A collegue at work came to me with this question any ideas?

Your network has 1900 hosts and requires internet connectivity, your network is not routed, xcept to the internet.
You have been assigned the follwoing 8 ip address
192.243.32.0/24
192.243.33.0/24
192.243.34.0/24
192.243.35.0/24
192.243.36.0/24
192.243.37.0/24
192.243.38.0/24
192.243.39.0/24

You want to minimise the complexity of your routing table which sunbnet mask should you use?

A 255.255.252.0
B 255.255.248.0
C 255.255.255.248
D 255.255.240.0

The answer he's got is B but I think it might be D. A subnet mask of 240 gives 14 (valid) subnets. Something like:-

192.243.16.0 to 192.243.31.254
192.243.32.0 to 192.243.47.254
192.243.48.0 to 192.243.61.254
192.243.62.0 to 192.243.77.254
192.243.78.0 to 192.243.93.254
192.243.94.0 to 192.243.109.254
192.243.110.0 to 192.243.125.254
192.243.126.0 to 192.243.141.254
192.243.142.0 to 192.243.157.254
192.243.158.0 to 192.243.173.254
192.243.174.0 to 192.243.189.254
192.243.190.0 to 192.243.205.254
192.243.206.0 to 192.243.221.254
192.243.222.0 to 192.243.238.254


A subnet mask of 248 gives 30 which I guess would work ok too but with more subnets and less hosts which for some reason I think is a bad thing, Wouldnt it give more entries in the routing table?


Am I right or sheeeite?
My TCP/IP is a bit weak.

If your viewing this and understand IP addressing (I dont!) then dont be lazy just reply!!

Cheers
DD

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I thought I understood subnetting, until I saw that question.
I am confused with the fact that the address is 192 which is class C which would have an a subnet mask of 255.255.255.? I thought any borrowing of bits would have to happen in the last octet?
Any explanations?

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I've seen this question a few times on the various exam tools out there.

Your network has 1,900 hosts, and requires Internet connectivity. Your network is not routed, except for the connection to the Internet. You have been assigned the following eight network addresses from your ISP:

192.24.32.0/24
192.24.33.0/24
192.24.34.0/24
192.30.35.0/24
192.30.36.0/24
192.30.37.0/24
192.30.38.0/24
192.30.39.0/24

Your goal is to minimize the complexity of the routing tables, while maintaining Internet connectivity for all hosts. What subnet mask should you use?
255.255.248.0

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If you are using several subnets, you would need a router within your network to communicate between them. Not just to get to the Internet. So for 1900 users, you need to have a Host portion of the IP address of at least 11 bits (2^11=2048). To do this with Class C networks you would need to SUPERNET.

You will want to double check this answer as it is just my thoughts as someone just getting started studying for this exam.

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