06-IP Multicast Configuration Guide

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03-PIM snooping configuration
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Configuring PIM snooping

About PIM snooping

PIM snooping runs on Layer 2 devices. It works with IGMP snooping to analyze received PIM messages, and adds the ports that are interested in specific multicast data to a PIM snooping routing entry. In this way, the multicast data can be forwarded to only the ports that are interested in the data.

Figure 1 Multicast packet transmission without or with PIM snooping

 

As shown in Figure 1, Source 1 sends multicast data to multicast group G1, and Source 2 sends multicast data to multicast group G2. Receiver 1 belongs to G1, and Receiver 2 belongs to G2. The Layer 2 switch's interfaces that connect to the PIM routers are in the same VLAN.

·          When the Layer 2 switch runs only IGMP snooping, it performs the following actions:

a.    Maintains the router ports according to the received PIM hello messages that PIM routers send.

b.    Floods all other types of received PIM messages except PIM hello messages in the VLAN.

c.    Forwards all multicast data to all router ports in the VLAN.

Each PIM router in the VLAN, whether interested in the multicast data or not, can receive all multicast data and all PIM messages except PIM hello messages.

·          When the Layer 2 switch runs both IGMP snooping and PIM snooping, it performs the following actions:

a.    Examines whether a PIM router is interested in the multicast data addressed to a multicast group according to the received PIM messages that the router sends.

b.    Adds only the ports that connect to the router and are interested in the data to a PIM snooping routing entry.

c.    Forwards PIM messages and multicast data to only the routers that are interested in the data, which saves network bandwidth.

For more information about IGMP snooping and the router port, see "Configuring IGMP snooping."

Restrictions and guidelines: PIM snooping configuration

PIM snooping does not take effect on secondary VLANs. As a best practice, do not configure PIM snooping for secondary VLANs. For more information about secondary VLANs, see Layer 2—LAN Switching Configuration Guide.

Make sure the maximum size of a PIM join or prune message is smaller than the path MTU of devices connected to PIM snooping devices. Otherwise, fragmented PIM join or prune messages prevent PIM snooping from correctly forwarding multicast data. For more information about setting the maximum size of a join or prune message, see "Configuring PIM."

PIM snooping is supported only for PIM-SM and PIM-SSM. As a best practice, do not configure PIM snooping for PIM-DM and BIDIR-PIM. For more information about PIM, see "PIM overview."

After you configure PIM snooping for a VLAN, PIM snooping takes effect only on ports that belong to the VLAN.

PIM snooping tasks at a glance

To configure PIM snooping, perform the following tasks:

1.        Enabling PIM snooping

2.        (Optional.) Setting the aging time for global ports after a master/subordinate switchover

¡  Setting the aging time for global neighbor ports

¡  Setting the aging time for global downstream ports and global router ports

Enabling PIM snooping

1.        Enter system view.

system-view

2.        Enable the IGMP snooping feature and enter IGMP-snooping view.

igmp-snooping

By default, IGMP snooping is disabled.

For more information about this command, see IGMP snooping commands in IP Multicast Command Reference.

3.        Return to system view.

quit

4.        Enter VLAN view.

vlan vlan-id

5.        Enable IGMP snooping for the VLAN.

igmp-snooping enable

By default, IGMP snooping is disabled in a VLAN.

For more information about this command, see IP Multicast Command Reference.

6.        Enable PIM snooping for the VLAN.

pim-snooping enable

By default, PIM snooping is disabled in a VLAN.

Setting the aging time for global ports after a master/subordinate switchover

About global ports

A global port is a virtual port on the master device, such as a Layer 2 aggregate interface. A global port that acts as a neighbor port, downstream port, or router port is called a global neighbor port, global downstream port, and global router port, respectively.

Perform this task to decrease Layer 2 multicast data interruption caused by the aging of PIM snooping entries after a master/subordinate switchover.

Restrictions and guidelines

For a global neighbor port, the set aging time does not take effect when the port receives a PIM hello message after a master/subordinate switchover. The aging time for the port is determined by the aging time in the PIM hello message.

For a global router port or global downstream port, the set aging time does not take effect when the port receives a PIM join message after a master/subordinate switchover. The aging time for the port is determined by the aging time in the PIM join message.

Setting the aging time for global neighbor ports

1.        Enter system view.

system-view

2.        Enter VLAN view.

vlan vlan-id

3.        Set the aging time for global neighbor ports after a master/subordinate switchover.

pim-snooping graceful-restart neighbor-aging-time seconds

By default, the aging time for global neighbor ports after a master/subordinate switchover is 105 seconds.

Setting the aging time for global downstream ports and global router ports

1.        Enter system view.

system-view

2.        Enter VLAN view.

vlan vlan-id

3.        Set the aging time for global downstream ports and global router ports after a master/subordinate switchover.

pim-snooping graceful-restart join-aging-time seconds

By default, the aging time for downstream ports and global router ports after a master/subordinate switchover is 210 seconds.

Display and maintenance commands for PIM snooping

Execute display commands in any view and reset commands in user view.

 

Task

Command

Display PIM snooping neighbor information.

display pim-snooping neighbor [ vlan vlan-id ] [ slot slot-number ] [ verbose ]

Display PIM snooping router port information.

display pim-snooping router-port [ vlan vlan-id ] [ slot slot-number ] [ verbose ]

Display PIM snooping routing entries.

display pim-snooping routing-table [ vlan vlan-id ] [ slot slot-number ] [ verbose ]

Display statistics for the PIM messages learned through PIM snooping.

display pim-snooping statistics

Clear statistics for the PIM messages learned through PIM snooping.

reset pim-snooping statistics

 

PIM snooping configuration examples

Example: Configuring PIM snooping

Network configuration

As shown in Figure 2:

·          OSPF runs on the network.

·          Source 1 and Source 2 send multicast data to multicast groups 224.1.1.1 and 225.1.1.1, respectively.

·          Receiver 1 and Receiver 2 belong to multicast groups 224.1.1.1 and 225.1.1.1, respectively.

·          Router C and Router D run IGMP on Twenty-FiveGigE 1/0/1. Router A, Router B, Router C, and Router D run PIM-SM.

·          Twenty-FiveGigE 1/0/2 on Router A acts as a C-BSR and a C-RP.

Configure IGMP snooping and PIM snooping on Switch A. Then, Switch A forwards PIM protocol packets and multicast data packets only to the routers that are connected to receivers.

Figure 2 Network diagram

Procedure

1.        Assign an IP address and subnet mask to each interface, as shown in Figure 2. (Details not shown.)

2.        Configure OSPF on the routers. (Details not shown.)

3.        Configure Router A:

# Enable IP multicast routing.

<RouterA> system-view

[RouterA] multicast routing

[RouterA-mrib] quit

# Enable PIM-SM on each interface.

[RouterA] interface twenty-fivegige 1/0/1

[RouterA-Twenty-FiveGigE1/0/1] pim sm

[RouterA-Twenty-FiveGigE1/0/1] quit

[RouterA] interface twenty-fivegige 1/0/2

[RouterA-Twenty-FiveGigE1/0/2] pim sm

[RouterA-Twenty-FiveGigE1/0/2] quit

# Configure Twenty-FiveGigE 1/0/2 as a C-BSR and a C-RP.

[RouterA] pim

[RouterA-pim] c-bsr 10.1.1.1

[RouterA-pim] c-rp 10.1.1.1

[RouterA-pim] quit

4.        Configure Router B:

# Enable IP multicast routing.

<RouterB> system-view

[RouterB] multicast routing

[RouterB-mrib] quit

# Enable PIM-SM on each interface.

[RouterB] interface twenty-fivegige 1/0/1

[RouterB-Twenty-FiveGigE1/0/1] pim sm

[RouterB-Twenty-FiveGigE1/0/1] quit

[RouterB] interface twenty-fivegige 1/0/2

[RouterB-Twenty-FiveGigE1/0/2] pim sm

[RouterB-Twenty-FiveGigE1/0/2] quit

5.        Configure Router C:

# Enable IP multicast routing.

<RouterC> system-view

[RouterC] multicast routing

[RouterC-mrib] quit

# Enable IGMP on Twenty-FiveGigE 1/0/1.

[RouterC] interface twenty-fivegige 1/0/1

[RouterC-Twenty-FiveGigE1/0/1] igmp enable

[RouterC-Twenty-FiveGigE1/0/1] quit

# Enable PIM-SM on Twenty-FiveGigE 1/0/2.

[RouterC] interface twenty-fivegige 1/0/2

[RouterC-Twenty-FiveGigE1/0/2] pim sm

[RouterC-Twenty-FiveGigE1/0/2] quit

6.        Configure Router D:

# Enable IP multicast routing.

<RouterD> system-view

[RouterD] multicast routing

[RouterD-mrib] quit

# Enable IGMP on Twenty-FiveGigE 1/0/1.

[RouterD] interface twenty-fivegige 1/0/1

[RouterD-Twenty-FiveGigE1/0/1] igmp enable

[RouterD-Twenty-FiveGigE1/0/1] quit

# Enable PIM-SM on Twenty-FiveGigE 1/0/2.

[RouterD] interface twenty-fivegige 1/0/2

[RouterD-Twenty-FiveGigE1/0/2] pim sm

[RouterD-Twenty-FiveGigE1/0/2] quit

7.        Configure Switch A:

# Enable the IGMP snooping feature.

<SwitchA> system-view

[SwitchA] igmp-snooping

[SwitchA-igmp-snooping] quit

# Create VLAN 100, and assign Twenty-FiveGigE 1/0/1 through Twenty-FiveGigE 1/0/4 to the VLAN.

[SwitchA] vlan 100

[SwitchA-vlan100] port twenty-fivegige 1/0/1 to twenty-fivegige 1/0/4

# Enable IGMP snooping and PIM snooping for VLAN 100.

[SwitchA-vlan100] igmp-snooping enable

[SwitchA-vlan100] pim-snooping enable

[SwitchA-vlan100] quit

Verifying the configuration

# On Switch A, display PIM snooping neighbor information for VLAN 100.

[SwitchA] display pim-snooping neighbor vlan 100

Total 4 neighbors.

 

VLAN 100: Total 4 neighbors.

  10.1.1.1

    Ports (1 in total):

      WGE1/0/1                 (00:32:43)

  10.1.1.2

    Ports (1 in total):

      WGE1/0/2                 (00:32:43)

  10.1.1.3

    Ports (1 in total):

      WGE1/0/3                 (00:32:43)

  10.1.1.4

    Ports (1 in total):

      WGE1/0/4                 (00:32:43)

The output shows that Router A, Router B, Router C, and Router D are PIM snooping neighbors.

# On Switch A, display PIM snooping routing entries for VLAN 100.

[SwitchA] display pim-snooping routing-table vlan 100

Total 2 entries.

FSM Flag: NI-no info, J-join, PP-prune pending

 

VLAN 100: Total 2 entries.

  (*, 224.1.1.1)

    Upstream neighbor: 10.1.1.1

      Upstream Ports (1 in total):

        WGE1/0/1

      Downstream Ports (1 in total):

        WGE1/0/3

          Expires: 00:03:01, FSM: J

  (*, 225.1.1.1)

    Upstream neighbor: 10.1.1.2

      Upstream Ports (1 in total):

        WGE1/0/2

      Downstream Ports (1 in total):

        WGE1/0/4

          Expires: 00:03:11, FSM: J

The output shows the following information:

·          Switch A will forward the multicast data intended for multicast group 224.1.1.1 only to Router C.

·          Switch A will forward the multicast data intended for multicast group 225.1.1.1 only to Router D.

Troubleshooting PIM snooping

PIM snooping does not work on a Layer 2 device

Symptom

PIM snooping does not work on a Layer 2 device.

Solution

To resolve the problem:

1.        Use the display current-configuration command to display information about IGMP snooping and PIM snooping.

2.        If IGMP snooping is not enabled, enable the IGMP snooping feature, and then enable IGMP snooping and PIM snooping for the VLAN.

3.        If PIM snooping is not enabled, enable PIM snooping for the VLAN.

4.        If the problem persists, contact H3C Support.