How to design a subnet?
Design an appropriate subnet mask taking into account the specified growth. Where applicable, your solution must be biased towards growth in LANs rather than hosts.
Host = 60
LAN = 90
Update:LAN will grow by 3% each year over 4 years
3% = 0.03 +1 = 1.03.
90 * 1.03 = 93 (per year)
= 101.29 = 101 LANS over 4 years
Hosts will grow by 5% each year over 4 years
5% = 0.05 +1 = 1.05.
60 * 1.05 = 63 (per year)
=72.93 = 73 Hosts over 4 years
More Questions From This User See All
Answers & Comments
Verified answer
Where is your attempt to answer this question?
The simplest answer for IPv4 addressing is 255.255.255.192.
When you update your question with your calculations and assumptions, I will add the details of how this is worked out.
Update:
If the hosts are growing at 5%/year over 4 years, and assuming that you mean 5% on each LAN, rather 5% overall, then the figures for each year over a 4 year period will be:
60 then 63 then 67 then 71 then 75 rounding up eat the end of each year.
Now a subnet will have three extra addresses for the subnet ID, the broadcast address and the address of gateway (router) to allow connection to the other LANs.
75 + 3 = 78. Now round this up to the next power of 2 = 128 or 2^7.
2^7 (2 to the power 7) means that there will be 7 bits in the address to define the specific host and 32-7 bits to define the subnet (LAN). This means the mask will have:
32 - 7 = 25 one bits and 7 zero bits
11111111 11111111 11111111 10000000
or
255.255.255.128
The number of LANs does not affect the subnet mask at all.
However, there is an alternative calculation:
You start off with 60 hosts on 90 LANs = 5400 hosts.
The hosts grow by 5%/year:
5400 then 5670 then 5954 then 6252 then 6565 rounding up at the end of each year
But the number of LANs is growing by 3%/year:
90 then 93 then 96 then 99 then 102
This gives 6565 / 102 = 65 hosts per LAN after 4 years.
Adding the extra 3 addresses (68) and rounding up to the power of 2 (128) means we end up with the same subnet mask.
In the first calculation there will be 75 hosts per LAN after 4 years, but in the second calculation there are only 65 hosts per LAN. The question does not make it clear whether the 5%/year increase in hosts is across the entire network or across each individual LAN. It makes no difference to the subnet mask as both will give enough hosts on each LAN to require the same mask.
You will get the same results for the mask if you round up only after the fourth years and not after each year, but I have not included these alternative calculations.
I hope this helps.