H3C S9500 Series Operating instructions

Brand: H3C

Model: S9500 Series

Category: Network switches

Type: Operating instructions

Operation Manual – MLD Snooping

H3C S9500 Series Routing Switches Table of Contents

Table of Contents

Chapter 1 MLD Snooping Configuration.....................................................................................1-1

1.1 MLD Snooping Overview...................................................................................................1-1

1.1.1 How MLD Snooping Works.....................................................................................1-1

1.1.2 Basic Concepts in MLD Snooping...........................................................................1-2

1.1.3 Work Mechanism of MLD Snooping .......................................................................1-4

1.1.4 Processing of IPv6 Multicast Protocol Messages................................................... 1-6

1.1.5 Protocols and Standards.........................................................................................1-7

1.2 MLD Snooping Configuration Task List.............................................................................1-7

1.3 Configuring Basic Functions of MLD Snooping.................................................................1-8

1.3.1 Configuration Prerequisites.....................................................................................1-8

1.3.2 Enabling MLD Snooping .........................................................................................1-8

1.3.3 Configuring the Version of MLD Snooping..............................................................1-9

1.3.4 Configuring Dynamic Port Aging Timers.................................................................1-9

1.4 Configuring MLD Snooping Port Functions.....................................................................1-10

1.4.1 Configuration Prerequisites...................................................................................1-10

1.4.2 Configuring Static Ports ........................................................................................1-11

1.4.3 Configuring Simulated Joining ..............................................................................1-11

1.4.4 Configuring Fast Leave Processing......................................................................1-12

1.4.5 Configuring MLD Report Suppression ..................................................................1-14

1.5 Configuring MLD-Related Functions................................................................................1-14

1.5.1 Configuration Prerequisites...................................................................................1-14

1.5.2 Enabling MLD Snooping Querier ..........................................................................1-14

1.5.3 Configuring MLD Queries and Responses ...........................................................1-15

1.5.4 Configuring a Source IPv6 Address for MLD Queries ..........................................1-17

1.5.5 Configuring the Function of Dropping Unknown IPv6 Multicast Data...................1-17

1.6 Configuring an IPv6 Multicast Group Policy ....................................................................1-18

1.6.1 Configuration Prerequisites...................................................................................1-18

1.6.2 Configuring an IPv6 Multicast Group Filter...........................................................1-18

1.6.3 Configuring Maximum IPv6 Multicast Groups that Can Be Joined on a Port.......... 1-19

1.6.4 Configuring IPv6 Multicast Group Replacement...................................................1-20

1.7 Displaying and Maintaining MLD Snooping.....................................................................1-21

1.8 MLD Snooping Configuration Examples..........................................................................1-22

1.8.1 Examples 1 (Simulated Joining)............................................................................1-22

1.8.2 Examples 2 (Static Router Port Configuration).....................................................1-25

1.8.3 Examples 3 (MLD Snooping Querier Configuration).............................................1-27

1.9 Troubleshooting MLD Snooping......................................................................................1-28

1.9.1 Switch Fails in Layer 2 Multicast Forwarding........................................................1-28

1.9.2 Configured IPv6 Multicast Group Policy Fails to Take Effect ...............................1-29

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Chapter 1 MLD Snooping Configuration

When configuring MLD Snooping, go to these sections for information you are

interested in:

z MLD Snooping Overview

z MLD Snooping Configuration Task List

z Displaying and Maintaining MLD Snooping

z MLD Snooping Configuration Examples

z Troubleshooting MLD Snooping

 Note:

For details about MLD and IPv6 PIM, refer to MLD Configuration and IPv6 PIM

Configuration in the IP Multicast Volume.

1.1 MLD Snooping Overview

Multicast Listener Discovery Snooping (MLD Snooping) is an IPv6 multicast

constraining mechanism that runs on Layer 2 devices to manage and control IPv6

multicast groups.

1.1.1 How MLD Snooping Works

By analyzing received MLD messages, a Layer 2 device running MLD Snooping

establishes mappings between ports and multicast MAC addresses and forwards IPv6

multicast data based on these mappings.

As shown in

Figure 1-1, when MLD Snooping is not running on the switch (Layer 2

device), IPv6 multicast packets are broadcast to all Layer 2 ports. When MLD Snooping

runs, multicast packets for known IPv6 multicast groups are forwarded to only those

Layer 2 ports with receivers attached to them.

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IPv6 multicast packet transmission

without MLD Snooping

Source

Multicast router

Host A

Receiver

Host B

Host C

Receiver

IPv6 multicast packets

Layer 2 switch

IPv6 multicast packet transmission

when MLD Snooping runs

Source

Multicast router

Host A

Receiver

Host B

Host C

Receiver

Layer 2 switch

Figure 1-1 Before and after MLD Snooping is enabled on a Layer 2 device

1.1.2 Basic Concepts in MLD Snooping

I. MLD Snooping related ports

As shown in Figure 1-2, Router A connects to the multicast source, MLD Snooping runs

on Switch A and Switch B, Host A and Host C are receiver hosts (namely, IPv6 multicast

group members).

Router A Switch A

Switch B

Eth1/1/10 Eth1/1/1

Eth1/1/2

Eth1/1/10

Eth1/1/1

Receiver

Host A

Host B

Host C

Host D

Source

IPv6 multicast packets

Router port

Member port

Figure 1-2 MLD Snooping related ports

Ports involved in MLD Snooping, as shown in

Figure 1-2, are described as follows:

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z Router port: A router port is a port on a Layer 2 switch that leads the switch to a

multicast router (Layer-3 multicast device) or the MLD querier on the subnet. In the

figure, Ethernet 1/1/10 of Switch A and Ethernet 1/1/10 of Switch B are router ports.

A switch registers all its local router ports (including dynamic and static router

ports) in its router port list.

z Member port: A member port (also known as IPv6 multicast group member port or

Listener Port) is a port on a Layer 2 switch that leads the switch to an IPv6

multicast group member. In the figure, Ethernet 1/1/1 and Ethernet 1/1/2 of Switch

A and Ethernet 1/1/1 of Switch B are member ports. The switch records all

member ports (including dynamic and static member ports) on the local device in

the MLD Snooping forwarding table.

 Note:

z Whenever mentioned in this document, a router port is a router-side port on a switch,

rather than a port on a router.

z On an MLD-snooping-enabled switch, the ports that received MLD general queries

with the source address other than 0::0 or IPv6 PIM hello messages are dynamic

router ports. For details about IPv6 PIM hello messages, see IPv6 PIM

Configuration of the IP Multicast Volume.

II. Dynamic port aging timers in MLD Snooping

Table 1-1 Dynamic port aging timers in MLD Snooping and related messages and

actions

Timer Description

Message before

expiry

Action after

expiry

Dynamic router

port aging timer

For each dynamic

router port, the

switch sets a timer

initialized to the

dynamic router

port aging time

MLD general

query of which the

source address is

not 0::0 or IPv6

PIM hello

The switch

removes this port

from its router port

list

Dynamic member

port aging timer

When a port

dynamically joins

an IPv6 multicast

group, the switch

sets a timer for the

port, which is

initialized to the

dynamic member

port aging time.

MLD report

message

The switch

removes this port

from the MLD

Snooping

forwarding table

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 Note:

The port aging mechanism of MLD Snooping works only for dynamic ports; a static port

will never age out.

1.1.3 Work Mechanism of MLD Snooping

Caution:

Only dynamic ports can be automatically added or deleted by the system. Static ports

can be added or deleted only through the corresponding configurations.

A switch running MLD Snooping performs different actions when it receives different

MLD messages, as follows:

I. General queries

The MLD querier periodically sends MLD general queries to all hosts and routers

(FF02::1) on the local subnet to find out whether IPv6 multicast group members exist on

the subnet.

Upon receiving an MLD general query, the switch forwards it through all ports in the

VLAN except the receiving port and performs the following to the port on which it

received the query message:

z If the port is a dynamic router port existing in the router port list, the switch resets

the aging timer for this dynamic router port.

z If the port is not a dynamic router port existing in its router port list, the switch adds

it into the router port list and sets an aging timer for this dynamic router port.

II. Membership reports

A host sends an MLD report to the MLD querier in the following circumstances:

z Upon receiving an MLD query, an IPv6 multicast group member host responds

with an MLD report.

z When intended to join an IPv6 multicast group, a host sends an MLD report to the

MLD querier to announce that it is interested in the multicast information

addressed to that IPv6 multicast group.

Upon receiving an MLD report, the switch forwards it through all the router ports in the

VLAN, resolves the address of the IPv6 multicast group the host is interested in, and

performs the following to the receiving port:

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z If no forwarding table entry exists for the reported group, the switch creates an

entry, adds the port as a dynamic member port into the outgoing port list, and

starts a member port aging timer for that port.

z If a forwarding table entry exists for the reported group, but the port is not included

in the outgoing port list for that group in the forwarding entry, the switch adds the

port as a dynamic member port into the outgoing port list, and starts an aging timer

for that port.

z If a forwarding table entry exists for the reported group and the port is included in

the outgoing port list, which means that this port is already a dynamic member port

for that group, the switch resets the aging timer for that port.

 Note:

A switch will not forward an MLD report through a non-router port in a VLAN.

III. Done messages

When a host leaves an IPv6 multicast group, the host sends an MLD done message to

the multicast router.

When the switch receives an MLD done message on a dynamic member port, the

switch first checks whether a forwarding table entry for the IPv6 multicast group

address in the message exists, and, if one exists, whether the outgoing port list

contains the port.

z If the forwarding table entry does not exist or if the outgoing port list does not

contain the port, the switch discards the MLD done message instead of forwarding

it to any port.

z If the forwarding table entry exists and the outgoing port list contains the port, the

switch forwards the MLD done message to all router ports in the native VLAN.

Because the switch does not know whether any other hosts attached to the port

are still listening to that IPv6 multicast group address, the switch does not

immediately remove the port from the outgoing port list of the forwarding table

entry for that group; instead, it resets the aging timer for the port.

Upon receiving an MLD done message from a host, the MLD querier resolves the IPv6

multicast group address in the message and sends an MLD multicast-address-specific

query to that IPv6 multicast group address through the port that received the MLD done

message. Upon receiving the MLD multicast-address-specific query, the switch

forwards it through all the router ports in the VLAN and all member ports for that IPv6

multicast group, and performs the following to the receiving port:

z If any MLD report in response to the MLD multicast-address-specific query is

received on the port (suppose it is a dynamic member port) before its aging timer

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expires, this means that some host attached to the port is receiving or expecting to

receive IPv6 multicast data for that IPv6 multicast group. The switch resets the

aging timer for the port.

z If no MLD report in response to the MLD multicast-address-specific query is

received on the port before its aging timer expires, this means that no hosts

attached to the port are still listening to that IPv6 multicast group address. The

switch removes the port from the outgoing port list of the forwarding table entry for

that IPv6 multicast group when the aging timer expires.

1.1.4 Processing of IPv6 Multicast Protocol Messages

With Layer 3 IPv6 multicast routing enabled, an MLD Snooping–capable S9500 series

Ethernet switch processes multicast protocol messages differently under different

conditions, specifically as follows:

1) If only MLD is enabled, or both MLD and IPv6 PIM are enabled on the switch, the

switch handles IPv6 multicast protocol messages in the normal way.

2) In only IPv6 PIM is enabled on the switch:

z The switch broadcasts MLD messages as unknown messages in the VLAN.

z Upon receiving an IPv6 PIM hello message, the switch will maintain the

corresponding dynamic router port.

3) When MLD is disabled on the switch:

z If IPv6 PIM is disabled, the switch deletes all its dynamic member ports and

dynamic router ports.

z If IPv6 PIM is enabled, the switch deletes only its dynamic member ports without

deleting its dynamic router ports.

4) When IPv6 PIM is disabled on the switch:

z If MLD is disabled, the switch deletes only its dynamic router ports without deleting

its dynamic member ports.

z If MLD is enabled, the switch maintains all its dynamic member ports and dynamic

router ports.

 Note:

Use the display mld group port-info command to view Layer-2 port information.

For details about the display mld group port-info command, refer to MLD Commands

in the IP Multicast Volume.

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1.1.5 Protocols and Standards

MLD Snooping is documented in RFC 4541: Considerations for Internet Group

Management Protocol (IGMP) and Multicast Listener Discovery (MLD) Snooping

Switches

1.2 MLD Snooping Configuration Task List

Complete these tasks to configure MLD Snooping:

Task Remarks

Enabling MLD Snooping Required

Configuring the Version of MLD

Snooping

Optional

Configuring Basic

Functions of MLD

Snooping

Configuring Dynamic Port Aging

Timers

Optional

Configuring Static Ports Optional

Configuring Simulated Joining Optional

Configuring Fast Leave Processing Optional

Configuring MLD

Snooping Port Functions

Configuring MLD Report Suppression Optional

Enabling MLD Snooping Querier Optional

Configuring MLD Queries and

Responses

Optional

Configuring a Source IPv6 Address

for MLD Queries

Optional

Configuring MLD-Related

Functions

Configuring the Function of Dropping

Unknown IPv6 Multicast Data

Optional

Configuring an IPv6 Multicast Group

Filter

Optional

Configuring Maximum IPv6 Multicast

Groups that Can Be Joined on a Port

Optional

Configuring an IPv6

Multicast Group Policy

Configuring IPv6 Multicast Group

Replacement

Optional

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 Note:

z Configurations made in MLD Snooping view are effective for all VLANs, while

configurations made in VLAN view are effective only for ports belonging to the

current VLAN. For a given VLAN, a configuration made in MLD Snooping view is

effective only if the same configuration is not made in VLAN view.

z Configurations made in MLD Snooping view are effective for all ports; configurations

made in interface view are effective only for the current interface; configurations

made in manual port group view are effective only for all the ports in the current port

group; configurations made in aggregation port group view are effective only for the

master port of the group; configurations made in port group view are effective only

for all the ports in the current port group. For a given port, a configuration made in

MLD Snooping view is effective only if the same configuration is not made in

interface view or port group view.

1.3 Configuring Basic Functions of MLD Snooping

1.3.1 Configuration Prerequisites

Before configuring the basic functions of MLD Snooping, complete the following tasks:

z Configure the corresponding VLANs

Before configuring the basic functions of MLD Snooping, prepare the following data:

z The version of MLD Snooping

z Aging time of router ports

z Aging timer of member ports

1.3.2 Enabling MLD Snooping

Follow these steps to enable MLD Snooping:

To do... Use the command... Remarks

Enter system view

system-view

—

Enable MLD Snooping

globally and enter MLD

Snooping view

mld-snooping

Required

Disabled by default

Return to system view

quit

—

Enter VLAN view

vlan vlan-id

—

Enable MLD Snooping in

the VLAN

mld-snooping enable

Required

Disabled by default

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 Note:

z MLD Snooping must be enabled globally before it can be enabled in a VLAN.

z When you enable MLD Snooping in a specified VLAN, this function takes effect for

ports in this VLAN only.

z After enabling MLD Snooping in a VLAN, you cannot enable MLD and/or IPv6 PIM

on the corresponding VLAN interface, and vice versa.

1.3.3 Configuring the Version of MLD Snooping

By configuring the MLD Snooping version, you actually configure the version of MLD

messages that MLD Snooping can process.

z MLD Snooping version 1 can process MLDv1 messages, but cannot analyze and

process MLDv2 messages, which will be flooded in the VLAN.

z MLD Snooping version 2 can process MLDv1 and MLDv2 messages.

Follow these steps to configure the version of MLD Snooping:

To do… Use the command… Remarks

Enter system view

system-view

—

Enter VLAN view

vlan vlan-id

—

Configure the version of

MLD Snooping

mld-snooping version

version-number

Optional

Version 1 by default

Caution:

If you switch MLD Snooping from version 2 to version 1, the system will clear all MLD

Snooping forwarding entries from dynamic joins, and will:

z Keep forwarding entries from version 2 static (*, G) joins;

z Clear forwarding entries from version 2 static (S, G) joins, which will be restored

when MLD Snooping is switched back to version 2.

For details about static joining, refer to

Configuring Static Ports.

1.3.4 Configuring Dynamic Port Aging Timers

If the switch does not receive an MLD general query or an IPv6 PIM hello message

before the aging timer of a dynamic router port expires, the switch deletes this port from

the router port list when the aging timer times out.

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If the switch does not receive an MLD report for an IPv6 multicast group before the

aging timer of a dynamic member port expires, the switch deletes this port from the

forwarding table for that IPv6 multicast group when the aging timer times out.

If IPv6 multicast group memberships change frequently, you can set a relatively small

value for the member port aging timer, and vice versa.

I. Configuring dynamic port aging timers globally

Follow these steps to configure dynamic port aging timers globally:

To do... Use the command... Remarks

Enter system view

system-view

—

Enter MLD Snooping view

mld-snooping

—

Configure dynamic router

port aging time

router-aging-time

interval

Optional

260 seconds by default

Configure dynamic

member port aging time

host-aging-time interval

Optional

260 seconds by default

II. Configuring dynamic port aging timers in a VLAN

Follow these steps to configure dynamic port aging timers in a VLAN:

To do... Use the command... Remarks

Enter system view

system-view

—

Enter VLAN view

vlan vlan-id

—

Configure dynamic router

port aging time

mld-snooping

router-aging-time

interval

Optional

260 seconds by default

Configure dynamic

member port aging time

mld-snooping

host-aging-time interval

Optional

260 seconds by default

1.4 Configuring MLD Snooping Port Functions

1.4.1 Configuration Prerequisites

Before configuring MLD Snooping port functions, complete the following task:

z Enable MLD Snooping in the VLAN or enable MLD on the desired VLAN interface

z Configure the corresponding port groups

Before configuring MLD Snooping port functions, prepare the following data:

z IPv6 multicast source addresses

z Whether to enable the fast leave function or not

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z Whether to enable the MLD membership report suppression function

1.4.2 Configuring Static Ports

If the host attached to a port is interested in the IPv6 multicast data addressed to a

particular IPv6 multicast group, you can configure this port to be a static member port

for that IPv6 multicast group.

You can configure a port of a switch to be a static router port, through which the switch

can forward all the IPv6 multicast traffic it received..

Follow these steps to configure static ports:

To do... Use the command... Remarks

Enter system view

system-view

—

Enter Ethernet

interface view

interface interface-type

interface-number

Enter the

correspon

ding view

Enter port group

view

port-group { manual

port-group-name | aggregation

agg-id }

Use either

command

Configure a static member

port

mld-snooping static-group

ipv6-group-address [ source-ip

ipv6-source-address ] vlan

vlan-id

Required

No static

member ports

by default

Configure a static router port

mld-snooping

static-router-port vlan vlan-id

Required

No static router

ports by default

 Note:

z A static member port does not respond to queries from the MLD querier; when static

(*, G) or (S, G) joining is enabled or disabled on a port, the port does not send an

unsolicited MLD report or an MLD done message.

z Static member ports and static router ports never age out. To remove such a port,

you need to use the corresponding undo command.

1.4.3 Configuring Simulated Joining

Generally, a host running MLD responds to MLD queries from the MLD querier. If a host

fails to respond due to some reasons, the multicast router will deem that no member of

this IPv6 multicast group exists on the network segment, and therefore will remove the

corresponding forwarding path.

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To avoid this situation from happening, you can enable simulated joining on a port,

namely configure a port of the switch as a simulated member of the IPv6 multicast

group. When an MLD query arrives, that member port will give a response. As a result,

the switch can continue receiving IPv6 multicast data.

Through this configuration, the following functions can be achieved:

z When a port is configured as a simulated member host, it sends an unsolicited

MLD report.

z When receiving an MLD general query, the simulated host responds with an MLD

report just like a real host.

z When the simulated joining function is disabled on a port, the simulated host

sends an MLD done message.

Follow these steps to configure simulated joining:

To do... Use the command... Remarks

Enter system view

system-view

—

Enter Ethernet

interface view

interface interface-type

interface-number

Enter the

correspondin

g view

Enter port group

view

port-group { manual

port-group-name | aggregation

agg-id }

Use either

command

Configure simulated (*, G) or (S,

G) joining

mld-snooping host-join

ipv6-group-address [ source-ip

ipv6-source-address ] vlan

vlan-id

Required

Simulated

joining is

disabled by

default

 Note:

z Each simulated host is equivalent to an independent host. For example, when

receiving an MLD query, the simulated host corresponding to each configuration

responds respectively.

z Unlike a static member port, a port configured as a simulated member host will age

out like a dynamic member port.

1.4.4 Configuring Fast Leave Processing

The fast leave processing feature allows the switch to process MLD done messages in

a fast way. With the fast leave processing feature enabled, when receiving an MLD

done message on a port, the switch immediately removes that port from the outgoing

port list of the forwarding table entry for the indicated group. Then, when receiving MLD

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multicast-address-specific queries for that IPv6 multicast group, the switch will not

forward them to that port.

In VLANs where only one host is attached to each port, fast leave processing helps

improve bandwidth and resource usage.

I. Configuring fast leave processing globally

Follow these steps to configure fast leave processing globally:

To do... Use the command... Remarks

Enter system view

system-view

—

Enter MLD Snooping view

mld-snooping

—

Enable fast leave

processing

fast-leave [ vlan vlan-list ]

Required

Disabled by default

II. Configuring fast leave processing on a port or a group of ports

Follow these steps to configure fast leave processing on a port or a group of ports:

To do... Use the command... Remarks

Enter system view

system-view

—

Enter

Ethernet

interface view

interface interface-type

interface-number

Enter the

correspondi

ng view

Enter port

group view

port-group { manual

port-group-name | aggregation

agg-id }

Use either

command

Enable fast leave processing

mld-snooping fast-leave [ vlan

vlan-list ]

Required

Disabled by

default

Caution:

If fast leave processing is enabled on a port to which more than one host is connected,

when one host leaves an IPv6 multicast group, the other hosts connected to port and

interested in the same IPv6 multicast group will fail to receive IPv6 multicast data

addressed to that group.

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1.4.5 Configuring MLD Report Suppression

When a Layer 2 device receives an MLD report from an IPV6 multicast group member,

the Layer 2 device forwards the message to the Layer 3 device directly connected with

it. Thus, when multiple members belonging to an IPv6 multicast group exist on the

Layer 2 device, the Layer 3 device directly connected with it will receive duplicate MLD

reports from these members.

With the MLD report suppression function enabled, within a query interval, the Layer 2

device forwards only the first MLD report of an IPv6 group to the Layer 3 device and will

not forward the subsequent MLD reports from the same multicast group to the Layer 3

device. This helps reduce the number of packets being transmitted over the network.

Follow these steps to configure MLD report suppression:

To do... Use the command... Remarks

Enter system view

system-view

—

Enter MLD Snooping view

mld-snooping

—

Enable MLD report

suppression

report-aggregation

Optional

Enabled by default

1.5 Configuring MLD-Related Functions

1.5.1 Configuration Prerequisites

Before configuring MLD-related functions, complete the following task:

z Enable MLD Snooping in the VLAN

Before configuring MLD-related functions, prepare the following data:

z MLD general query interval

z MLD last-member query interval

z Maximum response time for MLD general queries

z Source IPv6 address of MLD general queries

z Source IPv6 address of MLD multicast-address-specific queries

z Whether to enable the function of dropping the unknown IPv6 multicast data

1.5.2 Enabling MLD Snooping Querier

In an IPv6 multicast network running MLD, a multicast router or Layer 3 multicast switch

is responsible for sending periodic MLD general queries, so that all Layer 3 multicast

devices can establish and maintain multicast forwarding entries, thus to forward

multicast traffic correctly at the network layer. This router or Layer 3 switch is called

MLD querier.

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However, a Layer 2 multicast switch does not support MLD, and therefore cannot send

MLD general queries by default. By enabling MLD Snooping querier on a Layer 2

switch in a VLAN where multicast traffic needs to be Layer-2 switched only and no

Layer 3 multicast devices are present, the Layer 2 switch will act as the MLD querier to

send periodic MLD general queries, thus allowing multicast forwarding entries to be

established and maintained at the data link layer.

Follow these steps to enable MLD Snooping querier:

To do... Use the command... Remarks

Enter system view

system-view

—

Enter VLAN view

vlan vlan-id

—

Enable the MLD Snooping

querier

mld-snooping querier

Required

Disabled by default

Caution:

z An MLD Snooping querier does not take part in MLD querier election.

z It is meaningless to configure an MLD Snooping querier in an IPv6 multicast

network running MLD; in fact, this may affect MLD querier elections because an

MLD Snooping querier sends MLD general queries with a low source IPv6 address.

z When a device is configured as the MLD Snooping querier of multiple attached

subnets, excessive query tasks will affect device performance. In this case, you can

configure properly longer query intervals than usual.

1.5.3 Configuring MLD Queries and Responses

You can tune the MLD general query interval based on actual condition of the network.

Upon receiving an MLD query (general query or multicast-address-specific query), a

host starts a timer for each IPv6 multicast group it has joined. This timer is initialized to

a random value in the range of 0 to the maximum response time (the host obtains the

value of the maximum response time from the Max Response Time field in the MLD

query it received). When the timer value comes down to 0, the host sends an MLD

report to the corresponding IPv6 multicast group.

An appropriate setting of the maximum response time for MLD queries allows hosts to

respond to queries quickly and avoids bursts of MLD traffic on the network caused by

reports simultaneously sent by a large number of hosts when corresponding timers

expires simultaneously.

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z For MLD general queries, you can configure the maximum response time to fill

their Max Response time field.

z For MLD multicast-address-specific queries, you can configure the MLD

last-member query interval to fill their Max Response time field. Namely, for MLD

multicast-address-specific queries, the maximum response time equals to the

MLD last-member query interval.

I. Configuring MLD queries and responses globally

Follow these steps to configure MLD queries and responses globally:

To do... Use the command... Remarks

Enter system view

system-view

—

Enter MLD Snooping view

mld-snooping

—

Configure the maximum

response time for MLD

general queries

max-response-time

interval

Optional

10 seconds by default

Configure the MLD

last-member query

interval

last-listener-query-inter

val interval

Optional

1 second by default

II. Configuring MLD queries and responses in a VLAN

Follow these steps to configure MLD queries and responses in a VLAN:

To do... Use the command... Remarks

Enter system view

system-view

—

Enter VLAN view

vlan vlan-id

—

Configure MLD general

query interval

mld-snooping

query-interval interval

Optional

60 seconds by default

Configure the maximum

response time for MLD

general queries

mld-snooping

max-response-time

interval

Optional

10 seconds by default

Configure the MLD

last-member query

interval

mld-snooping

last-listener-query-inter

val interval

Optional

1 second by default

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Caution:

In the configuration, make sure that the MLD general query interval is larger than the

maximum response time for MLD general queries. Otherwise, multicast group

members may be deleted by mistake.

1.5.4 Configuring a Source IPv6 Address for MLD Queries

This configuration allows you to change the source IPv6 address of MLD queries.

When a port receives an MLD general query with an all-zero IPv6 address, the switch

does not put it in its router port list. In a multicast network with only Layer 2 devices,

therefore, it is recommended to configure a normal link-local IPv6 address as the

source address of MLD query messages.

Follow these steps to configure source IPv6 addresses of MLD queries:

To do... Use the command... Remarks

Enter system view

system-view

—

Enter VLAN view

vlan vlan-id

—

Configure the source IPv6

address of MLD general

queries

mld-snooping

general-query source-ip

{ current-interface |

ipv6-address }

Optional

FE80::02FF:FFFF:FE00:0

001 by default

Configure the source IPv6

address of MLD

multicast-address-specific

queries

mld-snooping

special-query source-ip

{ current-interface |

ipv6-address }

Optional

FE80::02FF:FFFF:FE00:0

001 by default

Caution:

The source IPv6 address of MLD query messages may affect MLD querier election

within the segment.

1.5.5 Configuring the Function of Dropping Unknown IPv6 Multicast Data

Unknown IPv6 multicast data refers to IPv6 multicast data whose forwarding entries do

not exist in the corresponding MLD Snooping forwarding table:

z With the function of dropping unknown IPv6 multicast data enabled, the switch

drops the unknown IPv6 multicast data received.

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z With the function of dropping unknown IPv6 multicast data disabled, the switch

floods unknown IPv6 multicast data in the native VLAN.

Follow these steps to configure globally the function of dropping unknown IPv6

multicast data:

To do... Use the command... Remarks

Enter system view

system-view

—

Enter MLD Snooping view

mld-snooping

—

Enable the function of

dropping unknown IPv6

multicast data

drop-unknown

Required

Disabled by default

 Note:

When enabled to drop unknown IPv6 multicast data, an S9500 series Ethernet switch

still forwards unknown IPv6 multicast data to other router ports in the VLAN.

1.6 Configuring an IPv6 Multicast Group Policy

1.6.1 Configuration Prerequisites

Before configuring an IPv6 multicast group filtering policy, complete the following tasks:

z Enable MLD Snooping in the VLAN or enable MLD on the desired VLAN interface

z Configure corresponding port groups

Before configuring an IPv6 multicast group filtering policy, prepare the following data:

z IPv6 ACL rule for IPv6 multicast group filtering

z The maximum number of IPv6 multicast groups that can pass the ports

z Whether enable the IPv6 multicast group replacement function.

1.6.2 Configuring an IPv6 Multicast Group Filter

On a MLD Snooping–enabled switch, the configuration of an IPv6 multicast group filter

allows the service provider to define limits of different users’ access.

In an actual application of Video on Demand (VoD), when a user requests a multicast

program, the user’s host initiates an MLD report. Upon receiving this report message,

the switch checks the report against the ACL rule configured on the receiving port. If

this receiving port can join this IPv6 multicast group, the switch adds this port to the

MLD Snooping forwarding table; otherwise the switch drops this report message. Any

IPv6 multicast data that fails the ACL check will not be sent to this port. In this way, the

service provider can control the VoD programs provided for multicast users.

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H3C S9500 Series Operating instructions

Brand: H3C

Model: S9500 Series

Category: Network switches

Type: Operating instructions

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H3C S9500 Series Operating instructions

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