Working with multicast - Amazon Virtual Private Cloud

Working with multicast

You can configure multicast on transit gateways using the Amazon VPC console or the AWS CLI.

Before you create a multicast domain, you need to know if your hosts use the Internet Group Management Protocol (IGMP) protocol for multicast traffic.

Multicast domain attributes

The following table details the multicast domain attributes. You cannot enable both attributes at the same time.

Attribute Description
Igmpv2Support (AWS CLI)

IGMPv2 support (console)

This attribute determines how group members join or leave a multicast group.

When this attribute is disabled, you must add the group members to the domain manually.

Enable this attribute if at least one member uses the IGMP protocol. Members join the multicast group in one of the following ways:

  • Members that support IGMP use the JOIN and LEAVE messages.

  • Members that do not support IGMP must be added or removed from the group using the Amazon VPC console or the AWS CLI.

If you register multicast group members, you must deregister them, too. The transit gateway ignores an IGMP LEAVE message sent by a manually added group member.

StaticSourcesSupport (AWS CLI)

Static sources support (console)

This attribute determines whether there are static multicast sources for the group.

When this attribute is enabled, you must add sources for a multicast domain using register-transit-gateway-multicast-group-sources . Only multicast sources can send multicast traffic.

When this attribute is disabled, there are no designated multicast sources. Any instances that are in subnets associated with the multicast domain can send multicast traffic, and the group members receive the multicast traffic.

Managing IGMP configurations

When you have at least one host that uses the IGMP protocol for multicast traffic, AWS automatically creates the multicast group when it receives an IGMP JOIN message from an instance, and then adds the instance as a member in this group. You can also statically add non-IGMP hosts as members to a group using the AWS CLI. Any instances that are in subnets associated with the multicast domain can send traffic, and the group members receive the multicast traffic.

Use the following steps to complete the configuration:

  1. Create a VPC. For more information about creating VPCs, see Creating a VPC in the Amazon VPC User Guide.

  2. Create a subnet in the VPC. For more information about creating subnets, see Creating a subnet in your VPC in the Amazon VPC User Guide.

  3. Create a transit gateway configured for multicast traffic. For more information, see Create a transit gateway.

  4. Create a VPC attachment. For more information, see Create a transit gateway attachment to a VPC.

  5. Create a multicast domain configured for IGMP support. For more information, see Creating an IGMP multicast domain.

    Use the following settings:

    • Enable IGMPv2 support.

    • Disable Static sources support.

  6. Create an association between subnets in the transit gateway VPC attachment and the multicast domain. For more information see Associating VPC attachments and subnets with a multicast domain.

  7. The default IGMP version for EC2 is IGMPv3. You need to change the version for all IGMP group members. You can run the following command:

    sudo sysctl net.ipv4.conf.eth0.force_igmp_version=2
  8. Add the members that do not use the IGMP protocol to the multicast group. For more information, see Registering members with a multicast group.

Managing static source configurations

In this configuration, you need to statically add multicast sources in a group. Hosts do not use the IGMP protocol to join or leave multicast groups. You need to statically add the group members that receive the multicast traffic.

Use the following steps to complete the configuration:

  1. Create a VPC. For more information about creating VPCs, see Creating a VPC in the Amazon VPC User Guide.

  2. Create a subnet in the VPC. For more information about creating subnets, see Creating a subnet in your VPC in the Amazon VPC User Guide.

  3. Create a transit gateway configured for multicast traffic. For more information, see Create a transit gateway.

  4. Create a VPC attachment. For more information, see Create a transit gateway attachment to a VPC.

  5. Create a multicast domain configured for no IGMP support, and support for statically adding sources. For more information, see Creating a static source multicast domain.

    Use the following settings:

    • Disable IGMPv2 support.

    • To manually add sources, enable Static sources support.

      The sources are the only resources that can send multicast traffic when the attribute is enabled. Otherwise, any instances that are in subnets associated with the multicast domain can send multicast traffic, and the group members receive the multicast traffic.

  6. Create an association between subnets in the transit gateway VPC attachment and the multicast domain. For more information see Associating VPC attachments and subnets with a multicast domain.

  7. If you enable Static sources support, add the source to the multicast group. For more information, see Registering sources with a multicast group.

  8. Add the members to the multicast group. For more information, see Registering members with a multicast group.

Managing static group member configurations

In this configuration, you need to statically add multicast members to a group. Hosts cannot use the IGMP protocol to join or leave multicast groups. Any instances that are in subnets associated with the multicast domain can send multicast traffic, and the group members receive the multicast traffic.

Use the following steps to complete the configuration:

  1. Create a VPC. For more information about creating VPCs, see Creating a VPC in the Amazon VPC User Guide.

  2. Create a subnet in the VPC. For more information about creating subnets, see Creating a subnet in your VPC in the Amazon VPC User Guide.

  3. Create a transit gateway configured for multicast traffic. For more information, see Create a transit gateway.

  4. Create a VPC attachment. For more information, see Create a transit gateway attachment to a VPC.

  5. Create a multicast domain configured for no IGMP support, and support for statically adding sources. For more information, see Creating a static source multicast domain.

    Use the following settings:

    • Disable IGMPv2 support.

    • Disable Static sources support.

  6. Create an association between subnets in the transit gateway VPC attachment and the multicast domain. For more information see Associating VPC attachments and subnets with a multicast domain.

  7. Add the members to the multicast group. For more information, see Registering members with a multicast group.