Multicast ASM vs Anycast

Hi, is the terminology 'ASM' (Any Source Multicast) the same as 'Anycast' - reading through various material at the moment to get my head around it.




  • No, it is not the same. But Anycast is often used in PIM ASM networks


    ASM refers to the source of the multicast stream, usually a playout server.

    ASM model does not care about the source of this stream - the client requests a multicast stream from any server.

    As opposed to SSM where the client will request the multicast stream from spesific server.


     Anycast refers to using the same IP for a service. This is for reaching where the service will be closest (as seen from the network). With regards to Multicast this is usually for making redundant PIM RP. Two RP's can then share the same Anycast IP. These two RP's need to exchange PIM information by using MSDP. 

  • Hi Dominic,

    As far as I understand, we have two modes in multicasting, ASM & SSM. In ASM mode, there can be any source that has not been defined manually which needs an RP to find the source of multicast. In SSM mode, source address is mapped with the group address & IGMPv3 is used in order for host membership. It doesn't require any RP address due to the static mapping configuration.



  • Thanks guys, it was the terminology that got me.  I think the key was this phrase:


    'Two RP's can then share the same Anycast IP'


    I get the SSM vs ASM, with SSM having a pre-programmed multicast source (like a sky box) and ASM using a shared tree with RP, I just wasn't sure what 'Anycast' meant.  But now you say that an 'Anycast IP' is a shared IP/same IP between different RP's it's cleared it up.



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