3750 multicast flood in source vlan

[smirnov.pavel]

I have issue with following configuration:

two ports in same vlan. Multicast traffic received over one of interfaces got flooded to second one.

Sample config:

interface GigabitEthernet1/0/20
 switchport trunk encapsulation dot1q
 switchport trunk allowed vlan 10,15
 switchport mode trunk
!
interface GigabitEthernet2/0/20
 switchport trunk encapsulation dot1q
 switchport trunk allowed vlan 10,15
 switchport mode trunk
!
interface Vlan10
 ip address 10.1.1.1 255.255.255.252
 ip pim sparse-dense-mode
 no ip mroute-cache
!

Here I receive multicast data over g2/0/20 and it gets flooded out of g1/0/20. Though all receivers are in separate vlans, not in vlan10. IGMP snooping is on and sh ip igmp membership doesn't list any of these interfaces.

Thanks.

[lgijssel]

Your expectation is only true for access ports. Multicasts are always flooded over trunk interfaces.

Reason for this is there may be other receivers on downstream switches behind g1/0/20.

regards,

Leo

[smirnov.pavel]

Thanks.... Can you point me to appropriate cisco docs?

An what you can advise me in doing here? The problem is that I need to receive multicast from both interfaces in vlan 10 but for different groups and I don't want to have all data I receive over one link to get flooded to another one. Also seems I have no way to get rid of trunk here...