PIM Snooping Configuration Example

PIM Snooping Configuration Example shows a network configuration that supports PIM snooping.

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PIM Snooping Configuration Example
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In PIM Snooping Configuration Example Layer 3 switches S2, S3, S4, and S5 are connected using the Layer 2 switch S1 through the VLAN comm_vlan. Switches S3, S4, and S5 are multicast capable switches, and switch S2 is a non-multicast capable switch, which has no multicast routing protocol running.

Without PIM snooping, any ingress multicast data traffic on comm_vlan is flooded to all the switches, including switch S2, which does not support multicast traffic. IGMP (Internet Group Management Protocol) snooping does not reduce flooding because it floods the multicast traffic to all router ports.

The network design calls for most multicast traffic to egress switch S5. PIM snooping helps by intercepting the PIM joins received from the downstream routers and forwarding multicast traffic only to those ports that received PIM joins.

Switch S1 (PIM Snooping Switch) Configuration Commands

The following is an example configuration for the PIM snooping switch S1:

create vlan comm_vlan
configure vlan comm_vlan add port 1,2,3,4
disable igmp snooping
disable igmp_snooping comm_vlan
enable pim snooping
enable pim snooping comm_vlan

Switch S3 Configuration Commands

The following is an example configuration for switch S3, which also serves as an RP:

create vlan comm_vlan
configure vlan comm_vlan add port 1
configure comm_vlan ipa 10.172.168.4/24
enable ipforwarding comm_vlan
enable ipmcforwarding comm._vlan
configure pim add vlan comm_vlan sparse
configure ospf add vlan comm._vlan area 0.0.0.0

create vlan sender_vlan
configure vlan sender_vlan add port 2
configure sender_vlan ipa 10.172.169.4/24
enable ipforwarding comm_vlan
enable ipmcforwarding comm._vlan
configure pim add vlan comm._vlan sparse
configure ospf add vlan comm_vlan area 0.0.0.0

enable pim
enable ospf

configure pim crp static 10.172.169.4 pim_policy // RP is configured using the policy pim_policy for the group 224.0.0.0/4

Switch S5 Configuration Commands

The following is an example configuration for switch S5, which serves as the last hop router for multicast traffic:

create vlan comm_vlan
configure vlan comm_vlan add port 1
configure comm_vlan ipa 10.172.168.2/24
enable ipforwarding comm_vlan
enable ipmcforwarding comm._vlan
configure pim add vlan comm_vlan sparse
configure ospf add vlan comm._vlan area 0.0.0.0

create vlan receiver_vlan
configure vlan sender_vlan add port 1
configure sender_vlan ipa 10.172.170.4/24
enable ipforwarding comm_vlan
enable ipmcforwarding comm._vlan
configure pim add vlan comm._vlan sparse
configure ospf add vlan comm_vlan area 0.0.0.0

enable pim
enable ospf

configure pim crp static 10.172.169.4 pim_policy // RP is configured using the policy pim_policy for the group 224.0.0.0/4

Switch S4 Configuration Commands

The following is an example configuration for switch S4, which is neither an LHR nor a RP:

create vlan comm_vlan
configure vlan comm_vlan add port 1
configure comm_vlan ipa 10.172.168.3/24
enable ipforwarding comm_vlan
enable ipmcforwarding comm._vlan
configure pim add vlan comm_vlan sparse
configure ospf add vlan comm._vlan area 0.0.0.0

enable pim
enable ospf

configure pim crp static 10.172.169.4 pim_policy // RP is configured using the policy pim_policy for the group 224.0.0.0/4

Switch S2 Configuration Commands

The following is an example configuration for switch S2, which is not enabled for PIM:

create vlan comm_vlan
configure vlan comm_vlan add port 1
configure comm_vlan ipa 10.172.168.6/24
enable ipforwarding comm_vlan
enable ipmcforwarding comm._vlan
configure ospf add vlan comm._vlan area 0.0.0.0

enable ospf

PIM Snooping Example Configuration Displays

After the example configuration is complete, multicast receivers connect to the network through switch S5 and multicast sources connect through switch S3.

When switch S5 receives an IGMP request from the receiver_vlan for group 225.1.1.1, it sends a PIM (*, G) join towards switch S3, which is the RP. The PIM snooping feature on switch S1 snoops the (*, G) join, and the resulting entry can be viewed by entering the following command at switch S1:

# show pim snooping vlan comm_vlan
PIM Snooping                           ENABLED
Vlan comm_vlan(3971)             Snooping ENABLED
Source         Group           RP               UpPort   DownPort   Age      HoldTime
*              225.1.1.1       10.172.169.4        1        2          15        210
Neighbor IP      DR     Port       Age         Hold Time
10.1272.168.4    YES     1          2            105
10.1272.168.2    NO      2          2            105
10.1272.168.3    NO      3          2            105

Once multicast traffic arrives from the sender_vlan, the LHR (switch S2) sends the (S, G) join message, which is snooped by the PIM snooping switch, switch S1. The resulting entries can be viewed by entering the following command at switch S1:

# show pim snooping vlan comm_vlan
PIM Snooping                           ENABLED
Vlan comm_vlan(3971)             Snooping ENABLED
Source         Group           RP               UpPort   DownPort   Age      HoldTime
*              225.1.1.1       10.172.169.4        1        2          15        210
10.172.169.10  225.1.1.1       10.172.169.4        1        2          15        210
Neighbor IP      DR     Port       Age         Hold Time
10.1272.168.4    YES     1          2            105
10.1272.168.2    NO      2          2            105
10.1272.168.3    NO      3          2            105

Multicast traffic is forwarded only to those ports that have received (*, G) or (S, G) joins and designated router (DR) ports.