Recommended broadcast domain size

[Kobra09]

Hi,

I read somewhere that the IEEE recommended size of a broadcast domain in an enterprise network application is /22, however I cannot find that particular document when searching around. Can someone please share the link to the said document if someone knows about it? Thanks a lot in advance. 

[MHM Cisco World]

WoW it so big
there are 1024 user connect to this subnet, 
how many SW serve this domain?

[Kobra09]

At the moment, about 16 switches in total.

And the VLAN size in production is much bigger right now. Tried to ask help here in the community so we can try to redesign considering the inputs here.

[Flavio Miranda · Accepted solution]

Hi

 It is really hard to believe that IEEE said that. To me this is more like hearsay. I have a copy of the 802.3 standard here and I failed to find it. And honestly I dont believe they said. Because broadcast domain size is a matter of design and IEEE does not teach how to design, they describe how the technology works.

 If you have devices that talk too much, you better narrow your network segment. If you have devices that is silient, you dont need to worry much. And there´s no magic number. Just try to keep is as smaller as possible.

[Kobra09]

Edit: My post should have said 'recommended maximum size of a broadcast domain'

Thanks for your reply! Will surely take note of this. I looked it up as well in the 802.3 and i got dizzy trying to find it.

[Joseph W. Doherty · Accepted solution]

I don't know of any IEEE recommendation, but a /22, in a "typical" shared media host environment, like on switched Ethernet, might "safely" go as large as a /22.

What's really important is how much broadcast traffic there is, also how much of it is "needless" to most hosts.

One VoIP vendor's equipment I worked with, recommended a /24 for VoIP phones and PCs on same port but in voice and data VLANs, and up to a /23 for VoIP phones on their own ports in their own VLAN.  The latter, then, recommends allowing twice as many VoIP phones in the voice VLAN because although, in both cases, the PCs are not in voice VLAN, on the shared ports, their broadcasts will still be sent out the shared ports.

For wireless, I recommended and we used /20s, worked just fine, but different technology than wired Ethernet.

[Kobra09]

Thanks! Will share these insights to our network design, it's great to receive valuable responses and info from you all.