R7#sh run | b ip mu
ip multicast-routing   <---------- on all routers
ip audit po max-events 100
!
interface FastEthernet0/1
 ip address 17.100.1.2 255.255.255.0
 ip pim sparse-dense-mode  <-------------- on all routers except R4
 duplex auto
 speed auto
!
R4#sh run int fa 0/0
Building configuration...

Current configuration : 163 bytes
!
interface FastEthernet0/0
 ip address 180.40.7.130 255.255.255.224
 ip nat inside
 ip pim dense-mode
 ip igmp join-group 224.4.4.4
 duplex auto
 speed auto
end