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Broadcast Domains

On average, how many PC's or devices should there be in a broadcast domain to main a healthy LAN network.

Hall of Fame Super Blue

Re: Broadcast Domains

Hi Nicholas

That is a bit of an open ended question really and you may get many different answers. A lot depends on how may of your applications that you run on your network rely on braodcast traffic.

Generally speaking, and it is generally, a Class C ie /24 would be the biggest. We use /25's here where i work which allows 126 hosts per subnet.




Re: Broadcast Domains

I agree with John a /24 is a comfortable size subnet which we have used for years and it makes for a very stable network environment and good response for all users .

Re: Broadcast Domains

I'll go along with that too, although it really depends how active the hosts are, and how paranoid is the NetAdmin.

Me, I'm known as the broadcast police 'cos I watch the background traffic like a hawk, and stomp on any machine that is not behaving. That way I can get away with well over the 250 or so devices a Class-C can offer. But I wouldn't recommend that to anyone else unless they are prepared to keep a close watch on the network.

I find a background noise of about 40 packets per second just about the limits of acceptability. It's an interesting exercise. Configure a switchport as access on the VLAN you are interested in, connect a network monitor to an unused NIC and collect packets for an hour or so. Most should be ARPs, some might be non-IP multicasts like CGMP (Ugh!), and maybe 1% will be flooded unicasts. Some will be stuff you really were not expecting unless you do this exercise regularly.

Kevin Dorrell


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