Unanswered Question
Feb 27th, 2008

I have heard someone before talking about layer 2 broadcast, am i right in saying there is no such thing ?

I have this problem too.
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carl_townshend Wed, 02/27/2008 - 05:31

is this called a layer 2 or 3 broadcast then, would this be a normal lan broadcast? i thouht its destined for the subnet, and not the mac address,

please explain

carl_townshend Wed, 02/27/2008 - 05:46

so what kind of traffic is normal on my network, layer 2 or 3 broadcast? if its a layer 3 broadcast, does it change the destination mac also? and if we do have layer 2 broadcasts, are these still broken up by vlans


Hi Carl

As your network will be operating at both layer 2 and layer 3 (all your hosts have IP addresses) then layer 2 and layer 3 broadcasts will be seen and are normal.

A good example of a layer 2 broadcast is an ARP request.

A subnet level (layer 3) broadcast will be sent to the broadcast IP address of the subnet.

e.g. On the subnet the broadcast IP address is

An all host (layer 3) boradcast will be sent to the destination IP address This is for example the destination address that a DHCP discover message is sent to.

Yes, when you create VLAN's you create individual broadcast domains. Each VLAN is a broadcast domain.

Scotts article gives a really good explanation.

Best Regards,


carl_townshend Wed, 02/27/2008 - 06:14

when you say all host broadcast, what is this, is this not the same as a subnet broadcast, if I have 2 networks say and if i sent a broadcast to, would they both receive it ?


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