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S12704 multicast service did not work

Publication Date:  2017-12-29 Views:  487 Downloads:  0
Issue Description

The topology just as below:

The S12704 as the core switch,one of the S5720 connect the multicast source, the other S5720 connect the receiver.

The three switch connect with VLAN 2020, it running the routing protocol is the OSPF.

The multicast source unicast routing and the receiver routing released through the OSPF.

The multicast routing protocol is the PIM-SM, the S12704 as the static-rp.

It running the PIM-SM on the VLANIF2020 which is used to connect the three switch.

The PIM neighbor have been established, the S12704 can learn the multicast routing from the source switch.

But the receiver switch can't learn it, the service can't work.


Handling Process

We checked the configuration of the switch found that PIM-SM running in the VLANIF 2020 which is also used to connect the three switch.

Then we checked it with the expert that the Layer3 multicast routing can't forward on the same VLANIF.

There have two way to solve this issue:

1. Change the VLAN which used the different VLAN to connect the switch then running the PIM-SM

2. Enable the Layer2 multicast on the three switch.

After the customer enable the Layer2 multicast on the VLAN2020, the receiver switch can learnt the multicast routing.

But the receiver still can't watch the video from the source, then we capture the packet from the interface which connect the source.

we found that the source packet TTL valve is one, just as below:

so the receiver can't receive the source.

After the customer change the configuration of the source, the issye is solved.

Root Cause

There have two reason about this issue:

1.the same VLAN (network segment) cannot provide pure Layer 3 multicast forwarding

2. the VLC player  TTL value can't been set as one


1. For the switch, if used the same VLAN, it need to enable the Layer2 multicast; if used the different VLAN, you can configure the Layer3 multicast routing.

2. The multicast source packet TTL can't set as one.