Link to home
Start Free TrialLog in
Avatar of jskfan
jskfanFlag for Cyprus

asked on

Recommended size of Subnet

I wonder what's the recommended size of each subnet. for instance how many hosts should be in each subnets, considering mapping Vlan to subnet.
Example:
let's say I have this network 172.16.0.0/16 that I will subnet and make it 172.16.0.0/24
This will give me 256 Subnets of 254 hosts each, and each Subnet will have it is own Broadcast address : example:
Network:   172.16.0.0/24          
Broadcast: 172.16.0.255          
HostMin:   172.16.0.1            
HostMax:   172.16.0.254          
Hosts/Net: 254                    


Network:   172.16.1.0/24          
Broadcast: 172.16.1.255          
HostMin:   172.16.1.1            
HostMax:   172.16.1.254          
Hosts/Net: 254

As know Best practice is to map each subnet to a specific Vlan. however I am not sure if 254 hosts in one  Vlan does not impact performance.

OR do I need to subnet it further:  to /25 or /26 in order to have smaller subnets ?

Thanks
ASKER CERTIFIED SOLUTION
Avatar of Don Johnston
Don Johnston
Flag of United States of America image

Link to home
membership
This solution is only available to members.
To access this solution, you must be a member of Experts Exchange.
Start Free Trial
SOLUTION
Link to home
membership
This solution is only available to members.
To access this solution, you must be a member of Experts Exchange.
Start Free Trial
I agree with Don Johnson.  One size does not fit all.  That answers your question pretty well.
It's important to first define what your problem is.
Avatar of jskfan

ASKER

172.16.0.0/25 will give 512 Subnets with 126 Hosts each.

So if a VLAN has 126 hosts , will that be too much with regards to performance ?
SOLUTION
Link to home
membership
This solution is only available to members.
To access this solution, you must be a member of Experts Exchange.
Start Free Trial
You should be fine with /25.
2 subnets with 126 hosts each constitute 2 separate broadcast domains as they have a routed interface separating them. That's one of the main purpose of subnetting, to contain broadcast domains in small chunks.
It's like dividing a class of 510 grade 2 students into 2 classes. Imagine 126 students shouting (broadcasting) messages to everyone compared to 510 students shouting messages. There is more discombobulation in the class of 510 than 126.
You should however implement QoS on your core switch. Auto QoS should suffice
Avatar of jskfan

ASKER

Thank you