Recommended hosts per VLAN

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Feb 5th, 2009
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I'm looking for a Best Practice guide that describes how many hosts are recommended per VLAN..

Maybe there are differences in "normal" hosts and "broadcast-intensive" hosts...



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Edison Ortiz Thu, 02/05/2009 - 06:28
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The common design is to use /24 for LANs and /30 for point-to-point WAN/LAN links.

With that said, the subnet allocation is often driven by business requirement. For instance, if you create a server Vlan and the business requires to only have 13 servers on that Vlan, you aren't going to waste a /24 on it, do you?

Same can be said if the business has 300 servers and want all servers in the same Vlan, you need something bigger than a /24.




remco.gussen Thu, 02/05/2009 - 06:44
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Hmm. I Know that.. If you are using a private address space, it doesn't matter to use a /24 for 13 servers...

Was just wondering if there were "hard" numbers of hosts by best practice.

If you have a group of 600 student computers, are you going to create one, big /22 subnet ? I think it is better to create 3 / 24 networks, or one /23 and one /24. Broadcast domains stay small in this way...

Tshi M Thu, 02/05/2009 - 06:50
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Hi Remco,

I don't think that there hard numbers recommendation but it all depend on your design. You could create a /22 as you pointed out and avoid the need of routing various VLANs if they are all share the same functions.

As a point of reference, 1000 hosts will completely saturate a 10Mb network with nothing but control traffic.

Stick with /24 and route where necessary.

If you go above /24 implement private-vlans to control your broadcasts.

I have done work on a campus network that is a /20 and it sucks ... avoid if at all possible.


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