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multicast

Posted on 2013-07-01
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Last Modified: 2013-07-24
I have 4 devices that send video across my network. and it seems that I have a broadcast storm across all of my VLANs. I have enabled igmp snooping and ip pim dense-mode command. But it does not seem to work. I am not a multicast guy. But any inputs will be greatly appreciated.
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Question by:leblanc
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by:Don Johnston
ID: 39289988
Do you have multiple networks or VLANs?

How is the video stream transmitted? (broadcast or multicast)?

What manufacture/model of network equipment is involved?
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surbabu140977 earned 1000 total points
ID: 39291112
Without a diagram and pasting of configs from your pim routers and switches, it will be difficult to comment. Also hardware model is required. For cisco, we always recommend CGMP.

Typically igmp snooping is known to cause flood because of config issue. People in a small network sometime do manual mapping to avoid the headache of troubleshooting igmp snooping issues. But manual mapping is not the very best for significant number of ports.

Sometimes if your application too is  not supported for igmp snooping. Whichever host responds to multicast packets first, the L2 switch maps the port for only one host mac. The other hosts running on the same port will not receive multicast creating a broadcast storm.

Best,
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by:leblanc
ID: 39291870
The devices that generate video work but it flooded the network and made the network inoperable.
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by:Don Johnston
ID: 39292040
Once again...

Do you have multiple networks or VLANs?

How is the video stream transmitted? (broadcast or multicast)?

What manufacture/model of network equipment is involved?
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Author Comment

by:leblanc
ID: 39292094
Multiple VLANs... vlan 200 is for the video device (blackbox media centro ip mtx). Video is transmitted through multicast.
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by:Don Johnston
ID: 39292608
Once again...

What manufacture/model of network equipment is involved?
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by:Don Johnston
ID: 39293803
Sorry... Routers and switches. Manufacture and model please.
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by:leblanc
ID: 39293892
2960S for the access switches and 3750 series for the core.
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by:Don Johnston
ID: 39293977
Now we're getting somewhere. :-)

Please post the configs of the switches.

I think this may be a spanning-tree issue since what you're describing sounds like a typical broadcast storm.
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by:leblanc
ID: 39294838
Let me ask you this. When I introduce a device that sends out video to a multicast IP address, do I have to configure my switches with multicast routing or any other multicast features?
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by:Don Johnston
ID: 39294904
Only if the sending device and receiving device are on different networks (VLANs).
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by:surbabu140977
ID: 39296289
Switches are layer 2 devices. Routers are layer 3 devices.

Multicast group address is L3 address. So you can understand that a switch in between will need L3 to L2 translation. Hence you need 'something' in switches to configure for multicast.

You already did 'igmp snooping' for that. It's the L2 multicast group mapping to host/port mac mapping service.

But looks like igmp snooping is not working properly (due to misconfig somewhere upstream). Hence you will need to paste configuration for all of your routers and switches.

Best,
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by:leblanc
ID: 39296981
My client would like to try ip pim sparse-mode. But when she tried to configure the RP, the 6509 does not take the command ip pim rp-address. Any idea?

There is not a lot of multicast config currently on the switch. But from the high level, my client has:

ip routing-multicast

on vlan 200:
ip pim sparse-mode
ip pim rp-address 20.20.20.1 (DID NOT WORK!!!!)

on vlan 10:
ip pim sparse-mode
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Assisted Solution

by:Don Johnston
Don Johnston earned 1000 total points
ID: 39297059
Here's the thing:

I have 4 devices that send video across my network. and it seems that I have a broadcast storm across all of my VLANs.

Forget the multicast routing. There's something happening at layer 2. You need to get that sorted out before you start trying to get multicast routed enabled.

Do you have redundant layer-2 paths in your network? Are you running spanning-tree?
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by:surbabu140977
surbabu140977 earned 1000 total points
ID: 39297082
What do you mean by "try"? I thought multicast was all about designing after understanding the data flow. It's not a fastethernet speed/duplex setting like auto/half/full that something will work.

Sparse mode and dense mode has got specific tree structure based on the network topology. A design meant for sparse mode will flood if you use dense and vice-versa.

Use "ip pim sparse-dense mode".  (to answer your question).

Multicast traffic won't work for same vlans here. You need one mrouter port so that igmp snooping works or a igmp snooping querier.

Please ask your client to read a bit about multicast first before "trying", else nothing would work.

This thread won't go anywhere I feel unless you present the complete picture. Bits and pieces of info whatever you are pasting will not help your cause.

Best,




Best,
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by:Don Johnston
ID: 39297090
This thread won't go anywhere I feel unless you present the complete picture. Bits and pieces of info whatever you are pasting will not help your cause.
Yep.
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Author Comment

by:leblanc
ID: 39297239
Sure, I will get the "big picture" in order. To answer to your questions, spanning tree is running and it is working without any problem. She has the problem when the blackbox is introduced to the network.
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by:Don Johnston
Don Johnston earned 1000 total points
ID: 39297407
Unless the amount of multicast traffic exceeds the available bandwidth, you shouldn't be seeing "broadcast storm" type behavior. Does the blackbox have multiple network connections?
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