considering the following scenario:
"You are the administrator of your company's network, which uses TCP/IP as its only protocol. The network uses the private address space of 172.16.0.0/16.
Your company projects rapid growth during the next three years. To reduce the risk of network saturation, you decide to subnet the network. You will eventually need to accommodate a maximum of 17 subnets. Each subnet will include a maximum of 1,200 hosts. Which subnet mask should you configure to meet both your current needs and your projected needs?"
my questions are:
1) doesn't "172.16.0.0/16" mean IP address of 172.16.0.0 with a subnet mask of 255.255.0.0? why do we have to configure another subnet mask?
2) 17 subnets with each subnet including 1200 hosts will be 20400 hosts. so 2^15 is 32768 which is larger than 20400. so i thought i should leave 15 bits for these hosts and therefore 17 bits is left(32-15=17). so in binary, that would be 11111111.11111111.10000000.0000000 which in decimal would be 255.255.128.0. unfortunately my answer was wrong. Could anyone show me how to do the calculation correctly?
Thanks a lot in advance,