Configuring PIM-DM

Problem

You want to configure PIM-DM on the routers in your AS.

Solution

Set up PIM-DM on the domains routers:

	[edit protocols]
	aviva@RouterA# set pim interface all mode dense
	aviva@RouterA# set pim interface fe-0/0/0 disable

Discussion

For a small network that has a dense population of receivers and can tolerate the periodic flooding of multicast packets, using PIM-DM is an easier solution than using PIM-SM. With a dense population of receivers, PIM will not need to do much SPT pruning, so you don need PIM-SM. Also, configuring PIM-DM is must simpler than configuring PIM-SM because you don have to set up RPs.

As this recipe shows, to enable PIM-DM, just configure it on all the routers network interfaces. You should explicitly disable it on the routers management interface, either fe-0/0/0 (for J-series, as shown in this recipe) or fxp0 on M-series and T-series routers.

Look at the router interfaces to verify that PIM is running:

	aviva@RouterA> show pim interfaces
	Instance: PIM.master
	Name Stat Mode IP V State Count DR address
	fe-0/0/1.0 Up Dense 4 2 DR 1 10.0.15.2
	lo0.0 Up Dense 4 2 DR 0 192.168.13.1
	se-0/0/2.0 Up Dense 4 2 P2P 1
	se-0/0/3.0 Up Dense 4 2 P2P 1

The output confirms the configuration. All four router interfaces are listed as being up, and the Mode column shows they are all running dense mode. The V column indicates PIM Version 2. The three physical interfaces have each learned about one neighbor. You see that fe-0/0/1 is the DR for 10.0.15.2.

Enabling the JUNOS implementation of PIM automatically turns on IGMPv2, so check the IGMP interfaces:

	aviva@RouterA> show igmp interface
	Interface: fe-0/0/1.0
	 Querier: 10.0.15.1
	 State: Up Timeout: 187 Version: 2 Groups: 0
	Interface: se-0/0/3.0
	 Querier: 10.0.16.1
	 State: Up Timeout: None Version: 2 Groups: 4
	Interface: se-0/0/2.0
	 Querier: 10.0.21.1
	 State: Up Timeout: None Version: 2 Groups: 4

	Configured Parameters:
	IGMP Query Interval: 125.0
	IGMP Query Response Interval: 10.0

	IGMP Last Member Query Interval: 1.0
	IGMP Robustness Count: 2

	Derived Parameters:
	IGMP Membership Timeout: 260.0
	IGMP Other Querier Present Timeout: 255.0

This output confirms that IGMPv2 is running on the three PIM interfaces.

In this network, a host on 10.0.15.2 is a source for group 225.1.1.1, and the receiver is on RouterB. To check PIM-DM forwarding, first check for multicast routes:

	aviva@RouterA> show multicast route
	Address family INET
	Group: 225.1.1.1
	 Source: 10.0.15.1/32
	 Upstream interface: fe-0/0/1.0
	 Downstream interface list:
	 se-0/0/2.0
	Address family INET6

RouterA has a multicast route for the group 225.1.1.1, and the source is 10.0.15.1, which is RouterEs subnet. The downstream interface toward the receiver is se-0/0/2, which you can confirm with the show multicast next-hops command:

	aviva@RouterA> show multicast next-hops inet
	Family: INET
	ID Refcount KRefcount Downstream interface
	348 2 1 se-0/0/2.0

Also, check the PIM join state on the router:

	aviva@RouterA> show pim join extensive inet
	Instance: PIM.master Family: INET
	Group: 225.1.1.1
	 Source: 10.0.15.1
	 Flags: dense
	 Upstream interface: fe-0/0/1.0
	 Upstream neighbor: 10.0.15.1
	 Downstream interfaces:
	 se-0/0/3.0 (Pruned timeout 254)
	 se-0/0/2.0

This output illustrates the PIM-DM flood-and-prune operation. Because there is only one receiver, on RouterB, PIM-DM maintains an SPT that includes se-0/0/2 (the interface to RouterB) but prunes the SPT from RouterG (interface se-0/0/3).