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PIM Snooping for VPLS

 

Understanding PIM Snooping for VPLS

There are two ways to direct PIM control packets:

  • By the use of PIM snooping

  • By the use of PIM proxying

PIM snooping configures a device to examine and operate only on PIM hello and join/prune packets. A PIM snooping device snoops PIM hello and join/prune packets on each interface to find interested multicast receivers and populates the multicast forwarding tree with this information. PIM snooping differs from PIM proxying in that both PIM hello and join/prune packets are transparently flooded in the VPLS as opposed to the flooding of only hello packets in the case of PIM proxying. PIM snooping is configured on PE routers connected through pseudowires. PIM snooping ensures that no new PIM packets are generated in the VPLS, with the exception of PIM messages sent through LDP on pseudowires.

Note

In the VPLS documentation, the word router in terms such as PE router is used to refer to any device that provides routing functions.

A device that supports PIM snooping snoops hello packets received on attachment circuits. It does not introduce latency in the VPLS core when it forwards PIM join/prune packets.

To configure PIM snooping on a PE router, use the pim-snooping statement at the [edit routing-instances instance-name protocols] hierarchy level:

Example: Configuring PIM Snooping for VPLS explains the PIM snooping method. The use of the PIM proxying method is not discussed here and is outside the scope of this document. For more information about PIM proxying, see PIM Snooping over VPLS.

Example: Configuring PIM Snooping for VPLS

This example shows how to configure PIM snooping in a virtual private LAN service (VPLS) to restrict multicast traffic to interested devices.

Requirements

This example uses the following hardware and software components:

  • M Series Multiservice Edge Routers (M7i and M10i with Enhanced CFEB, M120, and M320 with E3 FPCs) or MX Series 5G Universal Routing Platforms (MX80, MX240, MX480, and MX960)

  • Junos OS Release 13.2 or later

Overview

The following example shows how to configure PIM snooping to restrict multicast traffic to interested devices in a VPLS.

Note

This example demonstrates PIM snooping by the use of a PIM snooping device to restrict multicast traffic. The use of the PIM proxying method to achieve PIM snooping is out of the scope of this document and is yet to be implemented in Junos OS.

Topology

In this example, two PE routers are connected to each other through a pseudowire connection. Router PE1 is connected to Routers CE1 and CE2. A multicast receiver is attached to Router CE2. Router PE2 is connected to Routers CE3 and CE4. A multicast source is connected to Router CE3, and a second multicast receiver is attached to Router CE4.

PIM snooping is configured on Routers PE1 and PE2. Hence, data sent from the multicast source is received only by members of the multicast group.

Figure 1 shows the topology used in this example.

Figure 1: PIM Snooping for VPLS
PIM Snooping for VPLS

Configuration

CLI Quick Configuration

To quickly configure this example, copy the following commands, paste them into a text file, remove any line breaks, change any details necessary to match your network configuration, and then copy and paste the commands into the CLI at the [edit] hierarchy level.

Router PE1

Router CE1

Router CE2

Router PE2

Router CE3 (RP)

Router CE4

Configuring PIM Snooping for VPLS

Step-by-Step Procedure

The following example requires that you navigate various levels in the configuration hierarchy. For information about navigating the CLI, see Using the CLI Editor in Configuration Mode in the CLI User Guide.

Note

This section includes a step-by-step configuration procedure for one or more routers in the topology. For comprehensive configurations for all routers, see CLI Quick Configuration.

To configure PIM snooping for VPLS:

  1. Configure the router interfaces forming the links between the routers.
    Note

    ge-2/0/0.0 and ge-2/0/1.0 are configured as VPLS interfaces and connect to Routers CE3 and CE4. See Virtual Private LAN Service User Guide for more details.

    Note

    The ge-2/0/1.0 interface on Router CE3 connects to the multicast source.

    Note

    The ge-2/0/1.0 interface on Router CE4 connects to a multicast receiver.

    Similarly, configure Routers PE1, CE1, and CE2.

  2. Configure the router IDs of all routers.

    Similarly, configure other routers.

  3. Configure an IGP on interfaces of all routers.

    Similarly, configure other routers.

  4. Configure the LDP, MPLS, and BGP protocols on the PE routers.

    The BGP group is required for interfacing with the other PE router. Similarly, configure Router PE1.

  5. Configure PIM on all CE routers.

    Ensure that Router CE3 is configured as the rendezvous point (RP) and that the RP address is configured on other CE routers.

    Similarly, configure Routers CE1 and CE2.

  6. Configure multicast snooping options on the PE routers.

    Similarly, configure Router PE1.

  7. Create a routing instance (titanium), and configure the VPLS on the PE routers.

    Similarly, configure Router PE1.

  8. Configure PIM snooping on the PE routers.

    Similarly, configure Router PE1.

Results

From configuration mode, confirm your configuration by entering the show interfaces, show routing-options, show protocols, show multicast-snooping-options, and show routing-instances commands.

If the output does not display the intended configuration, repeat the instructions in this example to correct the configuration.

user@PE2# show interfaces
user@PE2# show routing-options
user@PE2# show protocols
user@PE2# show multicast-snooping-options
user@PE2# show routing-instances

Similarly, confirm the configuration on all other routers. If you are done configuring the routers, enter commit from configuration mode.

Note

Use the show protocols command on the CE routers to verify the configuration for the PIM RP .

Verification

Confirm that the configuration is working properly.

Verifying PIM Snooping for VPLS

Purpose

Verify that PIM Snooping is operational in the network.

Action

To verify that PIM snooping is working as desired, use the following commands:

  1. From operational mode on Router PE2, run the show pim snooping interfaces command.
    user@PE2> show pim snooping interfaces

    The output verifies that PIM snooping is configured on the two interfaces connecting Router PE2 to Routers CE3 and CE4.

    Similarly, check the PIM snooping interfaces on Router PE1.

  2. From operational mode on Router PE2, run the show pim snooping neighbors detail command.
    user@PE2> show pim snooping neighbors detail

    The output verifies that Router PE2 can detect the IP addresses of its PIM snooping neighbors (10.0.0.18 on CE3 and 10.0.0.22 on CE4).

    Similarly, check the PIM snooping neighbors on Router PE1.

  3. From operational mode on Router PE2, run the show pim snooping statistics command.
    user@PE2> show pim snooping statistics

    The output shows the number of hello and join/prune messages received by Router PE2. This verifies that PIM sparse mode is operational in the network.

  4. Send multicast traffic from the source terminal attached to Router CE3, for the multicast group 203.0.113.1.
  5. From operational mode on Router PE2, run the show pim snooping join, show pim snooping join extensive, and show multicast snooping route extensive instance <instance-name> group <group-name> commands to verify PIM snooping.
    user@PE2> show pim snooping join
    user@PE2> show pim snooping join extensive

    The outputs show that multicast traffic sent for the group 203.0.113.1 is sent to Receiver 2 through Router CE4 and also display the upstream and downstream neighbor details.

    user@PE2> show multicast snooping route extensive instance titanium group 203.0.113.1

Meaning

PIM snooping is operational in the network.