nat routers

Discussion in 'hardware' started by guest, Feb 5, 2009.

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  1. guest

    guest Guest

    I started to learn about ip multicast even if I don't use it...

    So, mu computers are connected to a nat router so they are on the same lan. The router can deal with multicast traffic but I disabled it...

    If I understand how it works, let's say I want to use a kind of web tv application that uses multicast, my computer sill want to send an igmp packet to the appropriate "router/server" of my ISP (more of a router...) This packet will say to that router that my computer want to receive the multicast stream of a particular ip (multicast address). So the router will send them to my computer until my program send another igmp packet to say to the router that I don't want to be a part of that multicast group anymore.

    Now, for my personal nat router... If I understand, the router will see that I want to be a part of a multicast group (by listening to IGMP traffic) and will redirect the traffic that will come to it to the good computer (my computer and not the others...)
    If I disable the multicast option in my router, the router won't care about IGMP packets and will simply drop all those packets.

    Am I right?

    Also... What if my computer wants to send a multicast packet? I know some networking stuff uses multicast packets (like llmnr on vista) to do name resolution on the lan. Now, if it does this, all the computers on the lan will receive the packet and maybe answer to it... But the router will also receive this multicast packet! What will it do with it? I think it will drop it because it can't sent a multicast or broadcast packet on the wan side. Am I right??

    And If I understand how multicast works, well... It is used on lans but it can't be really used on the internet unless the ISP uses it for a tv or that kind of service right??

    Thanks for helping me

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