06-IP Multicast Configuration Guide

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09-MLD snooping configuration
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09-MLD snooping configuration 340.33 KB

Contents

Configuring MLD snooping· 1

About MLD snooping· 1

Fundamentals of MLD snooping· 1

MLD snooping ports· 1

How MLD snooping works· 3

MLD snooping proxying· 4

Protocols and standards· 5

Restrictions and guidelines: MLD snooping configuration·· 5

MLD snooping tasks at a glance· 6

Enabling the MLD snooping feature· 6

Enabling MLD snooping· 7

Enabling MLD snooping globally· 7

Enabling MLD snooping for VLANs· 7

Configuring basic MLD snooping features· 8

Specifying an MLD snooping version·· 8

Setting the maximum number of MLD snooping forwarding entries· 9

Configuring static IPv6 multicast MAC address entries· 9

Setting the MLD last listener query interval 10

Configuring MLD snooping port features· 11

Setting aging timers for dynamic ports· 11

Configuring a static member port 12

Configuring a static router port 12

Configuring a port as a simulated member host 12

Enabling fast-leave processing· 13

Disabling a port from becoming a dynamic router port 14

Configuring the MLD snooping querier 14

Enabling the MLD snooping querier 14

Enabling MLD snooping querier election·· 15

Configuring parameters for MLD general queries and responses· 15

Enabling MLD snooping proxying· 16

Configuring parameters for MLD messages· 16

Configuring source IPv6 addresses for MLD messages· 16

Setting the 802.1p priority for MLD messages· 17

Configuring MLD snooping policies· 18

Configuring an IPv6 multicast group policy· 18

Enabling IPv6 multicast source port filtering· 19

Enabling dropping unknown IPv6 multicast data· 19

Enabling MLD report suppression·· 20

Setting the maximum number of IPv6 multicast groups on a port 20

Enabling IPv6 multicast group replacement 21

Enabling host tracking· 21

Configuring an MLD snooping access control policy· 22

Setting the DSCP value for outgoing MLD protocol packets· 22

Display and maintenance commands for MLD snooping· 23

MLD snooping configuration examples· 24

Example: Configuring IPv6 group policy and simulated joining· 24

Example: Configuring static ports· 26

Example: Configuring the MLD snooping querier 29

Example: Configuring MLD snooping proxying· 31

Troubleshooting MLD snooping· 33

Layer 2 multicast forwarding cannot function·· 33

IPv6 multicast group policy does not work· 34

 


Configuring MLD snooping

About MLD snooping

MLD snooping runs on a Layer 2 device as an IPv6 multicast constraining mechanism to improve multicast forwarding efficiency. It creates Layer 2 multicast forwarding entries from MLD messages that are exchanged between the hosts and the Layer 3 device.

Fundamentals of MLD snooping

As shown in Figure 1, when MLD snooping is not enabled, the Layer 2 switch floods IPv6 multicast packets all hosts in a VLAN. When MLD snooping is enabled, the Layer 2 switch forwards multicast packets of known IPv6 multicast groups to only the receivers.

Figure 1 Multicast packet transmission processes without and with MLD snooping

 

MLD snooping ports

As shown in Figure 2, MLD snooping runs on Switch A and Switch B, and Host A and Host C are receiver hosts in an IPv6 multicast group. MLD snooping ports are divided into member ports and router ports.

Figure 2 MLD snooping ports

 

Router ports

On an MLD snooping Layer 2 device, the ports toward Layer 3 multicast devices are called router ports. In Figure 2, Port A1 of Switch A and Port B1 of Switch B are router ports.

Router ports contain the following types:

·          Dynamic router port—When a port receives an MLD general query whose source address is not 0::0 or receives an IPv6 PIM hello message, the port is added into the dynamic router port list. At the same time, an aging timer is started for the port. If the port receives either of the messages before the timer expires, the timer is reset. If the port does not receive either of the messages when the timer expires, the port is removed from the dynamic router port list.

·          Static router port—When a port is statically configured as a router port, it is added into the static router port list. The static router port does not age out, and it can be deleted only manually.

Do not confuse the "router port" in MLD snooping with the "routed interface" commonly known as the "Layer 3 interface." The router port in MLD snooping is a Layer 2 interface.

Member ports

On an MLD snooping Layer 2 device, the ports toward receiver hosts are called member ports. In Figure 2, Port A2 and Port A3 of Switch A and Port B2 of Switch B are member ports.

Member ports contain the following types:

·          Dynamic member port—When a port receives an MLD report, it is added to the associated dynamic MLD snooping forwarding entry as an outgoing interface. At the same time, an aging timer is started for the port. If the port receives an MLD report before the timer expires, the timer is reset. If the port does not receive an MLD report when the timer expires, the port is removed from the associated dynamic forwarding entry.

·          Static member port—When a port is statically configured as a member port, it is added to the associated static MLD snooping forwarding entry as an outgoing interface. The static member port does not age out, and it can be deleted only manually.

Unless otherwise specified, router ports and member ports in this document include both static and dynamic router ports and member ports.

How MLD snooping works

The ports in this section are dynamic ports. For information about how to configure and remove static ports, see "Configuring a static member port" and "Configuring a static router port."

MLD messages include general query, MLD report, and done message. An MLD snooping-enabled Layer 2 device performs differently depending on the MLD message types.

General query

The MLD querier periodically sends MLD general queries to all hosts and devices on the local subnet to check for the existence of IPv6 multicast group members.

After receiving an MLD general query, the Layer 2 device forwards the query to all ports in the VLAN except the receiving port. The Layer 2 device also performs one of the following actions:

·          If the receiving port is a dynamic router port in the dynamic router port list, the Layer 2 device restarts the aging timer for the router port.

·          If the receiving port does not exist in the dynamic router port list, the Layer 2 device adds the port to the dynamic router port list. It also starts an aging timer for the port.

MLD report

A host sends an MLD report to the MLD querier for the following purposes:

·          Responds to queries if the host is an IPv6 multicast group member.

·          Applies for an IPv6 multicast group membership.

After receiving an MLD report from a host, the Layer 2 device forwards the report through all the router ports in the VLAN. It also resolves the IPv6 address of the reported IPv6 multicast group, and looks up the forwarding table for a matching entry as follows:

·          If no match is found, the Layer 2 device creates a forwarding entry for the group with the receiving port an outgoing interface. It also marks the receiving port as a dynamic member port and starts an aging timer for the port.

·          If a match is found but the matching forwarding entry does not contain the receiving port, the Layer 2 device adds the receiving port to the outgoing interface list. It also marks the port as a dynamic member port to the forwarding entry and starts an aging timer for the port.

·          If a match is found and the matching forwarding entry contains the receiving port, the Layer 2 device restarts the aging timer for the port.

 

 

NOTE:

A Layer 2 device does not forward an MLD report through a non-router port because of the host MLD report suppression mechanism. If a non-router port has member host attached, the member hosts suppress their MLD reports upon receiving MLD reports forwarded by the non-router port. The Layer 2 device cannot know the existence of the member hosts attached to the non-router port. For more information about the MLD report suppression mechanism, see "Configuring MLD."

 

Done message

When a host leaves an IPv6 multicast group, the host sends an MLD done message to the Layer 3 devices. When the Layer 2 device receives the MLD done message on a dynamic member port, the Layer 2 device first examines whether a forwarding entry matches the IPv6 multicast group address in the message.

·          If no match is found, the Layer 2 device discards the MLD done message.

·          If a match is found but the receiving port is not an outgoing interface in the forwarding entry, the Layer 2 device discards the MLD done message.

·          If a match is found and the receiving port is not the only outgoing interface in the forwarding entry, the Layer 2 device performs the following actions:

¡  Discards the MLD done message.

¡  Sends an MLD multicast-address-specific query to identify whether the group has active listeners attached to the receiving port.

¡  Sets the aging timer for the receiving port to twice the MLD last listener query interval.

·          If a match is found and the receiving port is the only outgoing interface in the forwarding entry, the Layer 2 device performs the following actions:

¡  Forwards the MLD done message to all router ports in the VLAN.

¡  Sends an MLD multicast-address-specific query to identify whether the group has active listeners attached to the receiving port.

¡  Sets the aging timer for the receiving port to twice the MLD last listener query interval.

After receiving the MLD done message on a port, the MLD querier resolves the IPv6 multicast group address in the message. Then, it sends an MLD multicast-address-specific query to the IPv6 multicast group through the receiving port.

After receiving the MLD multicast-address-specific query, the Layer 2 device forwards the query through all router ports and member ports of the group in the VLAN. Then, it waits for the responding MLD report from the directly connected hosts. For the dynamic member port that received the done message, the Layer 2 device also performs one of the following actions:

·          If the port receives an MLD report before the aging timer expires, the Layer 2 device resets the aging timer for the port.

·          If the port does not receive any MLD report messages when the aging timer expires, the Layer 2 device removes the port from the forwarding entry for the IPv6 multicast group.

MLD snooping proxying

As shown in Figure 3, to reduce the number of MLD report and done messages received by the upstream device, you can enable MLD snooping proxying on the edge device. With MLD snooping proxying enabled, the edge device acts as a host for the upstream MLD snooping querier to send MLD report and done messages to Device A. The host MLD report suppression mechanism on the edge device does not take effect. For more information about the MLD report suppression mechanism, see "Configuring MLD."

Figure 3 MLD snooping proxying

 

The MLD snooping proxy device processes different MLD messages as follows:

·          General query.

After receiving an MLD general query, the device forwards the query to all ports in the VLAN except the receiving port. The device also generates an MLD report based on the local membership information and sends the report to all router ports.

·          Multicast-address-specific query or multicast-address-and-source-specific query.

After receiving an MLD multicast-address-specific query or multicast-address-and-source-specific query, the device forwards the query to all ports in the VLAN except the receiving port. If the forwarding entry has a member port, the device sends a response to all router ports in the VLAN.

·          Report.

After receiving an MLD report from a host, the device looks up the forwarding table for a matching entry as follows:

¡  If a match is found and the matching forwarding entry contains the receiving port, the device resets the aging timer for the port.

¡  If a match is found but the matching forwarding entry does not contain the receiving port, the device adds the receiving port to the outgoing interface list. It also marks the receiving port as a dynamic member port and starts an aging timer for the port.

¡  If no match is found, the device creates a forwarding entry with the receiving port as an outgoing interface. It also marks the receiving port as a dynamic member port and starts an aging timer for the port. Then it sends the report to all router ports.

·          Done message.

After receiving the MLD done message on a port, the device sends an MLD multicast-address-specific query through the receiving port. The device sends the MLD done message to all router ports only when the last member port is removed from the forwarding entry.

Protocols and standards

RFC 4541, Considerations for Internet Group Management Protocol (IGMP) and Multicast Listener Discovery (MLD) Snooping Switches

Restrictions and guidelines: MLD snooping configuration

For MLD reports received from secondary VLANs, the relevant MLD snooping forwarding entries are maintained by the primary VLAN. Therefore, you need to enable MLD snooping only for the primary VLAN. The configuration made in secondary VLANs will not take effect. For more information about primary VLANs and secondary VLANs, see Layer 2—LAN Switching Configuration Guide.

The MLD snooping configurations made on Layer 2 aggregate interfaces do not interfere with the configurations made on member ports. In addition, the configurations made on Layer 2 aggregate interfaces do not take part in aggregation calculations. The configuration made on a member port of the aggregate group takes effect after the port leaves the aggregate group.

Some features can be configured for a VLAN in VLAN view or for multiple VLANs in MLD-snooping view. The VLAN-specific configuration and the configuration made in MLD-snooping view have the same priority, and the most recent configuration takes effect.

Some features can be configured for a VLAN in VLAN view or globally for all VLANs in MLD-snooping view. The VLAN-specific configuration takes priority over the global configuration.

Some features can be configured for an interface in interface view or for all interfaces of the specified VLANs in MLD-snooping view. The interface-specific configuration takes priority over the configuration made in MLD-snooping view.

MLD snooping tasks at a glance

To configure MLD snooping for VLANs, perform the following tasks:

1.        Enabling the MLD snooping feature

2.        Enabling MLD snooping

Choose the following tasks as needed:

¡  Enabling MLD snooping globally

¡  Enabling MLD snooping for VLANs

3.        (Optional.) Configuring basic MLD snooping features

¡  Specifying an MLD snooping version

¡  Setting the maximum number of MLD snooping forwarding entries

¡  Configuring static IPv6 multicast MAC address entries

¡  Setting the MLD last listener query interval

4.        (Optional.) Configuring MLD snooping port features

¡  Setting aging timers for dynamic ports

¡  Configuring a static member port

¡  Configuring a static router port

¡  Configuring a port as a simulated member host

¡  Enabling fast-leave processing

¡  Disabling a port from becoming a dynamic router port

5.        (Optional.) Configuring the MLD snooping querier

¡  Enabling the MLD snooping querier

¡  Enabling MLD snooping querier election

¡  Configuring parameters for MLD general queries and responses

6.        (Optional.) Enabling MLD snooping proxying

7.        (Optional.) Configuring parameters for MLD messages

¡  Configuring source IPv6 addresses for MLD messages

¡  Setting the 802.1p priority for MLD messages

8.        (Optional.) Configuring MLD snooping policies

¡  Configuring an IPv6 multicast group policy

¡  Enabling IPv6 multicast source port filtering

¡  Enabling dropping unknown IPv6 multicast data

¡  Enabling MLD report suppression

¡  Setting the maximum number of IPv6 multicast groups on a port

¡  Enabling IPv6 multicast group replacement

¡  Enabling host tracking

¡  Configuring an MLD snooping access control policy

9.        (Optional.) Setting the DSCP value for outgoing MLD protocol packets

Enabling the MLD snooping feature

About enabling the MLD snooping feature

You must enable the MLD snooping feature before you configure other MLD snooping features.

Procedure

1.        Enter system view.

system-view

2.        Enable the MLD snooping feature and enter MLD-snooping view.

mld-snooping

By default, the MLD snooping feature is disabled.

Enabling MLD snooping

Enabling MLD snooping globally

About enabling MLD snooping globally

After you enable MLD snooping globally, MLD snooping is enabled for all VLANs. You can disable MLD snooping for a VLAN when MLD snooping is globally enabled.

Restrictions and guidelines

To configure other MLD snooping features for VLANs, you must enable MLD snooping for the specific VLANs even though MLD snooping is enabled globally.

The VLAN-specific MLD snooping configuration takes priority over the global MLD snooping configuration. For example, if you enable MLD snooping globally and then use the mld-snooping disable command to disable MLD snooping for a VLAN, MLD snooping is disabled in the VLAN.

Procedure

1.        Enter system view.

system-view

2.        Enter MLD-snooping view.

mld-snooping

3.        Enable MLD snooping globally.

global-enable

By default, MLD snooping is disabled globally.

4.        (Optional.) Disable MLD snooping for a VLAN.

a.    Return to system view.

quit

b.    Enter VLAN view.

vlan vlan-id

c.    Disable MLD snooping for the VLAN.

mld-snooping disable

By default, the MLD snooping status in a VLAN is consistent with the global MLD snooping status.

Enabling MLD snooping for VLANs

Restrictions and guidelines

You can enable MLD snooping for multiple VLANs by using the enable vlan command in MLD-snooping view or for a VLAN by using the mld-snooping enable command in VLAN view. The configuration in VLAN view has the same priority as the configuration in MLD-snooping view.

MLD snooping configuration in a VLAN takes effect only on the member ports in the VLAN.

Enabling MLD snooping for multiple VLANs

1.        Enter system view.

system-view

2.        Enter MLD-snooping view.

mld-snooping

3.        Enable MLD snooping for multiple VLANs.

enable vlan vlan-list

By default, the MLD snooping status in a VLAN is consistent with the global MLD snooping status.

Enabling MLD snooping for a VLAN

1.        Enter system view.

system-view

2.        Enter VLAN view.

vlan vlan-id

3.        Enable MLD snooping for the VLAN.

mld-snooping enable

By default, the MLD snooping status in a VLAN is consistent with the global MLD snooping status.

Configuring basic MLD snooping features

Specifying an MLD snooping version

About MLD snooping versions

Different MLD snooping versions can process different versions of MLD messages:

·          MLDv1 snooping can process MLDv1 messages and MLDv2 queries, but it floods MLDv2 reports in the VLAN instead of processing them.

·          MLDv2 snooping can process MLDv1 and MLDv2 messages.

Restrictions and guidelines

If you change the version of MLD snooping from 2 to 1, the system performs the following actions:

·          Clears all MLD snooping forwarding entries that are dynamically created.

·          Keeps static MLDv2 snooping forwarding entries (*, G).

·          Clears static MLDv2 snooping forwarding entries (S, G), which will be restored when MLD snooping is switched back to MLDv2 snooping.

For more information about static MLD snooping forwarding entries, see "Configuring a static member port."

Specifying an MLD snooping version for multiple VLANs

1.        Enter system view.

system-view

2.        Enter MLD-snooping view.

mld-snooping

3.        Specify an MLD snooping version for multiple VLANs.

version version-number vlan vlan-list

By default, the MLD snooping version for a VLAN is 1.

Specifying an MLD snooping version for a VLAN

1.        Enter system view.

system-view

2.        Enter VLAN view.

vlan vlan-id

3.        Specify an MLD snooping version for the VLAN.

mld-snooping version version-number

By default, the MLD snooping version for a VLAN is 1.

Setting the maximum number of MLD snooping forwarding entries

About setting the maximum number of MLD snooping forwarding entries

You can modify the maximum number of MLD snooping forwarding entries, including dynamic entries and static entries. When the number of forwarding entries on the device reaches the upper limit, the device does not automatically remove any existing entries. To allow new entries to be created, remove some entries manually.

Procedure

1.        Enter system view.

system-view

2.        Enter MLD-snooping view.

mld-snooping

3.        Set the maximum number of MLD snooping forwarding entries.

entry-limit limit

By default, the maximum number of MLD snooping forwarding entries is 4294967295.

Configuring static IPv6 multicast MAC address entries

About static IPv6 multicast MAC address entries

In Layer 2 IPv6 multicast, IPv6 multicast MAC address entries can be dynamically created through Layer 2 multicast protocols (such as MLD snooping). You can also manually configure static IPv6 multicast MAC address entries by binding IPv6 multicast MAC addresses and ports to control the destination ports of the IPv6 multicast data.

Restrictions and guidelines

You must specify an unused multicast MAC address when configuring a static IPv6 multicast MAC address entry. A multicast MAC address is the MAC address in which the least significant bit of the most significant octet is 1.

Configuring a static IPv6 multicast MAC address entry in system view

1.        Enter system view.

system-view

2.        Configure a static IPv6 multicast MAC address entry.

mac-address multicast mac-address interface interface-list vlan vlan-id

Configuring a static IPv6 multicast MAC address entry in interface view

1.        Enter system view.

system-view

2.        Enter Layer 2 interface view.

¡  Enter Layer 2 Ethernet interface view.

interface interface-type interface-number

¡  Enter Layer 2 aggregate interface view.

interface bridge-aggregation interface-number

3.        Configure a static IPv6 multicast MAC address entry.

mac-address multicast mac-address vlan vlan-id

Setting the MLD last listener query interval

About the MLD last listener query interval

A receiver host starts a report delay timer for an IPv6 multicast group when it receives an MLD multicast-address-specific query for the group. This timer is set to a random value in the range of 0 to the maximum response time advertised in the query. When the timer value decreases to 0, the host sends an MLD report to the group.

The MLD last listener query interval defines the maximum response time advertised in MLD multicast-address-specific queries. Set an appropriate value for the MLD last listener query interval to speed up hosts' responses to MLD multicast-address-specific queries and avoid MLD report traffic bursts.

Setting the MLD last listener query interval globally

1.        Enter system view.

system-view

2.        Enter MLD-snooping view.

mld-snooping

3.        Set the MLD last listener query interval globally.

last-listener-query-interval interval

By default, the MLD last listener query interval is 1 second.

Setting the MLD last listener query interval for a VLAN

1.        Enter system view.

system-view

2.        Enter VLAN view.

vlan vlan-id

3.        Set the MLD last listener query interval for the VLAN

mld-snooping last-listener-query-interval interval

By default, the MLD last listener query interval is 1 second for a VLAN.

Configuring MLD snooping port features

Setting aging timers for dynamic ports

About aging timers for dynamic ports

A dynamic router port is removed from the dynamic router port list if it does not receive an MLD general query or IPv6 PIM hello message when its aging timer expires.

A dynamic member port is removed from the dynamic member port if it does not receive an MLD report when its aging timer expires.

Restrictions and guidelines

Set an appropriate value for the aging timers of dynamic ports based on the actual network requirement. For example, if the memberships of IPv6 multicast groups frequently change, set a relatively small value for the aging timer of the dynamic member ports.

If a dynamic router port receives an IPv6 PIMv2 hello message, the aging timer for the port is specified by the hello message. In this case, the mld-snooping router-aging-time command does not take effect on the port.

MLD multicast-address-specific queries originated by the Layer 2 device trigger the adjustment of aging timers of dynamic member ports. If a dynamic member port receives such a query, its aging timer is set to twice the MLD last listener query interval. For more information about setting the MLD last listener query interval on the Layer 2 device, see "Setting the MLD last listener query interval."

Setting the aging timers for dynamic ports globally

1.        Enter system view.

system-view

2.        Enter MLD-snooping view.

mld-snooping

3.        Set the aging timer for dynamic router ports globally.

router-aging-time seconds

By default, the aging timer for dynamic router ports is 260 seconds.

4.        Set the aging timer for dynamic member ports globally.

host-aging-time seconds

By default, the aging timer for dynamic member ports is 260 seconds.

Setting the aging timers for dynamic ports in a VLAN

1.        Enter system view.

system-view

2.        Enter VLAN view.

vlan vlan-id

3.        Set the aging timer for dynamic router ports in the VLAN.

mld-snooping router-aging-time seconds

By default, the aging timer for dynamic router ports is 260 seconds for a VLAN.

4.        Set the aging timer for dynamic member ports in the VLAN.

mld-snooping host-aging-time seconds

By default, the aging timer for dynamic member ports is 260 seconds for a VLAN.

Configuring a static member port

About static member ports

You can configure a port as a static member port for an IPv6 multicast group so that all hosts attached to the port can always receive IPv6 multicast data for the group. The static member port does not respond to MLD queries. When you complete or cancel this configuration, the port does not send an unsolicited report or done message.

Procedure

1.        Enter system view.

system-view

2.        Enter Layer 2 interface view.

¡  Enter Layer 2 Ethernet interface view.

interface interface-type interface-number

¡  Enter Layer 2 aggregate interface view.

interface bridge-aggregation interface-number

3.        Configure the port as a static member port.

mld-snooping static-group ipv6-group-address [ source-ip ipv6-source-address ] vlan vlan-id

By default, a port is not a static member port.

Configuring a static router port

About static router ports

You can configure a port as a static router port for an IPv6 multicast group so that all IPv6 multicast data for the group received on the port will be forwarded.

Procedure

1.        Enter system view.

system-view

2.        Enter Layer 2 interface view.

¡  Enter Layer 2 Ethernet interface view.

interface interface-type interface-number

¡  Enter Layer 2 aggregate interface view.

interface bridge-aggregation interface-number

3.        Configure the port as a static router port.

mld-snooping static-router-port vlan vlan-id

By default, a port is not a static router port.

Configuring a port as a simulated member host

About simulated member hosts

When a port is configured as a simulated member host, it is equivalent to an independent host in the following ways:

·          It sends an unsolicited MLD report when you complete the configuration.

·          It responds to MLD general queries with MLD reports.

·          It sends an MLD done message when you remove the configuration.

The version of MLD running on the simulated member host is the same as the version of MLD snooping running on the port. The port ages out in the same ways as a dynamic member port.

Procedure

1.        Enter system view.

system-view

2.        Enter Layer 2 interface view.

¡  Enter Layer 2 Ethernet interface view.

interface interface-type interface-number

¡  Enter Layer 2 aggregate interface view.

interface bridge-aggregation interface-number

3.        Configure the port as a simulated member host.

mld-snooping host-join ipv6-group-address [ source-ip ipv6-source-address ] vlan vlan-id

By default, the port is not a simulated member host.

Enabling fast-leave processing

About fast-leave processing

This feature enables the Layer 2 device to immediately remove a port from the forwarding entry for an IPv6 multicast group when the port receives a done message. The device no longer sends or forwards MLD multicast-address-specific queries for the group to the port.

Restrictions and guidelines

Do not enable fast-leave processing on a port that has multiple receiver hosts attached in a VLAN. If you do so, the remaining receivers cannot receive IPv6 multicast data for a group after a receiver leaves the group.

Enabling fast-leave processing globally

1.        Enter system view.

system-view

2.        Enter MLD-snooping view.

mld-snooping

3.        Enable fast-leave processing globally.

fast-leave [ vlan vlan-list ]

By default, fast-leave processing is disabled globally.

Enabling fast-leave processing on a port

1.        Enter system view.

system-view

2.        Enter Layer 2 interface view.

¡  Enter Layer 2 Ethernet interface view.

interface interface-type interface-number

¡  Enter Layer 2 aggregate interface view.

interface bridge-aggregation interface-number

3.        Enable fast-leave processing on the port.

mld-snooping fast-leave [ vlan vlan-list ]

By default, fast-leave processing is disabled on a port.

Disabling a port from becoming a dynamic router port

About disabling a port from becoming a dynamic router port

A receiver host might send MLD general queries or IPv6 PIM hello messages for testing purposes. On the Layer 2 device, the port that receives either of the messages becomes a dynamic router port. Before the aging timer for the port expires, the following problems might occur:

·          All IPv6 multicast data for the VLAN to which the port belongs flows to the port. Then, the port forwards the data to attached receiver hosts. The receiver hosts will receive IPv6 multicast data that it does not expect.

·          The port forwards the MLD general queries or IPv6 PIM hello messages to its upstream Layer 3 devices. These messages might affect the multicast routing protocol state (such as the MLD querier or DR election) on the Layer 3 devices. This might further cause network interruption.

To solve these problems, you can disable the port from becoming a dynamic router port when receiving either of the messages. This also improves network security and the control over receiver hosts.

Restrictions and guidelines

This configuration and the static router port configuration do not interfere with each other.

Procedure

1.        Enter system view.

system-view

2.        Enter Layer 2 interface view.

¡  Enter Layer 2 Ethernet interface view.

interface interface-type interface-number

¡  Enter Layer 2 aggregate interface view.

interface bridge-aggregation interface-number

3.        Disable the port from becoming a dynamic router port.

mld-snooping router-port-deny [ vlan vlan-list ]

By default, a port is allowed to become a dynamic router port.

Configuring the MLD snooping querier

Enabling the MLD snooping querier

About the MLD snooping querier

This feature enables the Layer 2 device to periodically send MLD general queries to establish and maintain multicast forwarding entries at the data link Layer. You can configure an MLD snooping querier on a network without Layer 3 multicast devices.

Restrictions and guidelines

Do not enable the MLD snooping querier on an IPv6 multicast network that runs MLD. An MLD snooping querier does not participate in MLD querier elections. However, it might affect MLD querier elections if it sends MLD general queries with a low source IPv6 address. For more information about MLD queries, see "Configuring MLD."

Enabling the MLD snooping querier for a VLAN

1.        Enter system view.

system-view

2.        Enter VLAN view.

vlan vlan-id

3.        Enable the MLD snooping querier for the VLAN.

mld-snooping querier

By default, the MLD snooping querier is disabled for a VLAN.

Enabling MLD snooping querier election

About MLD snooping querier election

To avoid traffic interruption caused by the failure of a single querier in a VLAN, configure multiple queriers in the VLAN and enable querier election. When the elected querier fails, the device starts a new querier election to ensure multicast forwarding. The mechanism for MLD snooping querier election is the same as that for MLD querier election. For more information about MLD querier election, see "Configuring MLD."

Prerequisites

Before you enable MLD snooping querier election, you must complete the following tasks:

·          Enable the MLD snooping querier for a VLAN. For more information about enabling the MLD snooping querier, see "Enabling the MLD snooping querier."

·          Configure the source IPv6 address for MLD general queries as an IPv6 address different from :: and the local querier IPv6 address. An MLD snooping querier performs querier election only if the source IPv6 address of a received MLD general query is not :: or its own IPv6 address.

·          Make sure the candidate MLD snooping queriers run the same MLD snooping version. To specify the MLD snooping version, use the mld-snooping version command.

Enabling MLD snooping querier election for a VLAN

1.        Enter system view.

system-view

2.        Enter VLAN view.

vlan vlan-id

3.        Enable MLD snooping querier election for the VLAN.

mld-snooping querier-election

By default, MLD snooping querier election is disabled for a VLAN.

Configuring parameters for MLD general queries and responses

About parameters for MLD general queries and responses

You can modify the MLD general query interval based on the actual network conditions.

A receiver host starts a report delay timer for each IPv6 multicast group that it has joined when it receives an MLD general query. This timer is set to a random value in the range of 0 to the maximum response time advertised in the query. When the timer value decreases to 0, the host sends an MLD report to the corresponding IPv6 multicast group.

Set an appropriate value for the maximum response time for MLD general queries to speed up hosts' responses to MLD general queries and avoid MLD report traffic bursts.

Restrictions and guidelines

To avoid mistakenly deleting IPv6 multicast group members, make sure the MLD general query interval is greater than the maximum response time for MLD general queries.

Configuring parameters for MLD general queries and responses globally

1.        Enter system view.

system-view

2.        Enter MLD-snooping view.

mld-snooping

3.        Set the maximum response time for MLD general queries.

max-response-time seconds

By default, the maximum response time for MLD general queries is 10 seconds.

Configuring parameters for MLD general queries and responses for a VLAN

1.        Enter system view.

system-view

2.        Enter VLAN view.

vlan vlan-id

3.        Set the MLD general query interval in the VLAN.

mld-snooping query-interval interval

By default, the MLD general query interval for a VLAN is 125 seconds.

4.        Set the maximum response time for MLD general queries in the VLAN.

mld-snooping max-response-time seconds

By default, the maximum response time for MLD general queries for a VLAN is 10 seconds.

Enabling MLD snooping proxying

1.        Enter system view.

system-view

2.        Enter VLAN view.

vlan vlan-id

3.        Enable MLD snooping proxying for the VLAN.

mld-snooping proxy enable

By default, MLD snooping proxying is disabled for a VLAN.

Configuring parameters for MLD messages

Configuring source IPv6 addresses for MLD messages

About configuring source IPv6 addresses for MLD messages

You can change the source IPv6 address of the MLD queries sent by an MLD snooping querier. This configuration might affect MLD querier election within the subnet.

You can also change the source IPv6 address of MLD reports or done messages sent by a simulated member host or an MLD snooping proxy.

Configuring the source IPv6 addresses for MLD messages for a VLAN

1.        Enter system view.

system-view

2.        Enter VLAN view.

vlan vlan-id

3.        Configure the source IPv6 address for MLD general queries.

mld-snooping general-query source-ip ipv6-address

By default, the source IPv6 address of MLD general queries is the IPv6 link-local address of the current VLAN interface. If the current VLAN interface does not have an IPv6 link-local address, the source IPv6 address is FE80::02FF:FFFF:FE00:0001.

4.        Configure the source IPv6 address for MLD multicast-address-specific queries.

mld-snooping special-query source-ip ipv6-address

By default, the source IPv6 address of MLD multicast-address-specific queries is one of the following:

¡  The source address of MLD general queries if the MLD snooping querier of the VLAN has received MLD general queries.

¡  The IPv6 link-local address of the current VLAN interface if the MLD snooping querier does not receive an MLD general query.

¡  FE80::02FF:FFFF:FE00:0001 if the MLD snooping querier does not receive an MLD general query and the current VLAN interface does not have an IPv6 link-local address.

5.        Configure the source IPv6 address for MLD reports.

mld-snooping report source-ip ipv6-address

By default, the source IPv6 address of MLD reports is the IPv6 link-local address of the current VLAN interface. If the current VLAN interface does not have an IPv6 link-local address, the source IPv6 address is FE80::02FF:FFFF:FE00:0001.

6.        Configure the source IPv6 address for MLD done messages.

mld-snooping done source-ip ipv6-address

By default, the source IPv6 address of MLD done messages is the IPv6 link-local address of the current VLAN interface. If the current VLAN interface does not have an IPv6 link-local address, the source IPv6 address is FE80::02FF:FFFF:FE00:0001.

Setting the 802.1p priority for MLD messages

About the 802.1p priority for MLD messages

When congestion occurs on outgoing ports of the Layer 2 device, it forwards MLD messages in their 802.1p priority order, from highest to lowest. You can assign a higher 802.1p priority to MLD messages that are created or forwarded by the device.

Setting the 802.1p priority for MLD messages globally

1.        Enter system view.

system-view

2.        Enter MLD-snooping view.

mld-snooping

3.        Set the 802.1p priority for MLD messages globally.

dot1p-priority priority

By default, the global 802.1p priority is 6 for MLD messages.

Setting the 802.1p priority for MLD messages for a VLAN

1.        Enter system view.

system-view

2.        Enter VLAN view.

vlan vlan-id

3.        Set the 802.1p priority for MLD messages in the VLAN.

mld-snooping dot1p-priority priority

By default, the 802.1p priority is 6 for MLD messages in a VLAN.

Configuring MLD snooping policies

Configuring an IPv6 multicast group policy

About IPv6 multicast group policies

This feature enables the Layer 2 device to filter MLD reports by using an ACL that specifies the IPv6 multicast groups and the optional sources. It is used to control the IPv6 multicast groups that receiver hosts can join. This configuration takes effect on the IPv6 multicast groups that ports join dynamically.

In an IPv6 multicast application, a host sends an unsolicited MLD report when a user requests an IPv6 multicast program. The Layer 2 device uses the IPv6 multicast group policy to filter the MLD report. The host can join the IPv6 multicast group only if the MLD report is permitted by the IPv6 multicast group policy.

Configuring an IPv6 multicast group policy globally

1.        Enter system view.

system-view

2.        Enter MLD-snooping view.

mld-snooping

3.        Configure an IPv6 multicast group policy globally.

group-policy ipv6-acl-number [ vlan vlan-list ]

By default, no IPv6 multicast group policies exist. Hosts can join any IPv6 multicast groups.

Configuring an IPv6 multicast group policy on a port

1.        Enter system view.

system-view

2.        Enter Layer 2 interface view.

¡  Enter Layer 2 Ethernet interface view.

interface interface-type interface-number

¡  Enter Layer 2 aggregate interface view.

interface bridge-aggregation interface-number

3.        Configure an IPv6 multicast group policy on the port.

mld-snooping group-policy ipv6-acl-number [ vlan vlan-list ]

By default, no IPv6 multicast group policies exist on a port. Hosts attached to the port can join any IPv6 multicast groups.

Enabling IPv6 multicast source port filtering

About IPv6 multicast source port filtering

This feature enables the Layer 2 device to discard all IPv6 multicast data packets and to accept IPv6 multicast protocol packets. You can enable this feature on ports that connect to only IPv6 multicast receivers.

The configuration made in MLD-snooping view has the same priority over the interface-specific configuration.

Restrictions and guidelines

When IPv6 multicast source port filtering is enabled, the device automatically enables IPv4 multicast source port filtering.

The configuration made in MLD-snooping view has the same priority as the interface-specific configuration, and the most recent configuration takes effect.

Enabling IPv6 multicast source port filtering in MLD-snooping view

1.        Enter system view.

system-view

2.        Enter MLD-snooping view.

mld-snooping

3.        Enable IPv6 multicast source port filtering globally.

source-deny port interface-list

By default, IPv6 multicast source port filtering is disabled globally.

Enabling IPv6 multicast source port filtering in interface view

1.        Enter system view.

system-view

2.        Enter Layer 2 Ethernet interface view.

interface interface-type interface-number

3.        Enable IPv6 multicast source port filtering on the port.

mld-snooping source-deny

By default, IPv6 multicast source port filtering is disabled on a port.

Enabling dropping unknown IPv6 multicast data

About dropping unknown IPv6 multicast data

Unknown IPv6 multicast data refers to IPv6 multicast data for which no forwarding entries exist in the MLD snooping forwarding table. This feature enables the device to forward unknown IPv6 multicast data only to the router port. If the device does not have a router port, unknown IPv6 multicast data will be dropped.

If you do not enable this feature, the unknown IPv6 multicast data is flooded in the VLAN to which the data belongs.

Restrictions and guidelines

When dropping unknown IPv6 multicast data is enabled, the device also drops unknown IPv4 multicast data.

When dropping unknown IPv6 multicast data is enabled, the device still forwards unknown IPv6 multicast data out of router ports (except the receiving router port).

Enabling dropping unknown IPv6 multicast data for a VLAN

1.        Enter system view.

system-view

2.        Enter VLAN view.

vlan vlan-id

3.        Enable dropping unknown IPv6 multicast data for the VLAN.

mld-snooping drop-unknown

By default, dropping unknown IPv6 multicast data is disabled. Unknown IPv6 multicast data is flooded.

Enabling MLD report suppression

About MLD report suppression

This feature enables the Layer 2 device to forward only the first MLD report for an IPv6 multicast group to its directly connected Layer 3 device. Other reports for the same group in the same query interval are discarded. Use this feature to reduce the multicast traffic.

Procedure

1.        Enter system view.

system-view

2.        Enter MLD-snooping view.

mld-snooping

3.        Enable MLD report suppression.

report-aggregation

By default, MLD report suppression is enabled.

Setting the maximum number of IPv6 multicast groups on a port

About setting the maximum number of IPv6 multicast groups on a port

You can set the maximum number of IPv6 multicast groups on a port to regulate the port traffic. This configuration takes effect only on the IPv6 multicast groups that the port joins dynamically.

If the number of IPv6 multicast groups on a port exceeds the limit, the system removes all the forwarding entries related to that port. In this case, the receiver hosts attached to that port can join IPv6 multicast groups again before the number of IPv6 multicast groups on the port reaches the limit. When the number of IPv6 multicast groups on the port reaches the limit, the port automatically drops MLD reports for new IPv6 multicast groups.

Procedure

1.        Enter system view.

system-view

2.        Enter Layer 2 interface view.

¡  Enter Layer 2 Ethernet interface view.

interface interface-type interface-number

¡  Enter Layer 2 aggregate interface view.

interface bridge-aggregation interface-number

3.        Set the maximum number of IPv6 multicast groups on the port.

mld-snooping group-limit limit [ vlan vlan-list ]

By default, no limit is placed on the maximum number of IPv6 multicast groups on a port.

Enabling IPv6 multicast group replacement

About IPv6 multicast group replacement

When IPv6 multicast group replacement is enabled, the port does not drop MLD reports for new groups if the number of multicast groups on the port reaches the upper limit. Instead, the port leaves an IPv6 multicast group that has the lowest IPv6 address and joins the new group contained in the MLD report. The IPv6 multicast group replacement feature is typically used in the channel switching application.

Restrictions and guidelines

This feature takes effect only on the multicast groups that the port joins dynamically.

This feature does not take effect if the following conditions exist:

·          The number of the MLD snooping forwarding entries on the device reaches the upper limit.

·          The IPv6 multicast group that the port newly joins is not included in the multicast group list maintained by the device.

Enabling IPv6 multicast group replacement globally

1.        Enter system view.

system-view

2.        Enter MLD-snooping view.

mld-snooping

3.        Enable IPv6 multicast group replacement globally.

overflow-replace [ vlan vlan-list ]

By default, IPv6 multicast group replacement is disabled globally.

Enabling IPv6 multicast group replacement on a port

1.        Enter system view.

system-view

2.        Enter Layer 2 interface view.

¡  Enter Layer 2 Ethernet interface view.

interface interface-type interface-number

¡  Enter Layer 2 aggregate interface view.

interface bridge-aggregation interface-number

3.        Enable IPv6 multicast group replacement on the port.

mld-snooping overflow-replace [ vlan vlan-list ]

By default, IPv6 multicast group replacement is disabled on a port.

Enabling host tracking

About host tracking

This feature enables the Layer 2 device to record information about member hosts that are receiving IPv6 multicast data. The information includes IPv6 addresses of the hosts, length of time elapsed since the hosts joined IPv6 multicast groups, and remaining timeout time for the hosts. This feature facilitates monitoring and managing member hosts.

Enabling host tracking globally

1.        Enter system view.

system-view

2.        Enter MLD-snooping view.

mld-snooping

3.        Enable host tracking globally.

host-tracking

By default, host tracking is disabled globally.

Enabling host tracking in a VLAN

1.        Enter system view.

system-view

2.        Enter VLAN view.

vlan vlan-id

3.        Enable host tracking for the VLAN.

mld-snooping host-tracking

By default, host tracking is disabled in a VLAN.

Configuring an MLD snooping access control policy

About MLD snooping access control policies

This feature enables the device to use ACLs to filter MLD reports and done messages from IPv6 multicast users. IPv6 multicast users can join or leave only IPv6 multicast groups permitted by the MLD snooping control policies.

Procedure

1.        Enter system view.

system-view

2.        Enter user profile view.

user-profile profile-name

For more information about this command, see user profile commands in Security Command Reference.

3.        Configure an MLD snooping access control policy.

mld-snooping access-policy ipv6-acl-number

By default, no MLD snooping access control policies are configured. IPv6 multicast users can join or leave any IPv6 multicast groups.

Setting the DSCP value for outgoing MLD protocol packets

About the DSCP value for outgoing MLD protocol packets

The DSCP value determines the packet transmission priority. A greater DSCP value represents a higher priority.

Procedure

1.        Enter system view.

system-view

2.        Enter MLD snooping view.

mld-snooping

3.        Set the DSCP value for outgoing MLD protocol packets.

dscp dscp-value

By default, the DSCP value is 48 for outgoing MLD protocol packets.

Display and maintenance commands for MLD snooping

Execute display commands in any view and reset commands in user view.

 

Task

Command

Display Layer 2 IPv6 multicast fast forwarding entries.

display ipv6 l2-multicast fast-forwarding cache [ vlan vlan-id ] [ ipv6-source-address | ipv6-group-address ] * [ slot slot-number ]

Display information about Layer 2 IPv6 multicast groups.

display ipv6 l2-multicast ip [ group ipv6-group-address | source ipv6-source-address ] * [ vlan vlan-id ] [ slot slot-number ]

Display Layer 2 IPv6 multicast group entries.

display ipv6 l2-multicast ip forwarding [ group ipv6-group-address | source ipv6-source-address ] * [ vlan vlan-id ] [ slot slot-number ]

Display information about Layer 2 IPv6 MAC multicast groups.

display ipv6 l2-multicast mac [ mac-address ] [ vlan vlan-id ] [ slot slot-number ]

Display Layer 2 IPv6 MAC multicast group entries.

display ipv6 l2-multicast mac forwarding [ mac-address ] [ vlan vlan-id ] [ slot slot-number ]

Display static IPv6 multicast MAC address entries.

display mac-address [ mac-address [ vlan vlan-id ] | [ multicast ] [ vlan vlan-id ] [ count ] ]

Display MLD snooping status.

display mld-snooping [ global | vlan vlan-id ]

Display dynamic MLD snooping group entries.

display mld-snooping group [ ipv6-group-address | ipv6-source-address ] * [ vlan vlan-id ] [ interface interface-type interface-number | [ verbose ] [ slot slot-number ] ]

Display host tracking information.

display mld-snooping host-tracking vlan vlan-id group ipv6-group-address [ source ipv6-source-address ] [ slot slot-number ]

Display dynamic router port information.

display mld-snooping router-port [ vlan vlan-id ] [ verbose ] [ slot slot-number ]

Display static MLD snooping group entries.

display mld-snooping static-group [ ipv6-group-address | ipv6-source-address ] * [ vlan vlan-id ] [ verbose ] [ slot slot-number ]

Display static router port information.

display mld-snooping static-router-port [ vlan vlan-id ] [ verbose ] [ slot slot-number ]

Display statistics for the MLD messages and IPv6 PIM hello messages learned through MLD snooping.

display mld-snooping statistics

Clear Layer 2 IPv6 multicast fast forwarding entries.

reset ipv6 l2-multicast fast-forwarding cache [ vlan vlan-id ] { { ipv6-source-address | ipv6-group-address } * | all } [ slot slot-number ]

Clear dynamic MLD snooping group entries.

reset mld-snooping group { ipv6-group-address [ ipv6-source-address ] | all } [ vlan vlan-id ]

Clear dynamic router port information.

reset mld-snooping router-port { all | vlan vlan-id }

Clear statistics for MLD messages and IPv6 PIM hello messages learned through MLD snooping.

reset mld-snooping statistics

 

MLD snooping configuration examples

Example: Configuring IPv6 group policy and simulated joining

Network configuration

As shown in Figure 4, Router A runs MLDv1 and acts as the MLD querier, and Switch A runs MLDv1 snooping.

Configure the group policy and simulate joining to meet the following requirements:

·          Host A and Host B receive only the IPv6 multicast data addressed to the IPv6 multicast group FF1E::101. IPv6 multicast data can be forwarded through GigabitEthernet 1/0/3 and GigabitEthernet 1/0/4 of Switch A uninterruptedly, even though Host A and Host B fail to receive the multicast data.

·          Switch A will drop unknown IPv6 multicast data instead of flooding it in VLAN 100.

Figure 4 Network diagram

Procedure

1.        Assign an IPv6 address and prefix length to each interface, as shown in Figure 4. (Details not shown.)

2.        Configure Router A:

# Enable IPv6 multicast routing.

<RouterA> system-view

[RouterA] ipv6 multicast routing

[RouterA-mrib6] quit

# Enable MLD on GigabitEthernet 1/0/1.

[RouterA] interface gigabitethernet 1/0/1

[RouterA-GigabitEthernet1/0/1] mld enable

[RouterA-GigabitEthernet1/0/1] quit

# Enable IPv6 PIM-DM on GigabitEthernet 1/0/2.

[RouterA] interface gigabitethernet 1/0/2

[RouterA-GigabitEthernet1/0/2] ipv6 pim dm

[RouterA-GigabitEthernet1/0/2] quit

3.        Configure Switch A:

# Enable the MLD snooping feature.

<SwitchA> system-view

[SwitchA] mld-snooping

[SwitchA-mld-snooping] quit

# Create VLAN 100, and assign GigabitEthernet 1/0/1 through GigabitEthernet 1/0/4 to the VLAN.

[SwitchA] vlan 100

[SwitchA-vlan100] port gigabitethernet 1/0/1 to gigabitethernet 1/0/4

# Enable MLD snooping, and enable dropping IPv6 unknown multicast data for VLAN 100.

[SwitchA-vlan100] mld-snooping enable

[SwitchA-vlan100] mld-snooping drop-unknown

[SwitchA-vlan100] quit

# Configure an IPv6 multicast group policy so that hosts in VLAN 100 can join only IPv6 multicast group FF1E::101.

[SwitchA] acl ipv6 basic 2001

[SwitchA-acl-ipv6-basic-2001] rule permit source ff1e::101 128

[SwitchA-acl-ipv6-basic-2001] quit

[SwitchA] mld-snooping

[SwitchA–mld-snooping] group-policy 2001 vlan 100

[SwitchA–mld-snooping] quit

# Configure GigabitEthernet 1/0/3 and GigabitEthernet 1/0/4 as simulated member hosts to join IPv6 multicast group FF1E::101.

[SwitchA] interface gigabitethernet 1/0/3

[SwitchA-GigabitEthernet1/0/3] mld-snooping host-join ff1e::101 vlan 100

[SwitchA-GigabitEthernet1/0/3] quit

[SwitchA] interface gigabitethernet 1/0/4

[SwitchA-GigabitEthernet1/0/4] mld-snooping host-join ff1e::101 vlan 100

[SwitchA-GigabitEthernet1/0/4] quit

Verifying the configuration

# Send MLD reports from Host A and Host B to join IPv6 multicast groups FF1E::101 and FF1E::202. (Details not shown.)

# Display dynamic MLD snooping group entries for VLAN 100 on Switch A.

[SwitchA] display mld-snooping group vlan 100

Total 1 entries.

 

VLAN 100: Total 1 entries.

  (::, FF1E::101)

    Host ports (2 in total):

      GE1/0/3                              (00:03:23)

      GE1/0/4                              (00:04:10)

The output shows the following information:

·          Host A and Host B have joined IPv6 multicast group FF1E::101 through the member ports GigabitEthernet 1/0/4 and GigabitEthernet 1/0/3 on Switch A, respectively.

·          Host A and Host B have failed to join the multicast group FF1E::202.

Example: Configuring static ports

Network configuration

As shown in Figure 5:

·          Router A runs MLDv1 and acts as the MLD querier. Switch A, Switch B, and Switch C run MLDv1 snooping.

·          Host A and Host C are permanent receivers of IPv6 multicast group FF1E::101.

Configure static ports to meet the following requirements:

·          To enhance the reliability of IPv6 multicast traffic transmission, configure GigabitEthernet 1/0/3 and GigabitEthernet 1/0/5 on Switch C as static member ports for IPv6 multicast group FF1E::101.

·          Suppose the STP runs on the network. To avoid data loops, the forwarding path from Switch A to Switch C is blocked. IPv6 multicast data flows to the receivers attached to Switch C only along the path of Switch A—Switch B—Switch C. When this path is blocked, a minimum of one MLD query-response cycle must be completed before IPv6 multicast data flows to the receivers along the path of Switch A—Switch C. In this case, the multicast delivery is interrupted during the process. For more information about the STP, see Layer 2—LAN Switching Configuration Guide.

Configure GigabitEthernet 1/0/3 on Switch A as a static router port. Then, IPv6 multicast data can flow to the receivers nearly uninterrupted along the path of Switch A—Switch C when the path of Switch A—Switch B—Switch C is blocked.

Figure 5 Network diagram

Procedure

1.        Assign an IPv6 address and prefix length to each interface, as shown in Figure 5. (Details not shown.)

2.        Configure Router A:

# Enable IPv6 multicast routing.

<RouterA> system-view

[RouterA] ipv6 multicast routing

[RouterA-mrib6] quit

# Enable MLD on GigabitEthernet 1/0/1.

[RouterA] interface gigabitethernet 1/0/1

[RouterA-GigabitEthernet1/0/1] mld enable

[RouterA-GigabitEthernet1/0/1] quit

# Enable IPv6 PIM-DM on GigabitEthernet 1/0/2.

[RouterA] interface gigabitethernet 1/0/2

[RouterA-GigabitEthernet1/0/2] ipv6 pim dm

[RouterA-GigabitEthernet1/0/2] quit

3.        Configure Switch A:

# Enable the MLD snooping feature.

<SwitchA> system-view

[SwitchA] mld-snooping

[SwitchA-mld-snooping] quit

# Create VLAN 100, and assign GigabitEthernet 1/0/1 through GigabitEthernet 1/0/3 to the VLAN.

[SwitchA] vlan 100

[SwitchA-vlan100] port gigabitethernet 1/0/1 to gigabitethernet 1/0/3

# Enable MLD snooping for VLAN 100.

[SwitchA-vlan100] mld-snooping enable

[SwitchA-vlan100] quit

# Configure GigabitEthernet 1/0/3 as a static router port.

[SwitchA] interface gigabitethernet 1/0/3

[SwitchA-GigabitEthernet1/0/3] mld-snooping static-router-port vlan 100

[SwitchA-GigabitEthernet1/0/3] quit

4.        Configure Switch B:

# Enable the MLD snooping feature.

<SwitchB> system-view

[SwitchB] mld-snooping

[SwitchB-mld-snooping] quit

# Create VLAN 100, and assign GigabitEthernet 1/0/1 and GigabitEthernet 1/0/2 to the VLAN.

[SwitchB] vlan 100

[SwitchB-vlan100] port gigabitethernet 1/0/1 gigabitethernet 1/0/2

# Enable MLD snooping for VLAN 100.

[SwitchB-vlan100] mld-snooping enable

[SwitchB-vlan100] quit

5.        Configure Switch C:

# Enable the MLD snooping feature.

<SwitchC> system-view

[SwitchC] mld-snooping

[SwitchC-mld-snooping] quit

# Create VLAN 100, and assign GigabitEthernet 1/0/1 through GigabitEthernet 1/0/5 to the VLAN.

[SwitchC] vlan 100

[SwitchC-vlan100] port gigabitethernet 1/0/1 to gigabitethernet 1/0/5

# Enable MLD snooping for VLAN 100.

[SwitchC-vlan100] mld-snooping enable

[SwitchC-vlan100] quit

# Configure GigabitEthernet 1/0/3 and GigabitEthernet 1/0/5 as static member ports for IPv6 multicast group FF1E::101.

[SwitchC] interface gigabitethernet 1/0/3

[SwitchC-GigabitEthernet1/0/3] mld-snooping static-group ff1e::101 vlan 100

[SwitchC-GigabitEthernet1/0/3] quit

[SwitchC] interface gigabitethernet 1/0/5

[SwitchC-GigabitEthernet1/0/5] mld-snooping static-group ff1e::101 vlan 100

[SwitchC-GigabitEthernet1/0/5] quit

Verifying the configuration

# Display static router port information for VLAN 100 on Switch A.

[SwitchA] display mld-snooping static-router-port vlan 100

VLAN 100:

  Router ports (1 in total):

    GE1/0/3

The output shows that GigabitEthernet 1/0/3 on Switch A has become a static router port.

# Display static MLD snooping group entries in VLAN 100 on Switch C.

[SwitchC] display mld-snooping static-group vlan 100

Total 1 entries).

 

VLAN 100: Total 1 entries).

  (::, FF1E::101)

    Host ports (2 in total):

      GE1/0/3

      GE1/0/5

The output shows that GigabitEthernet 1/0/3 and GigabitEthernet 1/0/5 on Switch C have become static member ports of IPv6 multicast group FF1E::101.

Example: Configuring the MLD snooping querier

Network configuration

As shown in Figure 6:

·          The network is a Layer 2-only network.

·          Source 1 and Source 2 send multicast data to IPv6 multicast groups FF1E::101 and FF1E::102, respectively.

·          Host A and Host C are receivers of IPv6 multicast group FF1E::101, and Host B and Host D are receivers of IPv6 multicast group FF1E::102.

·          All host receivers run MLDv1 and all switches run MLDv1 snooping. Switch A (which is close to the multicast sources) acts as the MLD snooping querier.

To prevent the switches from flooding unknown IPv6 packets in the VLAN, enable all the switches to drop unknown IPv6 multicast packets.

Figure 6 Network diagram

Procedure

1.        Configure Switch A:

# Enable the MLD snooping feature.

<SwitchA> system-view

[SwitchA] mld-snooping

[SwitchA-mld-snooping] quit

# Create VLAN 100, and assign GigabitEthernet 1/0/1 through GigabitEthernet 1/0/3 to the VLAN.

[SwitchA] vlan 100

[SwitchA-vlan100] port gigabitethernet 1/0/1 to gigabitethernet 1/0/3

# Enable MLD snooping, and enable dropping unknown IPv6 multicast data for VLAN 100.

[SwitchA-vlan100] mld-snooping enable

[SwitchA-vlan100] mld-snooping drop-unknown

# Configure Switch A as the MLD snooping querier.

[SwitchA-vlan100] MLD-snooping querier

[SwitchA-vlan100] quit

2.        Configure Switch B:

# Enable the MLD snooping feature.

<SwitchB> system-view

[SwitchB] mld-snooping

[SwitchB-mld-snooping] quit

# Create VLAN 100, and assign GigabitEthernet 1/0/1 through GigabitEthernet 1/0/4 to the VLAN.

[SwitchB] vlan 100

[SwitchB-vlan100] port gigabitethernet 1/0/1 to gigabitethernet 1/0/4

# Enable MLD snooping, and enable dropping unknown IPv6 multicast data for VLAN 100.

[SwitchB-vlan100] mld-snooping enable

[SwitchB-vlan100] mld-snooping drop-unknown

[SwitchB-vlan100] quit

3.        Configure Switch C:

# Enable the MLD snooping feature.

<SwitchC> system-view

[SwitchC] mld-snooping

[SwitchC-mld-snooping] quit

# Create VLAN 100, and assign GigabitEthernet 1/0/1 through GigabitEthernet 1/0/3 to the VLAN.

[SwitchC] vlan 100

[SwitchC-vlan100] port gigabitethernet 1/0/1 to gigabitethernet 1/0/3

# Enable MLD snooping, and enable dropping unknown IPv6 multicast data for VLAN 100.

[SwitchC-vlan100] mld-snooping enable

[SwitchC-vlan100] mld-snooping drop-unknown

[SwitchC-vlan100] quit

4.        Configure Switch D:

# Enable the MLD snooping feature.

<SwitchD> system-view

[SwitchD] mld-snooping

[SwitchD-mld-snooping] quit

# Create VLAN 100, and assign GigabitEthernet 1/0/1 and GigabitEthernet 1/0/2 to the VLAN.

[SwitchD] vlan 100

[SwitchD-vlan100] port gigabitethernet 1/0/1 to gigabitethernet 1/0/2

# Enable MLD snooping, and enable dropping unknown IPv6 multicast data for VLAN 100.

[SwitchD-vlan100] mld-snooping enable

[SwitchD-vlan100] mld-snooping drop-unknown

[SwitchD-vlan100] quit

Verifying the configuration

# Display statistics for MLD messages and IPv6 PIM hello messages learned through MLD snooping on Switch B.

[SwitchB] display mld-snooping statistics

Received MLD general queries:  3

Received MLDv1 specific queries:  0

Received MLDv1 reports:  12

Received MLD dones:  0

Sent     MLDv1 specific queries:  0

Received MLDv2 reports:  0

Received MLDv2 reports with right and wrong records:  0

Received MLDv2 specific queries:  0

Received MLDv2 specific sg queries:  0

Sent     MLDv2 specific queries:  0

Sent     MLDv2 specific sg queries:  0

Received IPv6 PIM hello:  0

Received error MLD messages:  0

The output shows that all switches except Switch A can receive the MLD general queries after Switch A acts as the MLD snooping querier.

Example: Configuring MLD snooping proxying

Network configuration

As shown in Figure 7, Router A runs MLDv1 and acts as the MLD querier. Switch A runs MLDv1 snooping. Configure MLD snooping proxying so that Switch A can perform the following actions:

·          Forward MLD report and done messages to Router A.

·          Respond to MLD queries sent by Router A and forward the queries to downstream hosts.

Figure 7 Network diagram

Procedure

1.        Assign an IPv6 address and subnet mask to each interface, as shown in Figure 7. (Details not shown.)

2.        Configure Router A:

# Enable IPv6 multicast routing.

<RouterA> system-view

[RouterA] ipv6 multicast routing

[RouterA-mrib6] quit

# Enable MLD and IPv6 PIM-DM on GigabitEthernet 1/0/1.

[RouterA] interface gigabitethernet 1/0/1

[RouterA-GigabitEthernet1/0/1] mld enable

[RouterA-GigabitEthernet1/0/1] ipv6 pim dm

[RouterA-GigabitEthernet1/0/1] quit

# Enable IPv6 PIM-DM on GigabitEthernet 1/0/2.

[RouterA] interface gigabitethernet 1/0/2

[RouterA-GigabitEthernet1/0/2] ipv6 pim dm

[RouterA-GigabitEthernet1/0/2] quit

3.        Configure Switch A:

# Enable the MLD snooping feature.

<SwitchA> system-view

[SwitchA] mld-snooping

[SwitchA-mld-snooping] quit

# Create VLAN 100, and assign GigabitEthernet 1/0/1 through GigabitEthernet 1/0/4 to the VLAN.

[SwitchA] vlan 100

[SwitchA-vlan100] port gigabitethernet 1/0/1 to gigabitethernet 1/0/4

# Enable MLD snooping and MLD snooping proxying for the VLAN.

[SwitchA-vlan100] mld-snooping enable

[SwitchA-vlan100] mld-snooping proxy enable

[SwitchA-vlan100] quit

Verifying the configuration

# Send MLD reports from Host A and Host B to join IPv6 multicast group FF1E::101. (Details not shown.)

# Display MLD snooping group entries on Switch A.

[SwitchA] display mld-snooping group

 Total 1 entries.

 

VLAN 100: Total 1 entries.

  (::, FF1E::101)

    Host ports (2 in total):

      GE1/0/3                                     (00:04:09)

      GE1/0/4                                     (00:03:06)

The output shows that GigabitEthernet 1/0/3 and GigabitEthernet 1/0/4 are member ports of IPv6 multicast group FF1E::101. Host A and Host B will receive IPv6 multicast data for the group.

# Display MLD group membership information on Router A.

[RouterA] display mld group

MLD groups in total: 1

 GigabitEthernet1/0/1(2001::1):

  MLD groups reported in total: 1

   Group address: FF1E::101

    Last reporter: FE80::2FF:FFFF:FE00:1

    Uptime: 00:00:31

    Expires: 00:03:48

# Send an MLD done message from Host A to leave IPv6 multicast group FF1E::101. (Details not shown.)

# Display MLD snooping group entries on Switch A.

[SwitchA] display mld-snooping group

Total 1 entries.

 

VLAN 100: Total 1 entries.

  (::, FF1E::101)

    Host ports (1 in total):

      GE1/0/3                                     ( 00:01:23 )

The output shows that GigabitEthernet 1/0/3 is the only member port of IPv6 multicast group FF1E::101. Only Host B will receive IPv6 multicast data for the group.

Troubleshooting MLD snooping

Layer 2 multicast forwarding cannot function

Symptom

Layer 2 multicast forwarding cannot function through MLD snooping.

Solution

To resolve the problem:

1.        Use the display mld-snooping command to display MLD snooping status.

2.        If MLD snooping is not enabled, use the mld-snooping command in system view to enable the MLD snooping feature. Then, use the mld-snooping enable command in VLAN view to enable MLD snooping for the VLAN.

3.        If MLD snooping is enabled globally but not enabled for the VLAN, use the mld-snooping enable command in VLAN view to enable MLD snooping for the VLAN.

4.        If the problem persists, contact H3C Support.

IPv6 multicast group policy does not work

Symptom

Hosts can receive IPv6 multicast data for IPv6 multicast groups that are not permitted by the IPv6 multicast group policy.

Solution

To resolve the problem:

1.        Use the display acl ipv6 command to verify that the configured IPv6 ACL meets the IPv6 multicast group policy requirements.

2.        Use the display this command in MLD-snooping view or in interface view to verify that the correct IPv6 multicast group policy has been applied. If the applied policy is not correct, use the group-policy or mld-snooping group-policy command to apply the correct IPv6 multicast group policy.

3.        Use the display mld-snooping command to verify that dropping unknown IPv6 multicast data is enabled. If it is not, use the mld-snooping drop-unknown command to enable dropping unknown IPv6 multicast data.

4.        If the problem persists, contact H3C Support.