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New Member

Broadcast domain size

Hello-  I have 2 4506 switches in our main office, both have 5 48 port blades.  They are configured with a data vlan and a voice vlan.  I can see on the fiber trunk port, network utilization isn't terribly high, but I wonder if the data vlan would benefit if I split it up in a couple of additional vlans.  Is there any best practice or recommendation for how many Windows hosts to place in a single vlan/broadcast domain on a 100 mbps network?

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VIP Super Bronze

Hi,There isn't a set rule or

Hi,

There isn't a set rule or standard on how many hosts should be in subnet/vlan, but if you use a /24 subnet per vlan, you should be fine.

HTH

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VIP Super Bronze

Hi,There isn't a set rule or

Hi,

There isn't a set rule or standard on how many hosts should be in subnet/vlan, but if you use a /24 subnet per vlan, you should be fine.

HTH

Cisco Employee

Hi jfinger,      What exactly

Hi jfinger,

 

     What exactly is your thought about creating a new VLAN, do you think your devices are suffering hard from bcasts? For bcasts to impact your network you would need to have a pretty big network and with services that need this type of packet running all the time, as Reza said, a /24 would be excellent for non-servers (For servers/DCs you would need a deeper understanding of what is running), even a /23 would not be a problem, but if you're thinking your workstations are not working pretty fast it may not be due to to bcasts, but more to how much traffic your devices are using, what is the model of this LCs? it will vary to how many ASICs you have on this card and how much traffic is actually passing through the switch. (Remember, if creating a new VLAN and allowing the same path, not load balancing this VLAN, you'll shorten the bcast domain size, but not necessarily increase end user available bdw). 

New Member

I was more or less just

I was more or less just seeing if there was a recommendation as to when additional VLANs would be necessary.  Network utilization looks low, but whenever I do a packet capture, I'm always amazed at how much broadcast traffic there is and if reducing broadcast domains would benefit overall performance.  Thanks.

Cisco Employee

Go for the simple /24 network

Go for the simple /24 network, if you need more than that, create a new VLAN.

Usually PCs use bcast for a lot of things, so if you have 100-200 devices on the same VLAN, I would not be amazed if it has tones of bcasts, it should not have much impact though.

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