Version: MA5200G VRP3.30-2215 (independent of version)
Symptom: MA5200G and MA5100 provides multicast service and multicast replication locates at MA5100. Use STB dialup to receive multicast program. After the service is operated, users that watch the same channel will influench each other.
Detailed phenomenon: When one user of them with the same channel leaves, multicast service of other users end.
1. First check configuration of MA5200G and MA5100, and it is correct.
2. Capture packets between MA5100 and MA5200G or between MODEM and STB. Analyze packets and find: when one user exits multicast group, IGMP LEAVE packets of encapsulated PPPOE sent by STB transparently transmit to MA5200G with MA5100. MA5200G handles and responds encapsulated IP IGMP QUIRY packets. MA5100 does not respond it and MA5200G ends multicast traffic. The whole multicast traffic disruption occurs.
3. Configure the following at MA5200G:
igmp robust-count 5
igmp lastmember-queryinterval 5
Add the interval of IGMP LEAVE packets at MA5200G to specific inquiry packet (default is one second and change as five seconds). Add retransmission of inquiry packets and change default two seconds as five seconds. When MA5200G receives IGMP LEAVE packets, it needs 5*(5+1) =30 seconds and disrupt multicast traffic. During the period, receive IGMP LEAVE packets of the same channel will keep multicast service continuous.
4. Configure the following at MA5100:
NTV report interval: 20s
MA5100 is defaulted as 125 seconds and report IGMP REPORT packets to online users at MA5200G. It will report in every 20 seconds and it is within inquiry interval atMA5200G 5*(5+1)=30. Even if other user exits multicast group and MA5200G disrupts multicast traffic, it can receive IGMP REPORT packets of users.
5. Change and test, and user service is normal.
It is related with multicast handling of MA5200G and MA5100. MA5100 uses PROXY to open multicast service. MA5100 cannot handle encapsulated PPPOE IGMP packet. As a result, when one user of multicast group exits the program, IGMP LEAVE packets will transparently transmit to MA5200G. MA5200G will handle them and transmit specific inquiry packets. And MA5100 uses PROXY and not handle specific inquiry packets flooded by MA5200G and discard them directly. When MA5200G has two inquiry and no respond, it will disconnect corresponding multicast traffic and service disruptions occur.