Technical Documentation

Configuring Data MDTs and Provider Tunnels

To configure data multicast distribution trees (MDTs), include the mdt statement:

mdt {data-mdt-reuse;group-range multicast-prefix;threshold {group group-address {source source-address {rate threshold-rate;}}}tunnel-limit limit;}

You can include the statement at the following hierarchy levels:

  • [edit routing-instances routing-instance-name protocols pim]
  • [edit routing-instances routing-instance-name provider-tunnel]
  • [edit logical-systems logical-system-name routing-instances routing-instance-name protocols pim]
  • [edit logical-systems logical-system-name routing-instances routing-instance-name provider-tunnel]

Data MDTs configured at the [edit routing-instances routing-instance-name provider-tunnel] hierarchy level support service provider tunnels operating in source-specific multicast mode. Data MDTs configured at the [edit routing-instances routing-instance-name protocols pim] hierarchy level support service provider tunnels operating in any-source multicast mode.

For an overview of routing instances and a detailed example of routing instance configuration, see the Multicast over Layer 3 VPNs Feature Guide.

By default, automatic creation of data MDTs is disabled.

This section describes the following tasks for configuring data MDTs:

Data MDTs require a correctly configured Layer  3 VPN for multicast. For more information about configuring Layer  3 VPNs for multicast, see Configuring Any-Source Multicast for Draft-Rosen VPNs.

Configuring the Data MDT Group Range

The provider edge (PE) router implementing data MDTs for a local multicast source must be configured with a range of multicast group addresses. Group addresses that fall within the configured range are used in the join messages for the data MDTs created in this VRF instance. The group address range cannot overlap the default MDT group address configured for any VPN on the router. If you configure overlapping group addresses, the configuration commit operation fails.

To configure the data MDT group range, include the group-range statement:

group-range multicast-prefix;

You can include this statement at the following hierarchy levels:

  • [edit routing-instances routing-instance-name protocols pim mdt]
  • [edit routing-instances routing-instance-name provider-tunnel mdt]
  • [edit logical-systems logical-system-name routing-instances routing-instance-name protocols pim mdt]
  • [edit logical-systems logical-system-name routing-instances routing-instance-name provider-tunnel mdt]

Any multicast address range can be used as the multicast prefix, for example, 227.0.0.0/8.

Configuring the Data MDT Threshold Parameters

The PE router implementing data MDTs for a local multicast source must establish a data MDT-creation threshold for a multicast group and source. A multicast group can have more than one source of traffic.

To configure the data MDT-creation threshold, include the threshold statement:

threshold {group group-address {source source-address {rate threshold-rate;}}}

You can include this statement at the following hierarchy levels:

  • [edit routing-instances routing-instance-name protocols pim mdt]
  • [edit routing-instances routing-instance-name provider-tunnel mdt]
  • [edit logical-systems logical-system-name routing-instances routing-instance-name protocols pim mdt]
  • [edit logical-systems logical-system-name routing-instances routing-instance-name provider-tunnel mdt]

The group address is the multicast group address to which the threshold applies. This could be a well-known address for a certain type of multicast traffic.

The source address is the unicast address of the source of the multicast traffic. It can be a source locally attached to or reached through the PE router. A group can have more than one source.

The group and source addresses can be explicit (all 32 bits of the address specified) or a prefix (network address and prefix length specified). Explicit and prefix address forms can be combined if they do not overlap. Overlapping configurations, in which prefix and more explicit address forms are used for the same source or group address, are not supported.

The rate is the threshold applied to the multicast source to automatically create a data MDT. The range is from 10 kilobits per second (Kbps), the default, to 1 gigabit per second (Gbps, equivalent to 1,000,000 Kbps).

Limiting the Maximum Number of Data MDTs

The PE router implementing a data MDT for a local multicast source must establish a limit for the number of data MDTs created in this VRF instance. If the limit is 0 (the default), then no data MDTs are created for this VRF instance.

To configure the data MDT limit, include the tunnel-limit statement:

You can include this statement at the following hierarchy levels:

  • [edit routing-instances routing-instance-name protocols pim mdt]
  • [edit routing-instances routing-instance-name provider-tunnel mdt]
  • [edit logical-systems logical-system-name routing-instances routing-instance-name protocols pim mdt]
  • [edit logical-systems logical-system-name routing-instances routing-instance-name provider-tunnel mdt]

The valid range is from 0 through 1024 for a VRF instance. There is a limit of 8000 tunnels for all data MDTs in all VRF instances on a PE router.

M Series and T Series routers that are connected to a source site require a Tunnel Services PIC to support multicast tunnel (mt) interfaces. MX Series routers do not require Tunnel Services PICs.

A Tunnel Services PIC supports a maximum of 512 multicast tunnel interfaces. Both default and data MDTs contribute to this total. The default MDT uses two multicast tunnel interfaces (one for encapsulation and one for de-encapsulation). To enable an M Series or T Series router to support more than 512 multicast tunnel interfaces, another Tunnel Services PIC is required.

For more information about Tunnel Services PICs and multicast tunnels, see Tunnel Services PICs and Multicast.


Published: 2010-01-12