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Community Member

Multicast troubleshooting

He everyone,

I am new to multicast and have a question regarding receiving the multicast. what is the easiest way to figure out if the data is being sent by the source or not. Any tips will be a big help.

Regards

1 ACCEPTED SOLUTION

Accepted Solutions
Bronze

Re: Multicast troubleshooting

Hello,

To troubleshoot multicast, I have found the "show ip mroute count" command is a good place to start.

When you do this command, you will see the multicast groups, and statistics for the source address - which you mention you want to check.

Looking at the line beginning with "Source", you can see the forwarding statistics for the group. They are separated by "/" and are as follows:

Sent Packet Count/Packets sent per second/Avg Pkt Size/Kilobits per second

An example is below:

show ip mroute count

IP Multicast Statistics

2 routes using 1714 bytes of memory

1 group, 0.50 average sources per group

Forwarding Counts: Pkt Count/Pkts per second/Avg Pkt Size/Kilobits per second

Other counts: Total/RPF failed/Other drops(OIF-null, rate-limit etc)

Group: 224.12.12.12, Source count: 1, Packets forwarded: 4, Packets received: 4

Source: 10.1.1.4/32, Forwarding: 4/1/100/0, Other: 4/0/0

7 REPLIES
Bronze

Re: Multicast troubleshooting

Hello,

To troubleshoot multicast, I have found the "show ip mroute count" command is a good place to start.

When you do this command, you will see the multicast groups, and statistics for the source address - which you mention you want to check.

Looking at the line beginning with "Source", you can see the forwarding statistics for the group. They are separated by "/" and are as follows:

Sent Packet Count/Packets sent per second/Avg Pkt Size/Kilobits per second

An example is below:

show ip mroute count

IP Multicast Statistics

2 routes using 1714 bytes of memory

1 group, 0.50 average sources per group

Forwarding Counts: Pkt Count/Pkts per second/Avg Pkt Size/Kilobits per second

Other counts: Total/RPF failed/Other drops(OIF-null, rate-limit etc)

Group: 224.12.12.12, Source count: 1, Packets forwarded: 4, Packets received: 4

Source: 10.1.1.4/32, Forwarding: 4/1/100/0, Other: 4/0/0

Re: Multicast troubleshooting

hi Mehdi,

Michael has provided good information to you. Just add other information.

Other counts: Total/RPF failed/Other drops(OIF-null, rate-limit etc)

Other: 4/0/0

If you're experiencing with RPF Failure then this command can show you.

Please check this link out:

http://www.cisco.com/en/US/tech/tk828/technologies_tech_note09186a0080093f21.shtml

Toshi

Community Member

Re: Multicast troubleshooting

Great!! Thank you. In sparse mode,If I have a receiver trying to join the group, then I should see the count increase which means that the source is sending the stream for that particular group. If I don't see the count increase which will mean that the the source is not sending the stream for that group. Correct? Also, if I am in sparse mode, and have a receiver on my side, what will this indicate (*,g) & (s,g)?

Thanks again.

Cisco Employee

Re: Multicast troubleshooting

Mehdi,

There is a few things to consider.

- What is your topology like?

- Do you see the source (s,g) on the RP?

- Do you see that there is a receiver (*,g) on the RP?

Regards

Harold Ritter
Sr. Technical Leader
CCIE 4168 (R&S, SP)
harold@cisco.com
México móvil: +52 1 55 8312 4915
Cisco México
Paseo de la Reforma 222
Piso 19
Cuauhtémoc, Juárez
Ciudad de México, 06600
México
Community Member

Re: Multicast troubleshooting

Topology is that I have two routers receiving the stream. I do have receiver trying to join the group and do see (*,g). In some stream is working fine and I do see the (s,g) but the others I only see (*,g). I did the ip mroute count and I see no packets and I even tried to do ip igmp join-group (Group ip) and still no luck. I think I am not receiving the group from the source just making sure that is the case.

Thank you

Re: Multicast troubleshooting

hi Mehdi,

We have to know exactly what the topology looks like. One is working fine. Another one is not? Have you correctly configured the RP? To make sure that the RP-C is advertiseting the correct group. To make a bit more clear on what's happening. Would you please post the configuration,excluding sensitive information?

Toshi

Community Member

Re: Multicast troubleshooting

Thank you all. I think I have the answers to my problem. It sure was a great help.

Regards

Mehdi

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