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I quote the assignment:

"Consider an organization with 4000 hosts. Divide the hosts into two subnets containing 1000 and 3000 hosts. Choose network ID's and define the subnet masks so that the organization's requirements are fulfilled and the address space is as small as possible."

While I tried to figure this one out, I got stuck to the fact that you have to divide the hosts into two subnets with one 1000 and the second 3000. I felt like this wasn't possible and thought he might have meant like dividing into 2x /22 2046 hosts. So I wanted to know if this assignment is valid and if so how should I approach this problem?

SapphireBlazer01
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1 Answers1

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Your concern is valid and IMHO the question is either a trick question or badly worded - specifically the "into 2 subnets". By my reading to meet this clause you would need a fairly wasteful solution which requires a /19 to implement.

Try 1 * /20 (ie 4096 IP's) + 1 * /22 - If the subnets need to be carved out of a single existing block you would need a /19 - which you would divide into 1 /20 and 2 /22's - one of which would not be required.

If you can put aside the "2 subnets" requirement the answer would seem to be

1 * /21 + 2 * /22's - with 1 of the /22's assigned alongside the /21. This would put a little extra load on the router (or routing tables of the hosts), but would better meet the requirement of "the address space being as small as possible.

I wonder if the "correct" solution is to advise (1) above as the correct solution and point out that (2) above would be better if the requirement to divide into 2 subnets were waived.

davidgo
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