Article ID:5763
Introduction
IP multicast is a bandwidth-conserving technology that reduces traffic by simultaneously delivering a single stream of information to potentially thousands of corporate recipients and homes. Applications that take advantage of multicast include video conferencing, corporate communications, distance learning, and distribution of software, stock quotes, and news.
IP multicast delivers application source traffic to multiple receivers without burdening the source or the receivers while using a minimum of network bandwidth. Multicast packets are replicated in the network at the point where paths diverge by Cisco routers enabled with Protocol Independent Multicast (PIM) and other supporting multicast protocols, resulting in the most efficient delivery of data to multiple receivers.
Multicast TV VLANs enable multicast transmissions to subscribers who are not on the same data VLAN without replicating the multicast transmission frames for each subscriber VLAN. Subscribers who are not on the same data VLAN and are connected to the device with different VLAN ID membership can share the same multicast stream by joining the ports to the same Multicast VLAN ID.
Multicast TV VLAN relies on the following Internet Group Management Protocol (IGMP) snooping settings configured on the port:
- Subscribers use IGMP messages to join or leave a Multicast group.
- Device performs IGMP snooping and configures the access port according to its Multicast membership on Multicast TV VLAN.
The device decides for each IGMP packet that is received on an access port whether to associate it with the access VLAN or with the Multicast TV VLAN according to the following rules:
- If an IGMP message is received on an access port, with destination Multicast IP address that is associated with the Multicast TV VLAN of the port, then the software associates the IGMP packet with the Multicast TV VLAN.
- Otherwise, the IGMP message is associated to the access VLAN and the IGMP message is only forwarded within that VLAN.
- The IGMP message is discarded if:
- The Spanning Tree Protocol (STP)/Rapid STP (RSTP) state on the access port is discard.
- The Multiple STP (MSTP) state for the access VLAN is discard.
- The MSTP state for the Multicast TV VLAN is discard, and the IGMP message is associated with this Multicast TV VLAN.
Differences between Regular and Multicast TV VLANs
The table below displays the characteristics of regular vs. Multicast TV VLANs:
|
Feature |
Regular VLAN |
Multicast TV VLAN |
|
VLAN Membership |
Source and all receiver ports must be static members in the same data VLAN. |
Source and receiver ports cannot be members in the same data VLAN. |
|
Group Registration |
All Multicast group registration is dynamic. |
Groups must be associated to Multicast VLAN statically, but actual registration of station is dynamic. |
|
Receiver Ports |
VLAN can be used to both send and receive traffic (both Multicast and Unicast). |
Multicast VLAN can only be used to receive traffic by the stations on the port (only Multicast). |
|
Security and Isolation |
Receivers of same multicast stream are on the same data VLAN and can communicate with each other |
Receivers of same multicast stream are in different Access VLANs and isolated from each other |
The image below displays an example of a network with configured Multicast TV VLAN settings. The SG350X switch has access ports that are configured with Multicast TV VLAN settings, allowing the Receivers to receive multicast packets from the source.
Note: A multicast source can send data to multiple multicast groups at the same time, and multiple multicast sources can send data to the same multicast group at the same time.
Prerequisites in configuring access port Multicast TVVLAN settings on your switch:
- Pre-configured Multicast TV server.
- Create the VLANs. To learn how to configure the VLAN settings on your switch through the web-based utility, click here. For CLI-based instructions, click here.
- Configure IGMP snooping on your switch. For instructions, click here. For CLI-based instructions, click here. (KMGMT-1107)
- Configure TV VLAN settings on your switch. You can configure any of the following:
- Access Port Multicast TV VLAN — For instructions on how to configure Access Port Multicast TV VLAN through the web-based utility of your switch, click here. The CLI-based instructions are provided in this article.
- Customer Port Multicast TV VLAN — For instructions on how to configure Customer Port Multicast TV VLAN through the web-based utility of your switch, click here. For CLI-based instructions, click here.
Objective
The network port which is connected to the multicast server is statically configured as a member in the Multicast VLAN ID. By sending IGMP messages, the network ports communicate with the Multicast server through subscribers and receive the Multicast streams from the Multicast server, while including the Multicast TV VLAN in the multicast packet header. For this reason, the network ports must be statically configured as the following:
- Trunk or general port type
- Member on the Multicast TV VLAN
The subscriber receiver ports can be associated with the Multicast TV VLAN only if it is defined in one of the two following types:
- Access port
- Customer port
This article provides instructions on how to configure access port Multicast TV VLAN settings on a switch through the CLI.
Note: In this scenario, a device is connected to a port in an SG350X switch and that port is going to be configured with multicast TV VLAN settings.
Applicable Devices
- Sx350X Series
- SG350X Series
- SG550X Series
Software Version
- 2.3.0.130
Configure Access Port Multicast TV VLAN
Step 1. Log in to the switch console. The default username and password is cisco/cisco. If you have configured a new username or password, enter the credentials instead.
Note: To learn how to access an SMB switch CLI through SSH or Telnet, click here.
Note: The commands may vary depending on the exact model of your switch. In this example, the SG350X switch is accessed through Telnet.
Step 2. From the Privileged EXEC mode of the switch, enter the Global Configuration mode by entering the following:
Step 3. In the Global Configuration mode, enter the Interface Configuration context by entering the following:
SG350X#interface [interface-id | range interface-The options are:
- interface-id — Specifies an interface ID to be configured.
- range interface-range — Specifies a list of interfaces. Separate nonconsecutive interfaces with a comma and no spaces. Use a hyphen to designate a range of interfaces.
Note: In this example, the interface used is ge1/0/11 where the computer is connected. This computer will become the Receiver of multicast packets.
Step 4. In the Interface Configuration context, use the switchport mode command to configure the VLAN membership mode:
SG350X(config-if)#switchport mode access- access — Specifies an untagged layer 2 VLAN port.
Step 5. (Optional) To return the port to the default VLAN, enter the following:
SG350X(config-if)#no switchport mode accessStep 6. To assign a Multicast TV VLAN to an access port, enter the following:
SG350X(config-if)#switchport access multicast-tv vlan [vlan-id]- vlan-id — Specifies the Multicast TV VLAN ID. A non-existing VLAN can be assigned as a Multicast TV VLAN.
Note: By default, receiving multicast transmissions is disabled. When an existing Multicast TV VLAN is assigned to an access port, the multicast messages received on a membership of the Multicast TV VLAN are forwarded to the access port. All messages received on the access port are bridged only into its Access VLAN. When the port is assigned to a different Multicast TV VLAN, it is automatically removed from its previous VLAN and added it to the new Multicast-TV VLAN.
Note: In this example, the Multicast TV VLAN is VLAN 10.
Step 7. (Optional) To remove the classification rule from the port or range of ports, enter the following:
SG350X(config-if)#no switchport access multicast-tv vlanStep 8. To exit the Interface Configuration context, enter the following:
SG350X(config-if)#exit
Step 9. (Optional) Repeat steps 3 to 8 to configure more access ports into the Multicast TV VLAN.
Note: In this example, the ports ge1/0/12 to 15 are configured on the Multicast TV VLAN 10.
Step 10. (Optional) Enter the end command to go back to the Privileged EXEC mode of the switch:
SG350X(config-if)#end
You should now have successfully configured the access port Multicast TV VLAN settings on your switch through the CLI.
DisplayVLAN Multicast TV Settings
Step 1. To display the receiving ports of Multicast TV VLAN, enter the following:
SG350X#show vlan multicast-tv vlan [vlan-id]
Note: In this example, the configured gi1/0/11 to 15 ports are displayed under the Receiver ports of the Multicast TV VLAN 10 table.
Step 2. (Optional) To display the configuration details a specific port on the VLAN, enter the following:
The options are:
- interface-id — Specifies an Ethernet port.
Note: In this example, interface ge1/0/11 is entered.
Step 3. (Optional) In the Privileged EXEC mode of the switch, save the configured settings to the startup configuration file by entering the following:
SG350X#copy running-config startup-config
Step 4. (Optional) Press Y for Yes or N for No on your keyboard once the Overwrite file [startup-config]… prompt appears.
You should now have displayed the VLAN Multicast TV configuration settings of an access port on your switch.
Important: To proceed with configuring the customer port Multicast TV settings on your switch, follow the prerequisites above.