Contents

Configuring multicast VLANs· 1

Overview· 1

Multicast VLAN configuration task list 3

Configuring a sub-VLAN-based multicast VLAN· 3

Configuration prerequisites· 3

Configuration guidelines· 3

Configuration procedure· 3

Configuring a port-based multicast VLAN· 4

Configuration prerequisites· 4

Configuring user port attributes· 4

Assigning user ports to a multicast VLAN· 5

Setting the maximum number of multicast VLAN forwarding entries· 5

Displaying and maintaining multicast VLANs· 6

Multicast VLAN configuration examples· 6

Sub-VLAN-based multicast VLAN configuration example· 6

Port-based multicast VLAN configuration example· 9

 

Configuring multicast VLANs

Overview

As shown in Figure 1, Host A, Host B, and Host C are in different VLANs and the same multicast group. When Switch A (Layer 3 device) receives multicast data for that group, it sends three copies of the multicast data to Switch B (Layer 2 device). This occupies a large amount of bandwidth and increases the burden on the Layer 3 device.

Figure 1 Multicast transmission without the multicast VLAN feature

 

After a multicast VLAN is configured on Switch B, Switch A sends only one copy of the multicast data to the multicast VLAN on Switch B. This method saves network bandwidth and lessens the burden on the Layer 3 device.

Multicast VLANs include sub-VLAN-based multicast VLANs and port-based multicast VLANs.

Sub-VLAN-based multicast VLAN

As shown in Figure 2:

·           Host A, Host B, and Host C are in VLAN 2 through VLAN 4, respectively.

·           On Switch B, VLAN 10 is a multicast VLAN. VLAN 2 through VLAN 4 are sub-VLANs of VLAN 10.

·           IGMP snooping is enabled for the multicast VLAN and its sub-VLANs.

Figure 2 Sub-VLAN-based multicast VLAN

 

IGMP snooping manages router ports in the multicast VLAN and member ports in each sub-VLAN. When Switch A receives multicast data from the multicast source, it sends only one copy of the multicast data to the multicast VLAN on Switch B. Then, Switch B sends a separate copy to each sub-VLAN of the multicast VLAN.

Port-based multicast VLAN

As shown in Figure 3:

·           Host A, Host B, and Host C are in VLAN 2 through VLAN 4, respectively.

·           On Switch B, VLAN 10 is a multicast VLAN.

·           All the user ports (ports with attached hosts) are hybrid ports and assigned to VLAN 10.

·           IGMP snooping is enabled for the multicast VLAN and VLAN 2 through VLAN 4.

Figure 3 Port-based multicast VLAN

 

IGMP snooping manages the router ports and member ports in the multicast VLAN. When Switch A receives multicast data from the multicast source, it sends only one copy of the multicast data to the multicast VLAN on Switch B. Then, Switch B sends a separate copy to each user port in the multicast VLAN.

Forward transmission and reverse transmission

The switch supports both forward transmission and reverse transmission for multicast VLAN.

In forward transmission, multicast receivers are connected to downstream devices of a Layer 2 device. The Layer 2 device forwards multicast traffic only from the upstream Layer 3 device to downstream devices that are in sub-VLANs or have member ports.

In reverse transmission, multicast sources are connected to downstream devices of a Layer 2 device. Upon receiving multicast traffic from a downstream multicast source, the Layer 2 device changes the user VLAN of the traffic to the associated multicast VLAN. Then, it floods the traffic to the upstream Layer 3 device through the multicast VLAN. The upstream Layer 3 device forwards the traffic to receivers based on the associated Layer 3 multicast forwarding entry.

Multicast VLAN configuration task list

Tasks at a glance
(Required.) Perform one of the following tasks: ·          Configuring a sub-VLAN-based multicast VLAN ·          Configuring a port-based multicast VLAN: ¡  Configuring user port attributes ¡  Assigning user ports to a multicast VLAN
(Optional.) Setting the maximum number of multicast VLAN forwarding entries

 

If you have configured both a sub-VLAN-based multicast VLAN and a port-based multicast VLAN on a device, the port-based multicast VLAN configuration takes effect.

Configuring a sub-VLAN-based multicast VLAN

To configure a sub-VLAN-based multicast VLAN, you must configure a VLAN as a multicast VLAN, and assign the VLANs that contain multicast receivers to the multicast VLAN as sub-VLANs.

Configuration prerequisites

Before you configure a sub-VLAN-based multicast VLAN, complete the following tasks:

·           Create VLANs as required.

·           Enable IGMP snooping for the VLAN to be configured as the multicast VLAN, and for the VLANs to be configured as sub-VLANs.

Configuration guidelines

When you configure a sub-VLAN-based multicast VLAN, follow these guidelines:

·           The VLAN to be configured as the multicast VLAN must exist.

·           The VLANs to be configured as sub-VLANs of the multicast VLAN must exist and must not be multicast VLANs or sub-VLANs of any other multicast VLAN.

·           The total number of multicast VLANs on a device must not exceed the upper limit.

Configuration procedure

To configure a sub-VLAN-based multicast VLAN:

 

Step	Command	Remarks
1.      Enter system view.	system-view	N/A
2.      Configure a VLAN as a multicast VLAN and enter its view.	multicast-vlan vlan-id	By default, a VLAN is not a multicast VLAN.
3.      Assign the specified VLANs to the multicast VLAN as sub-VLANs.	subvlan vlan-list	By default, a multicast VLAN does not have any sub-VLANs.

 

Configuring a port-based multicast VLAN

To configure a port-based multicast VLAN, perform the following steps:

1.      Configure a VLAN as the multicast VLAN.

2.      Configure the attributes for user ports that are connected to the multicast receivers.

3.      Assign the user ports to the multicast VLAN.

You can assign a port to a multicast VLAN only when the port is an Ethernet port or a Layer 2 aggregate interface.

Configuration prerequisites

Before you configure a port-based multicast VLAN, complete the following tasks:

·           Create VLANs as required.

·           Enable IGMP snooping for the VLAN to be configured as the multicast VLAN.

·           Enable IGMP snooping for all the VLANs that contain the multicast receivers.

Configuring user port attributes

Step	Command	Remarks
1.      Enter system view.	system-view	N/A
2.      Enter interface view.	interface interface-type interface-number	N/A
3.      Configure the link type of the user port as hybrid.	port link-type hybrid	The default setting is access. For more information about this command, see Layer 2—LAN Switching Command Reference.
4.      Specify the PVID of the current user port as the VLAN to which the user port belongs.	port hybrid pvid vlan vlan-id	By default, the PVID for a hybrid port is VLAN 1. For more information about this command, see Layer 2—LAN Switching Command Reference.
5.      Configure the current user port to permit the multicast VLAN and to untag the packets.	port hybrid vlan vlan-id-list untagged	By default, a hybrid port permits only VLAN 1. For more information about this command, see Layer 2—LAN Switching Command Reference.

 

Assigning user ports to a multicast VLAN

You can either assign the user ports to the multicast VLAN in multicast VLAN view, or assign the user ports to the multicast VLAN in interface view.

When you perform this task, follow these guidelines:

·           The VLAN to be configured as a multicast VLAN must exist.

·           A port can belong to only one multicast VLAN.

Assigning ports to a multicast VLAN in multicast VLAN view

Step	Command	Remarks
1.      Enter system view.	system-view	N/A
2.      Configure a VLAN as a multicast VLAN and enter multicast VLAN view.	multicast-vlan vlan-id	By default, a VLAN is not a multicast VLAN.
3.      Assign ports to the multicast VLAN.	port interface-list	By default, a multicast VLAN does not have any user ports.

 

Assigning a port to a multicast VLAN in interface view

Step	Command	Remarks
1.      Enter system view.	system-view	N/A
2.      Configure a VLAN as a multicast VLAN and enter its view.	multicast-vlan vlan-id	By default, a VLAN is not a multicast VLAN.
3.      Return to system view.	quit	N/A
4.      Enter interface view.	interface interface-type interface-number	N/A
5.      Assign the current port to the multicast VLAN.	port multicast-vlan vlan-id	By default, a user port does not belong to any multicast VLAN.

 

Setting the maximum number of multicast VLAN forwarding entries

You can set the maximum number of multicast VLAN forwarding entries on the device. When the upper limit is reached, the device does not create multicast VLAN forwarding entries until some entries age out or are manually removed.

If the total number of the entries exceeds the upper limit value that you are setting, the system does not automatically remove existing entries or create new entries. As a best practice, remove excess entries manually.

To set the maximum number of multicast VLAN forwarding entries:

 

Step	Command	Remarks
1.      Enter system view.	system-view	N/A
2.      Set the maximum number of multicast VLAN forwarding entries.	multicast-vlan entry-limit limit	The default setting is 128.

 

Displaying and maintaining multicast VLANs

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

 

Task	Command
Display information about multicast VLANs.	display multicast-vlan [ vlan-id ]
Display information about multicast groups in multicast VLANs.	display multicast-vlan group [ source-address | group-address | slot slot-number | verbose | vlan vlan-id ] *
Display multicast VLAN forwarding entries.	display multicast-vlan forwarding-table [ group-address [ mask { mask-length | mask } ] | source-address [ mask { mask-length | mask } ] | slot slot-number | subvlan vlan-id | vlan vlan-id ] *
Clear multicast groups in multicast VLANs.	reset multicast-vlan group [ source-address [ mask { mask-length | mask } ] | group-address [ mask { mask-length | mask } ] | vlan vlan-id ] *

 

Multicast VLAN configuration examples

Sub-VLAN-based multicast VLAN configuration example

Network requirements

As shown in Figure 4:

·           IGMPv2 runs on Layer 3 device Switch A, and IGMPv2 snooping runs on Layer 2 device Switch B.

·           Switch A acts as the IGMP querier.

·           The multicast source sends multicast data to multicast group 224.1.1.1. Host A, Host B, and Host C are receivers. They belong to VLAN 2 through VLAN 4, respectively.

Configure a sub-VLAN-based multicast VLAN on Switch B to meet the following requirements:

·           Switch A sends the multicast data to Switch B through the multicast VLAN.

·           Switch B forwards the multicast data to the receivers in different user VLANs.

Figure 4 Network diagram

 

Configuration procedure

1.      Configure Switch A:

# Enable IP multicast routing.

<SwitchA> system-view

[SwitchA] multicast routing

[SwitchA-mrib] quit

# Create VLAN 20, and assign Ten-GigabitEthernet 1/0/2 to this VLAN.

[SwitchA] vlan 20

[SwitchA-vlan20] port ten-gigabitethernet 1/0/2

[SwitchA-vlan20] quit

# Assign an IP address to VLAN-interface 20, and enable PIM-DM on this interface.

[SwitchA] interface vlan-interface 20

[SwitchA-Vlan-interface20] ip address 1.1.1.2 24

[SwitchA-Vlan-interface20] pim dm

[SwitchA-Vlan-interface20] quit

# Create VLAN 10.

[SwitchA] vlan 10

[SwitchA-vlan10] quit

# Configure Ten-GigabitEthernet 1/0/1 as a hybrid port, and assign it to VLAN 10 as a tagged VLAN member.

[SwitchA] interface ten-gigabitethernet 1/0/1

[SwitchA-Ten-GigabitEthernet1/0/1] port link-type hybrid

[SwitchA-Ten-GigabitEthernet1/0/1] port hybrid vlan 10 tagged

[SwitchA-Ten-GigabitEthernet1/0/1] quit

# Assign an IP address to VLAN-interface 10, and enable IGMP on this interface.

[SwitchA] interface vlan-interface 10

[SwitchA-Vlan-interface10] ip address 10.110.1.1 24

[SwitchA-Vlan-interface10] igmp enable

[SwitchA-Vlan-interface10] quit

2.      Configure Switch B:

# Enable IGMP snooping.

<SwitchB> system-view

[SwitchB] igmp-snooping

[SwitchB-igmp-snooping] quit

# Create VLAN 2, assign Ten-GigabitEthernet 1/0/2 to this VLAN, and enable IGMP snooping in this VLAN.

[SwitchB] vlan 2

[SwitchB-vlan2] port ten-gigabitethernet 1/0/2

[SwitchB-vlan2] igmp-snooping enable

[SwitchB-vlan2] quit

# Create VLAN 3, assign Ten-GigabitEthernet 1/0/3 to this VLAN, and enable IGMP snooping in this VLAN.

[SwitchB] vlan 3

[SwitchB-vlan3] port ten-gigabitethernet 1/0/3

[SwitchB-vlan3] igmp-snooping enable

[SwitchB-vlan3] quit

# Create VLAN 4, assign Ten-GigabitEthernet1/0/4 to this VLAN, and enable IGMP snooping in this VLAN.

[SwitchB] vlan 4

[SwitchB-vlan4] port ten-gigabitethernet 1/0/4

[SwitchB-vlan4] igmp-snooping enable

[SwitchB-vlan4] quit

# Create VLAN 10, and enable IGMP snooping for this VLAN.

[SwitchB] vlan 10

[SwitchB-vlan10] igmp-snooping enable

[SwitchB-vlan10] quit

# Configure Ten-GigabitEthernet 1/0/1 as a hybrid port, and assign it to VLAN 10 as a tagged VLAN member.

[SwitchB] interface ten-gigabitethernet 1/0/1

[SwitchB-Ten-GigabitEthernet1/0/1] port link-type hybrid

[SwitchB-Ten-GigabitEthernet1/0/1] port hybrid vlan 10 tagged

[SwitchB-Ten-GigabitEthernet1/0/1] quit

# Configure VLAN 10 as a multicast VLAN, and configure VLAN 2 through VLAN 4 as sub-VLANs.

[SwitchB] multicast-vlan 10

[SwitchB-mvlan-10] subvlan 2 to 4

[SwitchB-mvlan-10] quit

Verifying the configuration

# Display information about all multicast VLANs on Switch B.

[SwitchB] display multicast-vlan

Total 1 multicast VLANs.

 

Multicast VLAN 10:

  Sub-VLAN list(3 in total):

     2-4

  Port list(0 in total):

# Display multicast VLAN forwarding entries on Switch B.

[SwitchB] display multicast-vlan group

Total 1 entries.

 

Multicast VLAN 10: Total 1 entries.

  (0.0.0.0, 224.1.1.1)

    Sub-VLANs (3 in total):

      VLAN 2

      VLAN 3

      VLAN 4

The output shows that multicast VLAN 10 contains sub-VLANs VLAN 2 through VLAN 4. Switch B will replicate the multicast data of VLAN 10 to VLAN 2 through VLAN 4.

Port-based multicast VLAN configuration example

Network requirements

As shown in Figure 5:

·           IGMPv2 runs on Switch A. IGMPv2 snooping runs on Switch B.

·           Switch A acts as the IGMP querier.

·           The multicast source sends multicast data to multicast group 224.1.1.1. Host A, Host B, and Host C are receivers. They belong to VLAN 2 through VLAN 4, respectively.

Configure a port-based multicast VLAN on Switch B to meet the following requirements:

·           Switch A sends multicast data to Switch B through the multicast VLAN.

·           Switch B forwards the multicast data to the receivers in different user VLANs.

Figure 5 Network diagram

 

Configuration procedure

1.      Configure Switch A:

# Enable IP multicast routing.

<SwitchA> system-view

[SwitchA] multicast routing

[SwitchA-mrib] quit

# Create VLAN 20, and assign Ten-GigabitEthernet 1/0/2 to this VLAN.

[SwitchA] vlan 20

[SwitchA-vlan20] port ten-gigabitethernet 1/0/2

[SwitchA-vlan20] quit

# Assign an IP address to VLAN-interface 20, and enable PIM-DM on this interface.

[SwitchA] interface vlan-interface 20

[SwitchA-Vlan-interface20] ip address 1.1.1.2 24

[SwitchA-Vlan-interface20] pim dm

[SwitchA-Vlan-interface20] quit

# Create VLAN 10, and assign Ten-GigabitEthernet 1/0/1 to the VLAN.

[SwitchA] vlan 10

[SwitchA-vlan10] port ten-gigabitethernet 1/0/1

[SwitchA-vlan10] quit

# Assign an IP address to VLAN-interface 10, and enable IGMP on this interface.

[SwitchA] interface vlan-interface 10

[SwitchA-Vlan-interface10] ip address 10.110.1.1 24

[SwitchA-Vlan-interface10] igmp enable

[SwitchA-Vlan-interface10] quit

2.      Configure Switch B:

# Enable IGMP snooping globally.

<SwitchB> system-view

[SwitchB] igmp-snooping

[SwitchB-igmp-snooping] quit

# Create VLAN 10, assign Ten-GigabitEthernet 1/0/1 to VLAN 10, and enable IGMP snooping for this VLAN.

[SwitchB] vlan 10

[SwitchB-vlan10] port ten-gigabitethernet 1/0/1

[SwitchB-vlan10] igmp-snooping enable

[SwitchB-vlan10] quit

# Create VLAN 2, and enable IGMP snooping for the VLAN.

[SwitchB] vlan 2

[SwitchB-vlan2] igmp-snooping enable

[SwitchB-vlan2] quit

# Create VLAN 3, and enable IGMP snooping for the VLAN.

[SwitchB] vlan 3

[SwitchB-vlan3] igmp-snooping enable

[SwitchB-vlan3] quit

# Create VLAN 4, and enable IGMP snooping for the VLAN.

[SwitchB] vlan 4

[SwitchB-vlan4] igmp-snooping enable

[SwitchB-vlan4] quit

# Configure Ten-GigabitEthernet 1/0/2 as a hybrid port, and configure VLAN 2 as the PVID of the hybrid port.

[SwitchB] interface ten-gigabitethernet 1/0/2

[SwitchB-Ten-GigabitEthernet1/0/2] port link-type hybrid

[SwitchB-Ten-GigabitEthernet1/0/2] port hybrid pvid vlan 2

# Assign Ten-GigabitEthernet 1/0/2 to VLAN 2 and VLAN 10 as an untagged VLAN member.

[SwitchB-Ten-GigabitEthernet1/0/2] port hybrid vlan 2 untagged

[SwitchB-Ten-GigabitEthernet1/0/2] port hybrid vlan 10 untagged

[SwitchB-Ten-GigabitEthernet1/0/2] quit

# Configure Ten-GigabitEthernet 1/0/3 as a hybrid port, and configure VLAN 3 as the PVID of the hybrid port.

[SwitchB] interface ten-gigabitethernet 1/0/3

[SwitchB-Ten-GigabitEthernet1/0/3] port link-type hybrid

[SwitchB-Ten-GigabitEthernet1/0/3] port hybrid pvid vlan 3

# Assign Ten-GigabitEthernet 1/0/3 to VLAN 3 and VLAN 10 as an untagged VLAN member.

[SwitchB-Ten-GigabitEthernet1/0/3] port hybrid vlan 3 untagged

[SwitchB-Ten-GigabitEthernet1/0/3] port hybrid vlan 10 untagged

[SwitchB-Ten-GigabitEthernet1/0/3] quit

# Configure Ten-GigabitEthernet 1/0/4 as a hybrid port, and configure VLAN 4 as the PVID of the hybrid port.

[SwitchB] interface ten-gigabitethernet 1/0/4

[SwitchB-Ten-GigabitEthernet1/0/4] port link-type hybrid

[SwitchB-Ten-GigabitEthernet1/0/4] port hybrid pvid vlan 4

# Assign Ten-GigabitEthernet 1/0/4 to VLAN 4 and VLAN 10 as an untagged VLAN member.

[SwitchB-Ten-GigabitEthernet1/0/4] port hybrid vlan 4 untagged

[SwitchB-Ten-GigabitEthernet1/0/4] port hybrid vlan 10 untagged

[SwitchB-Ten-GigabitEthernet1/0/4] quit

# Configure VLAN 10 as a multicast VLAN.

[SwitchB] multicast-vlan 10

# Assign Ten-GigabitEthernet 1/0/2 and Ten-GigabitEthernet 1/0/3 to VLAN 10.

[SwitchB-mvlan-10] port ten-gigabitethernet 1/0/2 to ten-gigabitethernet 1/0/3

[SwitchB-mvlan-10] quit

# Assign Ten-GigabitEthernet 1/0/4 to VLAN 10.

[SwitchB] interface ten-gigabitethernet 1/0/4

[SwitchB-Ten-GigabitEthernet1/0/4] port multicast-vlan 10

[SwitchB-Ten-GigabitEthernet1/0/4] quit

Verifying the configuration

# Display information about multicast VLANs on Switch B.

[SwitchB] display multicast-vlan

Total 1 multicast VLANs.

 

Multicast VLAN 10:

  Sub-VLAN list(0 in total):

  Port list(0 in total):

    XGE1/0/2

    XGE1/0/3

    XGE1/0/4

# Display IGMP snooping forwarding entries for the dynamic multicast groups on Switch B.

[SwitchB] display igmp-snooping group

Total 1 entries.

 

VLAN 10: Total 1 entries.

  (0.0.0.0, 224.1.1.1)

    Host slots (0 in total):

    Host ports (3 in total):

      XGE1/0/2         (00:03:23)

      XGE1/0/3         (00:04:07)

      XGE1/0/4         (00:04:16)

The output shows that IGMP snooping maintains the user ports in VLAN 10. Switch B will forward the multicast data of VLAN 10 through these user ports.