Multicast Forwarding Mode Incorrect Due to Multicast Service Fault
This topic describes how to solve the fault multicast forwarding mode incorrect due to multicast service unavailable of the MA5800.
Fault Type
Multicast service
Keyword
Multicast unavailable
Fault Description
When the user VLAN is the same as the multicast VLAN, the multicast service is normal; however, when the user VLAN is different from the multicast VLAN, the multicast service is unavailable, but the multicast subscribers are online.
Cause Analysis
- The data configuration is incorrect, because the unicast service is normal but the multicast service is unavailable.
- The setting of the VLC software is incorrect.
- The join packet fails to reach the multicast server, or the server does not respond normally.
- Certain security functions are enabled. As a result, the packets are intercepted.
Procedure
- The multicast service is normal when the user VLAN is the same as the multicast VLAN. Therefore, it can be determined that the device can implement the multicast service. In addition, the multicast subscribers are online when the multicast service is normal. Therefore, the multicast service of the device is normal.
- Modify the user VLAN, and modify the multicast configuration data accordingly. It is found that the multicast subscribers are online, but the multicast program is not available on the PC that functions as the multicast client. Then, modify the user VLAN to be the same as the multicast VLAN. The multicast service returns to the normal state. Therefore, it can be determined that the setting of the VLC software is correct.
- Capture packets on the PC that functions as the multicast client. It is found that no multicast packet is received. Then, capture packets on the PC that functions as the multicast server. It is found that the multicast packets are transmitted from the server.
- Based on the preceding two situations, it can be determined that the multicast media packets are discarded on the way from the OLT to the ONU. Then, mirror the PON port and capture packets. It is found that the media packets are issued. Therefore, the media packets are discarded on the ONU side.
- It is known that the protocol packets and the media packets are transmitted through different channels, that is, through different GEM ports. For ONU that does not have the VLAN conversion function, the media packets still carry the multicast VLAN tag when reaching the user port, and therefore the user port discards the data packets whose VLAN is different from the native VLAN of the user port on the ONU. Therefore, the PC (multicast client) cannot receive the multicast media packets, which causes the failure of the multicast service.
- Run the ONT multicast-forword tag translation command to modify the multicast forwarding mode of the ONU to translation. The multicast service returns to the normal state.
Suggestion and Summary
For ONU that does not have the VLAN conversion function, the multicast service is implemented on the ONU in the following three ways:
- The user VLANs and the multicast VLAN are the same (not recommended when the broadcast domain is large because of the large number of subscribers).
- All user VLANs are the same, but are different from the multicast VLAN. In this case, the multicast service is implemented by setting the multicast forwarding mode.
- A switch is connected to the ONU to remove or convert the VLAN tag. With the capability of the switch, the multicast service can be implemented for multiple subscribers and multiple VLANs concurrently.
