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I have a doubt about packets sniffer. I read that it can sniff only in local segment and often it is referred as collision domain. But... The collision domain for a switch is each single port therefore you can only sniff your traffic. Maybe it is a broadcast domain? Thanks

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have a doubt about packets sniffer. I read that it can sniff only in local segment and often it is referred as collision domain. But... The collision domain for a switch is each single port therefore you can only sniff your traffic.

That's correct – with a switch, you will only see traffic belonging to you (plus broadcasts and multicasts).

There are a few ways around it. Many managed switches have a dedicated "Mirror port" feature (also called "SPAN") which copies someone else's traffic to you. An extension called "(E)RSPAN" allows the same across several layers of switches.

Some gray-area methods can be used, such as ARP spoofing, to trick another host into sending you the data directly.

Maybe it is a broadcast domain?

No. "Broadcast domain" only applies to traffic which actually is broadcast – most of it is not.

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Where you use a packet sniffer on a computer connected to an ethernet switch it can typically only see traffic going to and from that computer. Of-course, where that computer is a router, it gets all traffic going through it.

I don't think a "collission domain" is an appropriate term when talking about a switched network (but would apply to hubs and wifi networks).

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