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play_arrow Overview
- play_arrow Understanding Multicast
play_arrow Managing Group Membership
play_arrow Configuring Protocol Independent Multicast
- play_arrow Understanding PIM
  - PIM Overview
  - PIM on Aggregated Interfaces
- play_arrow Configuring PIM Basics
- play_arrow Routing Content to Densely Clustered Receivers with PIM Dense Mode
- play_arrow Routing Content to Larger, Sparser Groups with PIM Sparse Mode
- play_arrow Configuring Designated Routers
  - Understanding Designated Routers
  - Configuring a Designated Router for PIM
- play_arrow Receiving Content Directly from the Source with SSM
- play_arrow Minimizing Routing State Information with Bidirectional PIM
  - Example: Configuring Bidirectional PIM
- play_arrow Rapidly Detecting Communication Failures with PIM and the BFD Protocol
  - Configuring PIM and the Bidirectional Forwarding Detection (BFD) Protocol
- play_arrow Configuring PIM Options
  - Example: Configuring Nonstop Active Routing for PIM
  - Configuring PIM-to-IGMP and PIM-to-MLD Message Translation
- play_arrow Verifying PIM Configurations
play_arrow Configuring Multicast Routing Protocols
- play_arrow Connecting Routing Domains Using MSDP
  - Examples: Configuring MSDP
  - Configuring Multiple Instances of MSDP
- play_arrow Handling Session Announcements with SAP and SDP
  - Configuring the Session Announcement Protocol
  - Verifying SAP and SDP Addresses and Ports
- play_arrow Facilitating Multicast Delivery Across Unicast-Only Networks with AMT
  - Example: Configuring Automatic IP Multicast Without Explicit Tunnels
- play_arrow Routing Content to Densely Clustered Receivers with DVMRP
  - Examples: Configuring DVMRP
play_arrow Configuring Multicast VPNs
play_arrow General Multicast Options
- play_arrow Bit Index Explicit Replication (BIER)
- play_arrow Prevent Routing Loops with Reverse Path Forwarding
  - Examples: Configuring Reverse Path Forwarding
- play_arrow Use Multicast-Only Fast Reroute (MoFRR) to Minimize Packet Loss During Link Failures
- play_arrow Enable Multicast Between Layer 2 and Layer 3 Devices Using Snooping
- play_arrow Configure Multicast Routing Options
- play_arrow Controller-Based BGP Multicast Signaling
  - Controller-Based BGP Multicast Signaling
play_arrow Troubleshooting
- play_arrow Knowledge Base
  - Knowledge Search
  - JTAC Certified Step-by-Step Troubleshooting: Junos OS Multicast
play_arrow Configuration Statements and Operational Commands
- Junos CLI Reference Overview

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English

Configuring a Designated Router for PIM

date_range 23-Nov-23

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Configuring Interface Priority for PIM Designated Router Selection

A designated router (DR) sends periodic join messages and prune messages toward a group-specific rendezvous point (RP) for each group for which it has active members. When a Protocol Independent Multicast (PIM) router learns about a source, it originates a Multicast Source Discovery Protocol (MSDP) source-address message if it is the DR on the upstream interface.

By default, every PIM interface has an equal probability (priority 1) of being selected as the DR, but you can change the value to increase or decrease the chances of a given DR being elected. A higher value corresponds to a higher priority, that is, greater chance of being elected. Configuring the interface DR priority helps ensure that changing an IP address does not alter your forwarding model.

Note:

DR priority is specific to PIM sparse mode; as per RFC 3973, PIM DR priority cannot be configured explicitly in PIM Dense Mode (PIM-DM) in IGMPv2 – PIM-DM only support DRs with IGMPv1.

To configure the interface designated router priority:

This example shows the configuration for the routing instance. Configure the interface globally or in the routing instance.
```
[edit routing-instances PIM.master protocols pim interface ge-0/0/0.0]
user@host# set priority 5
```

Verify the configuration by checking the Hello Option DR Priority field in the output of the show pim neighbors detail command.

content_copy zoom_out_map
user@host> show pim neighbors detail

content_copy zoom_out_map
Instance: PIM.master
Interface: ge-0/0/0.0
Address: 192.168.195.37, IPv4, PIM v2, Mode: Sparse
Hello Option Holdtime: 65535 seconds
Hello Option DR Priority: 5
Hello Option LAN Prune Delay: delay 500 ms override 2000 ms
Join Suppression supported
Rx Join: Group Source Timeout
225.1.1.1 192.168.195.78 0
225.1.1.1 0

Interface: lo0.0
Address: 10.255.245.91, IPv4, PIM v2, Mode: Sparse
Hello Option Holdtime: 65535 seconds
Hello Option DR Priority: 1
Hello Option LAN Prune Delay: delay 500 ms override 2000 ms
Join Suppression supported

Interface: pd-6/0/0.32768
Address: 0.0.0.0, IPv4, PIM v2, Mode: Sparse
Hello Option Holdtime: 65535 seconds
Hello Option DR Priority: 0
Hello Option LAN Prune Delay: delay 500 ms override 2000 ms
Join Suppression supported

Configuring PIM Designated Router Election on Point-to-Point Links

In PIM sparse mode, enable designated router (DR) election on all PIM interfaces, including point-to-point (P2P) interfaces. (DR election is enabled by default on all other interfaces.) One of the two routers might join a multicast group on its P2P link interface. The DR on that link is responsible for initiating the relevant join messages. (DR priority is specific to PIM sparse mode; as per RFC 3973, PIM DR priority cannot be configured explicitly in PIM Dense Mode (PIM-DM) in IGMPv2 – PIM-DM only support DRs with IGMPv1.)

To enable DR election on point-to-point interfaces:

On both point-to-point link routers, configure the router globally or in the routing instance. This example shows the configuration for the routing instance.
```
[edit routing-instances PIM.master protocols pim]
user@host# set dr-election-on-p2p
```
Verify the configuration by checking the State field in the output of the show pim interfaces command. The possible values for the State field are DR, NotDR, and P2P. When a point-to-point link interface is elected to be the DR, the interface state becomes DR instead of P2P.
If the show pim interfaces command continues to report the P2P state, consider running the restart routing command on both routers on the point-to-point link. Then recheck the state.
CAUTION:
Do not restart a software process unless specifically asked to do so by your Juniper Networks customer support representative. Restarting a software process during normal operation of a routing platform could cause interruption of packet forwarding and loss of data.
```
[edit]
user@host# run restart routing
```

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Multicast Protocols User Guide

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Configuring PIM Designated Router Election on Point-to-Point Links

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Multicast Protocols User Guide

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Configuring a Designated Router for PIM

Configuring Interface Priority for PIM Designated Router Selection

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Configuring PIM Designated Router Election on Point-to-Point Links

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