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Multicast Deployment

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  • Multicast Deployment

    Its my assumption that my current issue is related to the cisco swithces on my network, so posting on this thread.
    We have been using a mass OS deployment software called DeployStudio for our Mac OS machines (macbooks, imacs, etc.) and it has been working well for over a year now, except that we have been using unicast to do this. I did try to setup multicast last year, but since I could not get it to work, never bothered much with it. But this time, we really would like to have this setup.
    My simple question would be what is the most basic 'switch' configuration setup that we need to have multicasting working well across vlans (at the same time, without flooding the network)
    FYI, what i have done so far:
    - setup all the proper multicasting settings on the software server and clients, as per their instructions
    - configured the 'destination' vlan with Multicast routing, enabled pim-sparse mode, igmp snooping and a ip helper-address pointing to the imaging server
    - configured the imaging server vlan with all the same as above, except for the ip helper-address

    What am I missing here?

    At the moment, two things I am confused about are the 'ip pim rp-address' and the TTL thresholds for the two vlan interfaces. Do I need to make any changes to these?

    Any help is much appreciated, since we really would like to get this working permanently. Thanks.

  • #2
    Re: Multicast Deployment

    PIM Sparse mode has to use an RP. Think of the RP as the root of the tree. The routers are the branches and the subnets are the leaves. You can configure an RP statically.

    ip pim rp-address x.x.x.x loopback 0 scope X group-list " " etc

    Typically you want to source from a loopback as its always available. Static RP is good for a small network with few sources. If you just have one source and a relativley small network than I would go that route. If not you can use Auto-RP which defines an RP and a Mapping Agent. The mapping agent is the one that distributes group to rp mappings to the client routers.

    As with all multicast implementations success will always relay on the RPF check. Basically the RPF says if I receive a multicast packet on an interface look in the unicast routing table and see what interface I would use to get back to the source. If they are both the same then the RPF check passes, if not then it fails and all multicast packets will be dropped. You can get around this with static mroutes etc but just be away that all PIM signalling protocols use the unicast routing table to resolve the RPF check. You can adjust the TTL to kind of scope the multcast boundary. You can also use the ip multicast boundary command which gives you more options.

    Multicast is a huge topic and the configurations can get very advanced.
    CCNA, CCNA-Security, CCNP
    CCIE Security (In Progress)