 and MLD version 2 (MLDv2) is equivalent to IGMPv3. MLD is a subprotocol of Internet Control Message Protocol version 6 (ICMPv6), and MLD messages are a subset of ICMPv6 messages, identified in IPv6 packets by a preceding Next Header value of 58.
The switch supports two versions of MLD snooping:
- MLDv1 snooping detects MLDv1 control packets and sets up traffic bridging based on IPv6 destination multicast addresses.
- MLDv2 basic snooping (MBSS) uses MLDv2 control packets to set up traffic forwarding based on IPv6 destination multicast addresses.
The switch can snoop on both MLDv1 and MLDv2 protocol packets and bridge IPv6 multicast data based on destination IPv6 multicast addresses.
Note The switch does not support MLDv2 enhanced snooping (MESS), which sets up IPv6 source and destination multicast address-based forwarding.
MLD snooping can be enabled or disabled globally or per VLAN. When MLD snooping is enabled, a per-VLAN IPv6 multicast MAC address table is constructed in software and a per-VLAN IPv6 multicast address table is constructed in software and hardware. The switch then performs IPv6 multicast-address based bridging in hardware.
MLD Messages
MLDv1 supports three types of messages:
- Listener Queries are the equivalent of IGMPv2 queries and are either General Queries or Multicast-Address-Specific Queries (MASQs).
- Multicast Listener Reports are the equivalent of IGMPv2 reports.
- Multicast Listener Done messages are the equivalent of IGMPv2 leave messages.
MLDv2 supports MLDv2 queries and reports, as well as MLDv1 Report and Done messages.
Message timers and state transitions resulting from messages being sent or received are the same as those of IGMPv2 messages. MLD messages that do not have valid link-local IPv6 source addresses are ignored by MLD routers and switches.
MLD Queries
The switch sends out MLD queries, constructs an IPv6 multicast address database, and generates MLD group-specific and MLD group-and-source-specific queries in response to MLD Done messages. The switch also supports report suppression, report proxying, Immediate-Leave functionality, and static IPv6 multicast MAC-address configuration.
When MLD snooping is disabled, all MLD queries are flooded in the ingress VLAN.
When MLD snooping is enabled, received MLD queries are flooded in the ingress VLAN, and a copy of the query is sent to the CPU for processing. From the received query, MLD snooping builds the IPv6 multicast address database. It detects multicast router ports, maintains timers, sets report response time, learns the querier IP source address for the VLAN, learns the querier port in the VLAN, and maintains multicast-address aging.
Note When the IPv6 multicast router is a Catalyst 6500 switch and you are using extended VLANs (in the range 1006 to 4096), IPv6 MLD snooping must be enabled on the extended VLAN on the switch in order for the switch to receive queries on the VLAN. For normal-range VLANs (1 to 1005), it is not necessary to enable IPv6 MLD snooping on the VLAN on the switch.
When a group exists in the MLD snooping database, the switch responds to a group-specific query by sending an MLDv1 report. When the group is unknown, the group-specific query is flooded to the ingress VLAN.
When a host wants to leave a multicast group, it can send out an MLD Done message (equivalent to IGMP Leave message). When the switch receives an MLDv1 Done message, if Immediate-Leave is not enabled, the switch sends an MASQ to the port from which the message was received to determine if other devices connected to the port should remain in the multicast group.
Multicast Client Aging Robustness
You can configure port membership removal from addresses based on the number of queries. A port is removed from membership to an address only when there are no reports to the address on the port for the configured number of queries. The default number is 2.
Multicast Router Discovery
Like IGMP snooping, MLD snooping performs multicast router discovery, with these characteristics:
- Ports configured by a user never age out.
- Dynamic port learning results from MLDv1 snooping queries and IPv6 PIMv2 packets.
- If there are multiple routers on the same Layer 2 interface, MLD snooping tracks a single multicast router on the port (the router that most recently sent a router control packet).
- Dynamic multicast router port aging is based on a default timer of 5 minutes; the multicast router is deleted from the router port list if no control packet is received on the port for 5 minutes.
- IPv6 multicast router discovery only takes place when MLD snooping is enabled on the switch.
- Received IPv6 multicast router control packets are always flooded to the ingress VLAN, whether or not MLD snooping is enabled on the switch.
- After the discovery of the first IPv6 multicast router port, unknown IPv6 multicast data is forwarded only to the discovered router ports (before that time, all IPv6 multicast data is flooded to the ingress VLAN).
MLD Reports
The processing of MLDv1 join messages is essentially the same as with IGMPv2. When no IPv6 multicast routers are detected in a VLAN, reports are not processed or forwarded from the switch. When IPv6 multicast routers are detected and an MLDv1 report is received, an IPv6 multicast group address and an IPv6 multicast MAC address are entered in the VLAN MLD database. Then all IPv6 multicast traffic to the group within the VLAN is forwarded using this address. When MLD snooping is disabled, reports are flooded in the ingress VLAN.
When MLD snooping is enabled, MLD report suppression, called listener message suppression, is automatically enabled. With report suppression, the switch forwards the first MLDv1 report received by a group to IPv6 multicast routers; subsequent reports for the group are not sent to the routers. When MLD snooping is disabled, report suppression is disabled, and all MLDv1 reports are flooded to the ingress VLAN.
The switch also supports MLDv1 proxy reporting. When an MLDv1 MASQ is received, the switch responds with MLDv1 reports for the address on which the query arrived if the group exists in the switch on another port and if the port on which the query arrived is not the last member port for the address.
MLD Done Messages and Immediate-Leave
When the Immediate-Leave feature is enabled and a host sends an MLDv1 Done message (equivalent to an IGMP leave message), the port on which the Done message was received is immediately deleted from the group.You enable Immediate-Leave on VLANs and (as with IGMP snooping), you should only use the feature on VLANs where a single host is connected to the port. If the port was the last member of a group, the group is also deleted, and the leave information is forwarded to the detected IPv6 multicast routers.
When Immediate Leave is not enabled in a VLAN (which would be the case when there are multiple clients for a group on the same port) and a Done message is received on a port, an MASQ is generated on that port. The user can control when a port membership is removed for an existing address in terms of the number of MASQs. A port is removed from membership to an address when there are no MLDv1 reports to the address on the port for the configured number of queries.
The number of MASQs generated is configured by using the ipv6 mld snooping last-listener-query count global configuration command. The default number is 2.
The MASQ is sent to the IPv6 multicast address for which the Done message was sent. If there are no reports sent to the IPv6 multicast address specified in the MASQ during the switch maximum response time, the port on which the MASQ was sent is deleted from the IPv6 multicast address database. The maximum response time is the time configured by using the ipv6 mld snooping last-listener-query-interval global configuration command. If the deleted port is the last member of the multicast address, the multicast address is also deleted, and the switch sends the address leave information to all detected multicast routers.
Topology Change Notification Processing
When topology change notification (TCN) solicitation is enabled by using the ipv6 mld snooping tcn query solicit global configuration command, MLDv1 snooping sets the VLAN to flood all IPv6 multicast traffic with a configured number of MLDv1 queries before it begins sending multicast data only to selected ports. You set this value by using the ipv6 mld snooping tcn flood query count global configuration command. The default is to send two queries. The switch also generates MLDv1 global Done messages with valid link-local IPv6 source addresses when the switch becomes the STP root in the VLAN or when it is configured by the user. This is same as done in IGMP snooping.
Default MLD Snooping Configuration
MLD Snooping Configuration Guidelines
When configuring MLD snooping, consider these guidelines:
- You can configure MLD snooping characteristics at any time, but you must globally enable MLD snooping by using the ipv6 mld snooping global configuration command for the configuration to take effect.
- When the IPv6 multicast router is a switch and you are using extended VLANs (in the range 1006 to 4096), IPv6 MLD snooping must be enabled on the extended VLAN on the switch in order for the switch to receive queries on the VLAN. For normal-range VLANs (1 to 1005), it is not necessary to enable IPv6 MLD snooping on the VLAN on the switch.
- MLD snooping and IGMP snooping act independently of each other. You can enable both features at the same time on the switch.
- The maximum number of multicast entries allowed on the switch is determined by the configured SDM template.
- The maximum number of address entries allowed for the switch is 1000.
Enabling or Disabling MLD Snooping
By default, IPv6 MLD snooping is globally disabled on the switch and enabled on all VLANs. When MLD snooping is globally disabled, it is also disabled on all VLANs. When you globally enable MLD snooping, the VLAN configuration overrides the global configuration. That is, MLD snooping is enabled only on VLAN interfaces in the default state (enabled).
You can enable and disable MLD snooping on a per-VLAN basis or for a range of VLANs, but if you globally disable MLD snooping, it is disabled in all VLANs. If global snooping is enabled, you can enable or disable VLAN snooping.
Multicast Router Port
Although MLD snooping learns about router ports through MLD queries and PIMv6 queries, you can also use the command-line interface (CLI) to add a multicast router port to a VLAN. To add a multicast router port (add a static connection to a multicast router), use the ipv6 mld snooping vlan mrouter global configuration command on the switch.
MLD Immediate Leave
When you enable MLDv1 Immediate Leave, the switch immediately removes a port from a multicast group when it detects an MLD Done message on that port. You should only use the Immediate-Leave feature when there is a single receiver present on every port in the VLAN. When there are multiple clients for a multicast group on the same port, you should not enable Immediate-Leave in a VLAN.
MLD Snooping Queries
When Immediate Leave is not enabled and a port receives an MLD Done message, the switch generates MASQs on the port and sends them to the IPv6 multicast address for which the Done message was sent. You can optionally configure the number of MASQs that are sent and the length of time the switch waits for a response before deleting the port from the multicast group.
How to Configure IPv6 MLD Snooping
Note When the IPv6 multicast router is a Catalyst 6500 switch and you are using extended VLANs (in the range 1006 to 4096), IPv6 MLD snooping must be enabled on the extended VLAN on the switch in order for the switch to receive queries on the VLAN. For normal-range VLANs (1 to 1005), it is not necessary to enable IPv6 MLD snooping on the VLAN on the switch.
Enabling or Disabling MLD Snooping
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(Optional) Enables MLD snooping on the VLAN.The VLAN ID range is 1 to 1001 and 1006 to 4096. MLD snooping must be globally enabled for VLAN snooping to be enabled. |
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Configuring a Static Multicast Group
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ipv6 mld snooping vlan vlan-id static ipv6_multicast_address interface interface-id |
Statically configures a multicast group with a Layer 2 port as a member of a multicast group: |
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Configuring a Multicast Router Port
Note Static connections to multicast routers are supported only on switch ports.
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ipv6 mld snooping vlan vlan-id mrouter interface interface-id |
Specifies the multicast router VLAN ID, and specifies the interface to the multicast router. |
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Enabling MLD Immediate Leave
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Configuring MLD Snooping Queries
Disabling MLD Listener Message Suppression
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Monitoring and Maintaining IPv6 MLD Snooping
You can display MLD 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 MLD snooping.
Configuration Examples for Configuring IPv6 MLD Snooping
Statically Configure an IPv6 Multicast Group: Example
This example shows how to statically configure an IPv6 multicast group:
Adding a Multicast Router Port to a VLAN: Example
This example shows how to add a multicast router port to VLAN 200:
(config)#
ipv6 mld snooping vlan 200 mrouter interface gigabitethernet1/2
(config)#
exit
Enabling MLD Immediate Leave on a VLAN: Example
This example shows how to enable MLD Immediate Leave on VLAN 130:
Setting MLD Snooping Global Robustness: Example
This example shows how to set the MLD snooping global robustness variable to 3:
Setting MLD Snooping Last-Listener Query Parameters: Examples
This example shows how to set the MLD snooping last-listener query count for a VLAN to 3:
This example shows how to set the MLD snooping last-listener query interval (maximum response time) to 2000 (2 seconds):
Additional References
The following sections provide references related to switch administration:
Related Documents
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Standards
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No new or modified standards are supported by this feature, and support for existing standards has not been modified by this feature. |
MIBs
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To locate and download MIBs, use the Cisco MIB Locator found at the following URL: https://cfnng.cisco.com/mibs |
RFCs
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No new or modified RFCs are supported by this feature, and support for existing RFCs has not been modified by this feature. |