6509 core switch command, ip pim sparse-dense-mode

[Horacio Gutierrez]

Hello,

What is PIM?  Can you please give me an example when I will use and not use the PIM command.

Thanks.

[Shashank Singh]

Hi Horacio,

PIM or protocol independent multicast is used for routing multicast traffic among L3 domains. You need to use PIM if  want your multicast traffic to be routed from one vlan to another, for eg.

You do not need PIM if you want multicasting in just one L2 domain (vlan). In such scenarios, igmp snooping is used.

HTH

Shashank

[nkarpysh]

Hi

PIM is Protocol Independent Multicast - the way routers/switches can effectively route MCAST through your network. Several modes of it can be used like Sparse, Dense or mixed one. All different in the path MCAST takes from server to end client.

So Basically that is used for multicasting. PIM is used to enable particular L3 interface to participate in MCAST routing and appear in mroute table. Without those commands and ip multicast routing enabled on the switch it would treat MCAST as broadcast and will not use all advanategs of Sparse/Dense/Both modes.

There is one more thread on the command you mentioned in subj - pls check if that answers your question

https://supportforums.cisco.com/thread/145759

Not sure what is your IOS but this is the command guide explaining that in more details:

http://www.cisco.com/en/US/docs/ios/12_3/ipmulti/command/reference/ip3_i2g.html#wp1080424

Hope this helps,

Nik

[Horacio Gutierrez]

Hello Nikolay,

When you refer to multicast what kind of devices would create a mulitcast can you give me some examples.  Also what is the difference between Sparde, Dense, Mixed  mode?

Thanks a lot

[nkarpysh · Accepted solution]

Hello,

Multicast is traffic stream set to a group of host while regular unicast is sent between two host. Mcast is also different from broadcast as the last sent to all and Mcast can limit the group of receivers.

Mcast is sent to a wellknown group of ip addresses 224.0.0.0 to 239.255.255.255. Stream is sent by special server. Examples of mcast in network are digital radio or video streams.

You can check more about it

http://en.wikipedia.org/wiki/Multicast

Regarding the different modes of mcast operation you can read here:

http://www.cisco.com/en/US/partner/tech/tk828/technologies_tech_note09186a0080094821.shtml

Hope this is helpfull.

Nik