Example: Configuring DVMRP to Announce Unicast Routes

This example shows how to use DVMRP to announce unicast routes used solely for multicast reverse-path forwarding (RPF) to set up the multicast control plane.

• Requirements
• Overview
• Configuration
• Verification

Requirements

Before you begin:

• Configure the router interfaces. See the Network Interfaces Configuration Guide.
• Configure an interior gateway protocol or static routing. See the Routing Protocols Configuration Guide.

Overview

DVMRP has two modes. Forwarding mode is the default mode. In forwarding mode, DVMRP is responsible for the multicast control plane and multicast data forwarding. In the nondefault mode (which is shown in this example), DVMRP does not forward multicast data traffic. This mode is called unicast routing mode because in this mode DVMRP is only responsible for announcing unicast routes used for multicast RPF—in other words, for establishing the control plane. To forward multicast data, enable Protocol Independent Multicast (PIM) on the interface. If you have configured PIM on the interface, as shown in this example, you can configure DVMRP in unicast-routing mode only. You cannot configure PIM and DVMRP in forwarding mode at the same time.

This example includes the following settings:

• policy-statement dvmrp-export—Accepts static default routes.
• protocols dvmrp export dvmrp-export—Associates the dvmrp-export policy with the DVMRP protocol.

  All routing protocols use the routing table to store the routes that they learn and to determine which routes they advertise in their protocol packets. Routing policy allows you to control which routes the routing protocols store in and retrieve from the routing table. Import and export policies are always from the point of view of the routing table. So the dvmrp-export policy exports static default routes from the routing table and accepts them into DVMRP.

• protocols dvmrp interface all mode unicast-routing—Enables all interfaces to announce unicast routes used solely for multicast RPF.
• protocols dvmrp rib-group inet dvmrp-rg—Associates the dvmrp-rib routing table group with the DVMRP protocol to enable multicast RPF checks.
• protocols pim rib-group inet pim-rg—Associates the pim-rg routing table group with the PIM protocol to enable multicast RPF checks.
• routing-options rib inet.2 static route 0.0.0.0/0 discard—Redistributes static routes to all DVMRP neighbors. The inet.2 routing table stores unicast IPv4 routes for multicast RPF lookup. The discard statement silently drops packets without notice.
• routing-options rib-groups dvmrp-rg import-rib inet.2—Creates the routing table for DVMRP to ensure that the routing protocol process imports routes properly.
• routing-options rib-groups dvmrp-rg export-rib inet.2—Creates the routing table for DVMRP to ensure that the routing protocol process exports routes properly.
• routing-options rib-groups pim-rg import-rib inet.2—Enables access to route information from the routing table that stores unicast IPv4 routes for multicast RPF lookup. In this example, the first routing table group named pim-rg contains local interface routes. This ensures that local interface routes get added to the inet.2 table.

Configuration

CLI Quick Configuration

To quickly configure DVMRP in unicast routing mode, copy the following commands into a text file and then paste the commands into the CLI.

Step-by-Step Procedure

The following example requires you to navigate various levels in the configuration hierarchy. For information about navigating the CLI, see Modification of the Junos OS Configuration in Junos OS CLI, Release 10.3.

To configure an MSDP routing instance:

1. Configure the routing options.

   [edit]user@host# edit routing-options[edit routing -options]user@host# set rib inet.2 static route 0.0.0.0/0 discard[edit policy-options]user@host# set rib-groups pim-rg import-rib inet.2[edit policy-options]user@host# set rib-groups dvmrp-rg import-rib inet.2[edit policy-options]user@host# set rib-groups dvmrp-rg export-rib inet.2[edit policy-options]user@host# exit
2. Configure DVMRP.
   [edit]user@host# edit protocols[edit protocols]user@host# set dvmrp rib-group inet dvmrp-rg[edit protocols]user@host# set dvmrp export dvmrp-export[edit protocols]user@host# set dvmrp interface all mode unicast-routing[edit protocols]user@host# set dvmrp interface fxp0 disable
3. Configure PIM so that PIM performs multicast data forwarding.
   [edit protocols]user@host# set pim rib-group inet pim-rg[edit protocols]user@host# set pim interface all[edit protocols]user@host# exit
4. Configure the DVMRP routing policy.
   [edit policy-options policy-statement dvmrp-export term 10]user@host# set from protocol static[edit policy-options policy-statement dvmrp-export term 10]user@host# set from route-filter 0.0.0.0/0 exact[edit policy-options policy-statement dvmrp-export term 10]user@host# set then accept

5. If you are done configuring the device, commit the configuration.

   [edit protocols]user@host# commit

Results

Confirm your configuration by entering the show policy-options command, the show protocolscommand, and the show routing-options command from configuration mode. If the output does not display the intended configuration, repeat the configuration instructions in this example to correct it.

Verification

To verify the configuration, run the following commands:

• show dvmrp interfaces
• show pim statistics

Related Topics

• DVMRP Overview
• Example: Configuring DVMRP