When the users of the MA5600T are watching IPTV programs, blank screen occurs two or three minutes later. Screen display recovers to normal if the users switch to another channel; however, blank screen recurs two or three minutes later. The IPTV users of the MA5600, however, do not have this problem.
1. MA5600(config)#debugging igmp all
2. MA5600TM#(config)debugging igmp port 0/19/0
3. Perform mirroring and packet capture on the upstream port of the MA5600T.
4. Enable the unsolicited reporting capability of multicast programs on the MA5600T. In this way, the IGMP packets will be exchanged frequently. Enable or disable this capability according to actual network resources and device performance. MA5600TM(config-mvlan4)#igmp program modify ip 126.96.36.199 unsolicited enable
5. Enable the static attribute of the multicast subtend users on the MA5600T. In this way, after a program is demanded by users, this program will be online all the time even if the leave packet is received.
MA5600(config-btv)#igmp cascade-port modify 0/7/0 static enable
MA5600(config-btv)#igmp static-join cascade-port 0/7/0 ip 188.8.131.52
When this cascading port is statically added to a program group, the report packet and leave packet will be dropped. In this case, the quick leave attribute of the cascading port does not take effect. In this way, the multicast stream of the program will be led to the multicast cascading port, thus reducing the interaction of packets. Then the user of the lower-layer subtended device can quickly demand programs, but the bandwidth of the upper-layer device may be occupied continuously. Enable or disable this attribute according to actual conditions.
It is recommended that you learn the differences in the implementation of the multicast service on the MA5600 and the MA5600T. When a fault is related to device compatibility, note that the impact on network resources and on device performance should be considered.
The IGMP users of the MA5600 are watching normal programs all the time, which indicates that the program streams are normal. Then, it can be determined that the fault occurs on the MA5600T.
1. The IGMP users of the MA5600T can go online in the normal state, which indicates that the basic multicast cascade configurations and the configurations of multicast programs and IGMP users of the MA5600T are normal.
2. A user of the MA5600T can watch a program for only two to three minutes and then blank screen occurs. Then, it can be determined that the IGMP user sends the leave packet itself and then it goes offline, or the user is online all the time but the program stream is interrupted. The later case seldom occurs unless the line is disconnected. In general, the fault symptom is a failure in demanding a program, or blank screen occurs immediately after the program is displayed, instead of two or three minutes later. The third cause is that the user goes offline abnormally.
3. Run the debugging igmp command to enable the debugging function globally on the MA5600 and for a certain service port on the MA5600T respectively to check the interaction of IGMP protocol packets.
4. It is found that the MA5600 transmits the IGMP query packet, but does not receive the IGMP report packet of the corresponding program. Therefore, the MA5600 considers that the IGMP user does not respond after time 2 × General query interval(s) + General query response time(0.1s), and then deletes the corresponding multicast forwarding entry.
5. Then, it can be determined that the MA5600T does not transmit the IGMP report packet. Run the debugging igmp command on the MA5600T to check the debugging information. It is found that the multicast upstream port does not receive the IGMP query packet of the corresponding program from the MA5600.
6. The MA5600 has already transmitted the IGMP query packet but the MA5600T does not receive it. Where is the IGMP query packet lost?
7. Perform mirroring and packet capture on the upstream port of the MA5600T to check the interaction of the IGMP protocol packets.
8. The analysis of captured packets shows that the IGMP query packet is already transmitted from the MA5600 to the MA5600T, and already reaches the upstream port of the MA5600T. Because this packet is an untagged packet, the VLAN ID of PVID is added to it when it reaches the upstream port of the MA5600T. In general, the VLAN ID of PVID is different from the multicast VLAN ID. As a result, the IGMP query packet will not be transmitted to the multicast module of the MA5600T for processing, and then cannot reach the IGMP user. Consequently, the IGMP user will not respond with the IGMP report packet.
9. Why the IGMP users of the MA5600T can demand programs successfully? This is because that the IGMP report packet transmitted by the MA5600T carries the multicast VLAN ID, but the MA5600 determines the IGMP packet according to whether the DMAC is the IGMP MAC address, instead of whether the packet is a tagged or untagged packet. If the DMAC is the IGMP MAC address, the packet is transmitted to the multicast module of the MA5600 for processing.
10. Because the MA5600 does not support M-VLAN (multicast VLAN), the IGMP packets transmitted from the MA5600 do not carry a VLAN tag. The MA5600T, however, supports M-VLAN since V8R5. Therefore, the VLAN ID of the multicast packets that enter the MA5600T must match the M-VLAN ID and then the packets can be processed in the specified M-VLAN.
11. When the aging time of the IGMP user expires, the MA5600 considers that the user already goes offline, and then deletes the corresponding entry to disconnect the multicast stream.