A user is unable to connect to a server in another building. A technician is troubleshooting the issue and determines the following:
1) Client PC 1 has an IP address if 192.168.10.25/25
2) PC 1 can successfully ping its gateway of 192.168.10.1/25 which is an interface of router A
3) Server A is named ‘BLDGBFILESRVR01’ and has an IP address of 192.168.10.145/25
4) PC 2 with an IP address of 192.168.10.200/25 can successfully ping server A
However, when PC 1 pings server A, it receives a destination host unreachable responds. Which of the following is the MOST likely cause?
A.
Link from touter A to PC 1 are on different subnets
B.
Link from router A to server A is down
C.
Link from PC 1 to router A has duplex issues
D.
Link from server A top PC 2 is down
Because we have borrowed 1 bit from the standard netmask (it’s /25 instead of /24) this means we have taken the first bit away from the client machine. For example, on a /24 network it would be
(H=host, C=client)
HHHHHHHH HHHHHHHH HHHHHHHH CCCCCCCC (so we have the full amount of bits available to the client)
In our example it is /25 address so it’s
HHHHHHHH HHHHHHHH HHHHHHHH HCCCCCCC
This means we have the extra bit taken from the end (taken away from clients and given to the host range instead), this is the 128 bit, this means we only have 127 usable addresses left (255 minus 128).
The IP of the computer is
192.168.10.25/25
The maximum in this /25 class of network is 192.168.10.127/25 (although that would be the broadcast address so 126 really we can use for our clients.
The Server IP is 192.168.10.200/25 (we can’t get to .200 (even starting at .25) with only 7 bits, binary maths time to check… 1+2+4+8+16+32+64 = 127)
Therefore the answer is correct and it’s on a different subnet.
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