Example: Configuring DVMRP

This example shows how to use DVMRP to announce routes used for multicast routing as well as multicast data forwarding.

• 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 is a distance vector protocol for multicast. It is similar to RIP, in that both RIP and DVMRP have issues with scalability and robustness challenges. PIM domains are more commonly used than DVMRP domains. In some environments, you might need to configure interoperability with DVMRP.

This example includes the following DVMRP settings:

• protocols dvmrp rib-group—Associates the dvmrp-rib routing table group with the DVMRP protocol to enable multicast RPF lookup.
• protocols dvmrp interface—Configures the DVMRP interface. The interface of a DVMRP router can be either a physical interface to a directly attached subnetwork or a tunnel interface to another multicast-capable area of the Multicast Backbone (MBone). The DVMRP hold-time period is the amount of time that a neighbor is to consider the sending router (this router) to be operative (up). The default hold-time period is 35 seconds.
• protocols dvmrp interface hold-time—The DVMRP hold-time period is the amount of time that a neighbor is to consider the sending router (this router) to be operative (up). The default hold-time period is 35 seconds.
• protocols dvmrp interface metric—All interfaces can be configured with a metric specifying cost for receiving packets on a given interface. The default metric is 1.

  For each source network reported, a route metric is associated with the unicast route being reported. The metric is the sum of the interface metrics between the router originating the report and the source network. A metric of 32 marks the source network as unreachable, thus limiting the breadth of the DVMRP network and placing an upper bound on the DVMRP convergence time.

• routing-options rib-groups—Enables DVMRP to access route information from the unicast routing table, inet.0, and from a separate routing table that is reserved for DVMRP. In this example, the first routing table group named ifrg contains local interface routes. This ensures that local interface routes get added to both the inet.0 table for use by unicast protocols and the inet.2 table for multicast RPF check. The second routing table group named dvmrp-rib contains inet.2 routes.

  DVMRP needs to access route information from the unicast routing table, inet.0, and from a separate routing table that is reserved for DVMRP. You need to create the routing table for DVMRP and to create groups of routing tables so that the routing protocol process imports and exports routes properly. We recommend that you use routing table inet.2 for DVMRP routing information.

• routing-options interface-routes— After defining the ifrg routing table group, use the interface-routes statement to insert interface routes into the ifrg group—in other words, into both inet.0 and inet.2. By default, interface routes are imported into routing table inet.0 only.
• sap—Enables Session Directory Announcement Protocol (SAP) and Session Directory Protocol (SDP). Enabling SAP allows the router to receive announcements about multimedia and other multicast sessions.

  SAP always listens to the address and port 224.2.127.254:9875 for session advertisements. To add other addresses or pairs of address and port, include one or more listen statements.

  Sessions learned by SDP, SAP's higher-layer protocol, time out after 60 minutes.

Configuration

CLI Quick Configuration

To quickly configure DVMRP, 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. Create the routing tables for DVMRP routes.

   [edit]user@host# edit routing-options[edit routing-options]user@host# set interface-routes rib-group ifrg[edit routing-options]user@host# set rib-groups ifrg import-rib [ inet.0 inet.2 ][edit routing-options]user@host# set rib-groups dvmrp-rib import-rib inet.2[edit routing-options]user@host# set rib-groups dvmrp-rib export-rib inet.2[edit routing-options]user@host# exit
2. Configure SAP and SDP.
   [edit]user@host# edit protocols[edit protocols]user@host# set sap
3. Enable DVMRP on the router and associate the dvmrp-rib routing table group with DVMRP to enable multicast RPF checks.
   [edit protocols]user@host# set dvmrp rib-group dvmrp-rib
4. Configure the DVMRP interface with a hold-time value and a metric. This example shows an IP-over-IP encapsulation tunnel interface.
   [edit protocols]user@host# set dvmrp interface ip–0/0/0.0[edit protocols]user@host# set dvmrp interface ip–0/0/0.0 hold-time 40[edit protocols]user@host# set dvmrp interface ip–0/0/0.0 metric 5

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

   [edit protocols]user@host# commit

Results

Confirm your configuration by entering the show routing-options command and the show protocols 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 dvmrp neighbors

Related Topics

• DVMRP Overview
• Example: Configuring DVMRP to Announce Unicast Routes