Multicast-Stub Multicast Routing & IGMP Helper

Stub multicast routing is useful in situations where you have small remote sites connected to a centralized WAN cloud across low-bandwidth links that use low-end routers. This forwards all IGMP messages to the central router, without processing the typical IGMP report and query messages necessary itself, to make PIM work. If both routers were to run PIM SM, R8 would have to accept RP discovery messages, build its own RP cache, and maintain states for all multicast groups joined by local receivers, thus possibly over-taxing a small router’s resources. Being a stub multicast router allows R8 to be exempted from PIM and IGMP message processing.
 
R1(config)#
interface FastEthernet0/0
 ip address 12.1.1.1 255.255.255.0
 ip pim sparse-mode
 duplex auto
 speed auto
end
R2(config)#
interface FastEthernet0/0
 ip address 12.1.1.2 255.255.255.0
 ip pim sparse-mode
 duplex auto
 speed auto
end
!
interface FastEthernet0/1
 ip address 23.1.1.2 255.255.255.0
 ip pim sparse-mode
 duplex auto
 speed auto
end
R3(config)#
interface FastEthernet0/0
 ip address 23.1.1.3 255.255.255.0
 ip pim sparse-mode
 duplex auto
 speed auto
end
interface FastEthernet0/0
 ip address 34.1.1.4 255.255.255.0
 ip pim dense-mode
 duplex auto
 speed auto
end
R5(config-if)#
interface FastEthernet0/0
 ip address 45.1.1.5 255.255.255.0
 ip pim dense-mode
 ip igmp join-group 224.1.1.1
 duplex auto
 speed auto
end

Pinging from R1
 
Applying Filter on R3
R3(config)#access-list 10 deny host 34.1.1.4
R3(config)#access-list 10 permit any
R3(config)#int f0/1
R3(config-if)#ip pim neighbor-filter 10
 
Reply on R1 Fails

Configuring igmp Helper on R4
R4#
interface FastEthernet0/1
 ip address 45.1.1.4 255.255.255.0
 ip pim dense-mode
 ip igmp helper-address 34.1.1.3
 duplex auto
 speed auto
end

We will start getting reply on R1