this is Exam question
can someone explain me what is correct answer for this
Network A requires at least a /25 to accommodate 120 hosts, which makes B the only option.
As far as link A is concerned, the answer could be D or E, but since D is contiguous with the 3 other links, I would say D is the logical one to pick.
From this question network A has 120 hosts. A subnet with /26 mask will support only 62 hosts. So network A needs a /25 mask which will support 126 hosts. So "B" is one of the answers. For link A the correct answer is "D" because the choice in E overlaps the network for Marketing in the drawing.
Link A just needs 2 IP's one for each router
Link A = 172.16.3.0/30
Usable 172.16.3.1 - 172.16.3.2
172.16.3.40/30 falls into the already used 172.16.3.32/27 network.
Network A needs 120 address, so the closest match here is a /25
Network A = 172.16.3.128/25
Usable 172.16.3.129 - 172.16.3.254
The other 2 /26 networks do not provide enough hosts as a /26 only gives 62 usable IP's.