Multicasting

Unanswered Question
Jun 2nd, 2009

Hi All,

Users are accessing streaming application from the internet for training purpose. We have internet links in the data center and users are using proxy server to access internet.

Internet links are connected in Router 3845, core switches are C6509 & access switches C2960.

Our requirement is to configure multicasting to reduce bandwidth while using the webcast application.

In this scenario which one is preferred PIM SPARSE or PIM DENSE mode? Is any thing need to configure in L2 switches?

Thanks in advance

Regards,

Pradeep

I have this problem too.
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Giuseppe Larosa Tue, 06/02/2009 - 04:47

Hello Pradeep,

I recommend to use ip pim sparse mode.

You need to use one core router as the rendeves-point.

Use a loopback address advertised in your internal routing protocol for this

all other routers/multilayer switches need

ip multicast-routing

ip pim sparse-mode on all interfaces

+ in global config

ip pim rp-address

L2 LAn switches should be fine with default configuration.

You should check if they are configured for IGMP snooping.

Edit:

for more details see

http://www.cisco.com/en/US/docs/ios/ipmulti/configuration/guide/imc_basic_cfg_ps6350_TSD_Products_Configuration_Guide_Chapter.html#wp1054581

Hope to help

Giuseppe

pradeepkum Tue, 06/02/2009 - 05:18

Thanks Guiseppe

Is it ok to configure the router C3845 as the rendeves-point which is connected to the internet link?

In this scenario what would be the source of mulicast? The proxy server in our network or the server in internet that host the web application? Because user request will hit the proxy server for any request.

Regards,

Pradeep

Giuseppe Larosa Tue, 06/02/2009 - 20:51

Hello Pradeep,

the presence of the proxy requires some more thoughts.

Using the C3845 facing the internet can be fine.

About the source: the suggested configuration for IP PIM sparse-mode is not source specific (SSM) so whatever is the source all flows with the same G multicast group are treated in the same way.

I think the result of this would be that multicast traffic would bypass the proxy with conventional PIM Sparse mode.

if this is not acceptable for your security policy the solution needs more complexity:

Usage of Source Specific Sparse Mode (SSM) and/or the use of two multicast domains should be considered.

Hope to help

Giuseppe

pradeepkum Tue, 06/02/2009 - 23:04

Hi Giuseppe,

This setup I told you is in our head office which is connected to 30 different branches through Point to Point leased lines in Hub & Spoke design. For redundancy in another branch we have internet link connected with C3845 ROUTER 2. We are doing load sharing in these internet link.

So configuring one C3845 as RP will work or need to do any changes?

One last query: Sometime from any one of the branch itself (intranet) we will do webcast. At that time shall I configure the RP router which is near to the server that does the webcast?

I need to achieve multicasting for both internet and intranet. Kindly help me to design this.

Regards,

Pradeep

Giuseppe Larosa Tue, 06/02/2009 - 23:25

Hello Pradeep,

>> Sometime from any one of the branch itself (intranet) we will do webcast. At that time shall I configure the RP router which is near to the server that does the webcast?

This is not necessary but the PIM topology has to be complete: the source PIM router builds a spanning-tree towards the RP.

Intranet multicasting with a complete topology (pim enabled on all involved links and routers) is not a problem and it is standard configuration.

As I wrote before interaction with proxy has to be considered.

I will try to look for case studies involving multicast and internet proxy.

If it is possible for you you may attach a network diagram (jpeg format) to see what is the position of the proxy.

Hope to help

Giuseppe

pradeepkum Tue, 06/02/2009 - 23:36

Thanks for your help Giuseppe

I will upload the network diagram tomorrow with necessary details.

Regards,

Pradeep

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