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switch behaviour on multicast packet

hello sir,

Please help me describe what will switch manageable do when receipt multicast packet ??

 

let say i have 8 port switch contain 1 vlan

will switch forward all packet at all port

thank you :)

1 ACCEPTED SOLUTION

Accepted Solutions

Jon Marshall
VIP Community Legend VIP Community Legend
VIP Community Legend

It depends on quite a few things.

If you are talking about traffic with a vlan, ie. no multicast routing, then by default managed switches have IGMP snooping enabled. 

With just that enabled it seems to be dependant on the switch platform ie. some platforms will send the multicast packet out of all ports except the one it was received on and some will not forward the multicast packet.

Note even if it is forwarded it is in effect treated as broadcast.

If you want it to be sent to only the devices that want it or if your platform behaviour is not to forward the packet then you need to enable the "IGMP snooping querier" function on your switch.

If you did enable multicast routing then you would also enable PIM on the L3 vlan interface and then you wouldn't need the querier function but you would still need IGMP snooping.

Jon

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1 REPLY 1

Jon Marshall
VIP Community Legend VIP Community Legend
VIP Community Legend

It depends on quite a few things.

If you are talking about traffic with a vlan, ie. no multicast routing, then by default managed switches have IGMP snooping enabled. 

With just that enabled it seems to be dependant on the switch platform ie. some platforms will send the multicast packet out of all ports except the one it was received on and some will not forward the multicast packet.

Note even if it is forwarded it is in effect treated as broadcast.

If you want it to be sent to only the devices that want it or if your platform behaviour is not to forward the packet then you need to enable the "IGMP snooping querier" function on your switch.

If you did enable multicast routing then you would also enable PIM on the L3 vlan interface and then you wouldn't need the querier function but you would still need IGMP snooping.

Jon

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