I am trying to configure some PC6248s for Multicast/IGMP and I think I found a solution but I'm not sure why it works, and why it works better than the old configuration I started with.

My network is setup as shown.

Plain Cheap Router --> Cisco Switch --> PC6224 --> [PC6248(1) --> PC6248(2)]

  |--> Cisco 300

There is all sorts of multicast traffic distributed along the network, but the part I am interested in are only the devices attached to the 6248s.  I have two units, one is a multicast receiver (call this R1), the other is 4 receivers and a transmitter in one unit (call this RT1).  Receiver, R1 is trying to join the group for transmitter RT1.

The configuration I started with is given below. All ports are configured the same way.  The switches are connected via port 5 on both switch (the real setup will use a fiber link on one of the xg# Ports).  This configuration works most of the time.  It doesn't work though when I have the upstream network and RT1 connected to PC6248(1) and R1 connected to PC6248(2).  The receivers on RT1 get their traffic just fine, but receiver on R1 cannot join the group for the RT1 transmitter.

PC6248(1) and (2)

configure
vlan database
vlan  999
ip igmp snooping 999
ip igmp snooping maxresponse 999 1
ip igmp snooping querier 999
ip igmp snooping querier election participate 999
exit
stack
member 1 1
exit
ip address 192.168.2.9 255.255.255.0
ip address vlan 999
interface vlan 999
bridge multicast forbidden forward-unregistered
exit
ip igmp
username "admin" password xxxxxxxx level 15 encrypted
bridge multicast filtering
ip igmp snooping
ip igmp snooping querier
ip igmp snooping querier address 192.168.2.9
ip igmp snooping querier query-interval 20
!
interface ethernet 1/g1
ip igmp snooping
ip igmp snooping leave-time-out 1
switchport access vlan 999
exit
!

...... ..... ..... 
interface ethernet 1/xg4
ip igmp snooping
ip igmp snooping leave-time-out 1
switchport access vlan 999
exit
exit

In trying to get this to work all of the time I started messing with the IPv4 Multicast settings and Routing settings.  I have a setup that seems to work, I just don't know why it works.

The setup is the exact same, and the configuration is below. I only made the changes to a few ports: 5, 17, 25, 47; all others ports are the same as above.

PC6248(1)

configure
vlan database
vlan 123,999
ip igmp snooping 999
ip igmp snooping maxresponse 999 1
ip igmp snooping querier 999
ip igmp snooping querier 999 address 192.168.2.9
ip igmp snooping querier election participate 999
vlan routing 123 1
exit
stack
member 1 2
exit
ip address 192.168.2.9 255.255.255.0
ip address vlan 999
interface vlan 123
routing
ip address 172.20.254.12 255.255.0.0
bandwidth 10000000
ip local-proxy-arp
ip mtu 1500
exit
interface vlan 999
bridge multicast forbidden forward-unregistered
exit
username "admin" password xxxxx level 15 encrypted
bridge multicast filtering
ip igmp snooping
ip igmp snooping querier
ip igmp snooping querier address 192.168.2.9
ip igmp snooping querier query-interval 20
ip igmp snooping querier timer expiry 100
ip multicast

!
interface ethernet 1/g1
ip igmp snooping
ip igmp snooping leave-time-out 1
switchport access vlan 999
exit
!

..... ..... .....
interface ethernet 1/g4
ip igmp snooping
ip igmp snooping leave-time-out 1
switchport access vlan 999
exit
!
interface ethernet 1/g5
ip igmp snooping
ip igmp snooping leave-time-out 1
switchport access vlan 123
exit
!
interface ethernet 1/g6
ip igmp snooping
ip igmp snooping leave-time-out 1
switchport access vlan 999
exit
!

..... ..... .....
interface ethernet 1/g16
ip igmp snooping
ip igmp snooping leave-time-out 1
switchport access vlan 999
exit
!
interface ethernet 1/g17
ip igmp snooping
ip igmp snooping leave-time-out 1
switchport access vlan 123
exit
!
interface ethernet 1/g18
ip igmp snooping
ip igmp snooping leave-time-out 1
switchport access vlan 999
exit
!

..... ..... .....
interface ethernet 1/g24
ip igmp snooping
ip igmp snooping leave-time-out 1
switchport access vlan 999
exit
!
interface ethernet 1/g25
ip igmp snooping
ip igmp snooping leave-time-out 1
switchport access vlan 123
exit
!
interface ethernet 1/g26
ip igmp snooping
ip igmp snooping leave-time-out 1
switchport access vlan 999
exit
!

..... ..... .....
interface ethernet 1/g46
ip igmp snooping
ip igmp snooping leave-time-out 1
switchport access vlan 999
exit
!
interface ethernet 1/g47
ip igmp snooping
ip igmp snooping leave-time-out 1
switchport access vlan 123
exit
!
interface ethernet 1/g48
ip igmp snooping
ip igmp snooping leave-time-out 1
switchport access vlan 999
exit
!
..... ..... .....
interface ethernet 1/xg4
ip igmp snooping
ip igmp snooping leave-time-out 1
switchport access vlan 999
exit
exit

PC6248(2)

All ports are configured the same, the only difference is the beginning of the config.

configure
vlan database
vlan 123,999
ip igmp snooping 999
ip igmp snooping maxresponse 999 1
ip igmp snooping querier 999
ip igmp snooping querier 999 address 192.168.2.8
ip igmp snooping querier election participate 999
exit
stack
member 1 2
exit
ip address 192.168.2.8 255.255.255.0
ip address vlan 123
interface vlan 999
bridge multicast forbidden forward-unregistered
exit
username "admin" password xxxxx level 15 encrypted
bridge multicast filtering
ip igmp snooping
ip igmp snooping querier
ip igmp snooping querier address 192.168.2.8
ip igmp snooping querier query-interval 20
ip igmp snooping querier timer expiry 100

There is probably a much better way to do this, but this is what I managed to come up with. If you have any insight into why the config with routing works better I would really like to hear it. And if you have any recommendations on a better configuration those would be appreciated to.

Thank you