Figuring out the most efficient use of an ip range

Question

I am working with Packet Tracer atm and have 3 subnet plans :

assigned(management(104users)
staff(43 users)
admin(35 users)).

I have an ip address range of:38.191.0.0 and subnet mask of 255.255.255.0. I want to produce that subnet plan but with the most efficient use of the ip address range provided above.

Could anyone give me a brief idea of how to transform that range to the most efficient use of the IP addresses? I do have to implement VLAN's on each of the switches using router on stick methodology and the router interfaces will have ip's assigned from a range of 10.0.0.0 – 10.0.255.255. I'm a bit stuck at the moment.

The diagram looks as follows:

packet tracer

It's not clear what your trying to do: Are you subnetting the 38.191.0.0 network, or the 10.0.0.0 network? — Ron Trunk, Apr 29 '16 at 13:13
subnetting the 38.191.0.0, sorry for my english. the 10.0.0.0 range will be assigned to the router's serial interfaces — JGuerra, Apr 29 '16 at 13:15
The first step is to figure out the smallest subnet that will hold each of your user groups. So for example, what is the smallest subnet that will hold 104 users? — Ron Trunk, Apr 29 '16 at 13:24
104 users refers to the management users so I would suppose 38.191.0.0/25. 2^7=128. That will give me enough for the 104 users right? — JGuerra, Apr 29 '16 at 13:30
these are route-able IP addresses, are you assigning them to clients? — Sum1sAdmin, Apr 29 '16 at 13:31
subnet mask will then turn to 255.255.255.128 with 126 usable hosts — JGuerra, Apr 29 '16 at 13:32
Yes, they will be assigned to the number of users specified above — JGuerra, Apr 29 '16 at 13:36

score 0 · Accepted Answer · answered Apr 29 '16 at 13:39

You need, at least, 104 ips available on your subnet. What is most close to it is 128, from where you already have to remove 2 as they are going to be used for network address and broadcast address.

Having this in mind, and knowing that having a 24 bits prefix network address means having (255-2) available ips, you could only get one bit more for subnets.

The result would be:

Netmask: 255.255.255.128 = /25

Subnets:

1.
Network:    38.191.0.0/25         
HostMin:    38.191.0.1    
HostMax:    38.191.0.126  
Broadcast:  38.191.0.127  
Hosts:      126   

2.
 Network:   38.191.0.128/25         
 HostMin:   38.191.0.129    
 HostMax:   38.191.0.254    
 Broadcast: 38.191.0.255    
 Hosts:     126

Figuring out the most efficient use of an ip range

1 Answers1