H3C S9500 Series Operating instructions

H3C
Brand
H3C
Model
S9500 Series
Category
Network switches
Type
Operating instructions
Operation Manual – MLD Snooping
H3C S9500 Series Routing Switches Table of Contents
i
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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Operation Manual – MLD Snooping
H3C S9500 Series Routing Switches Chapter 1 MLD Snooping Configuration
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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
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.
Operation Manual – MLD Snooping
H3C S9500 Series Routing Switches Chapter 1 MLD Snooping Configuration
1-16
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
Operation Manual – MLD Snooping
H3C S9500 Series Routing Switches Chapter 1 MLD Snooping Configuration
1-17
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.
Operation Manual – MLD Snooping
H3C S9500 Series Routing Switches Chapter 1 MLD Snooping Configuration
1-18
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

H3C
Brand
H3C
Model
S9500 Series
Category
Network switches
Type
Operating instructions
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