3Com 8807 Configuration Manual page 472

472 C 44: PIM-SM C
HAPTER ONFIGURATION
[3Com-vlan11] quit
[SW8800] interface vlan-interface 11
[3Com-vlan-interface11] igmp enable
[3Com-vlan-interface11] pim sm
[3Com-vlan-interface11] quit
[SW8800] vlan 12
[3Com-vlan12] port ethernet 2/1/6 to ethernet 2/1/7
[3Com-vlan12] quit
[SW8800] interface vlan-interface 12
[3Com-vlan-interface12] igmp enable
[3Com-vlan-interface12] pim sm
[3Com-vlan-interface12] quit
n
You should enable PIM-SM on all equal-cost routes if there are any.