Study question, please help!

[SnowNinja]

I'm working through some questions in my study guide for the CCNA and need some help with one of them (is it me, or are some CCNA questions deliberately confusing?)

Which of the following are true regarding a network with a subnet mask of 255.255.248.0. Choose three;

a. It corresponds to a Class A address with 13 bits borrowed.
b. It corresponds to a Class B address with 4 bits borrowed.
c. The network address of the last subnet will have 248 in the 3rd octet.
d. The first 21 bits make the host portion of the address.
e. This subnet mask allows for 16 total subnets to be created.
f. The subnetwork numbers will be in multiples of 8.

I want to post more questions this week, seems like the answers in my study guide are not logically consistent.

Thanks for any help you can give!

-SnowNinja

 

[Mshen]

c,d,f

any other thoughts?

 

[Cluebird]

a,c,f

d is not correct since the first 21 bits correspond to the network/subnetwork portion of the address. The host portion is the remaining 11 bits.

Although f is correct it is not worded clearly since the multiples of 8 occur in the third octet.

 

[SnowNinja]

How did you guys get answer "c"?

-SnowNinja

 

[GrnEyedLdy]

Available subnets using this mask

X.X.0.0 Subnet Zero 00000 000
X.X.8.0 00001 000
X.X.16.0 00010 000
X.X.24.0 00011 000
X.X.32.0 00100 000
X.X.40.0 00101 000
X.X.48.0 00110 000
.
.
.
X.X.200.0 11001 000
X.X.208.0 11010 000
X.X.216.0 11011 000
X.X.224.0 11100 000
X.X.232.0 11101 000
X.X.240.0 11110 000
X.X.248.0 All ones subnet 11111 000

Although Subnet Zero and the All Ones Subnet are not always used, they are valid subnets. So, C is True

c. The network address of the last subnet will have 248 in the 3rd octet.

 

[Mshen]

aha,

my mistake..

d is wrong..

 

[jabw]

The dirty part of these answers is, to my opinion, in answer c: ...of the last subnet...
As is shown in the answer by GrnEyedLdy.