Hello! Please could someone help me on this one. The question can be found on 13-8 of ms press 70-291 (1st edition).
Question:
Your organisation has leased the class c network 199.205.14.0/24. You are subnetting this network using VLSM. Your routers support the zero subnet and the longest match algorithm. You ask one of your support staff to design a subnetting structure but when she submits this you suspect that some of the network/subnet mask allocations are invalid. Which of the following are not valid networks?
A) 199.205.15.64/25
199.205.15.192/26
C) 199.205.15.130/26
D) 199.205.15.96/26
E) 199.205.15.8/27
F) 199.205.15.40/28
I chose A, C, D, E and F. And MS press says only A, C, E are correct. After reviewing their explanation as to why D and F were not correct, it states:
D) Mask = 255.255.255.224
Increment = 256-224 = 32
F) Mask = 255.255.255.248
Increment = 256-248 = 8
This is what stumped me, why does it state the mask is .224 when /26 = 192? And with F why does it state .248 when /28 = 240.
Thanks in advance!
