Subnetting

Which command will assign the last usable IP address from the 192.168.32.128/28 subnetwork to
a router interface?
A. Router(config-if)# ip address 192.168.32.142 255.255.255.240
B. Router(config-if)# ip address 192.168.32.143 255.255.255.240
C. Router(config-if)# ip address 192.168.32.158 255.255.255.240
D. Router(config-if)# ip address 192.168.32.142 255.255.255.248
E. Router(config-if)# ip address 192.168.32.144 255.255.255.224
F. Router(config-if)# ip address 192.168.32.158 255.255.255.224

So
/28=255.255.255.240 (11111111.11111111.11111111.1111.0000)
subnet: 2^4 = 16
host-per subnet: (2^4)-2=14
valid subnet: 256-240=16 (increment number)

0,16,32,64,80,96,112,128,144,160,176,192,208,224,240,256

broadcast address: subnet #9 : 192.168.32.143
valid host: 192.168.32.129 - 192.168.32.142

broadcast address: subnet #10: 192.168.159
valid host: 192.168.32.145 - 192.168.32.158

I can understand: D,E,F are incorrect.

B is the broadcast address.

Why the answer is A? not C? Please explain.

Thank you,

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Comments

yengiang

Which IP addresses are valid for hosts belonging to the 10.1.160.0/20 subnet? (Choose three.)

A. 10.1.168.0
B. 10.1.176.1
C. 10.1.174.255
D. 10.1.160.255
E. 10.1.160.0
F. 10.1.175.255

/20= 240 (11110000)
increment: 16 - (0,16,32...160,176...)

It rules out B(??) and E (160.0-network ID). What are the correct 3 out of A,C,D and F? Thanks

bbarrick

B. is in the 176 subnet.
E. Is a Subnet ID
F. Is a Broadcast Address

Leaving you A, C and D.

FrankGuthrie

The 10.1.160.0/20 subnet goes from 10.1.160.1 to 10.1.175.254.

A 20 bit subnet gives you a subnetmask of 255.255.240.0. This means you get blocks of 16 in the 3rd segment:

10.1.160.0 - 10.1.175.254
10.1.176.0 - 10.1.191.254
10.1.192.0 - 10.1.207.254
10.1.208.0 - 10.1.223.254
10.1.224.0 - 10.1.239.254
etc......

Notice the 3rd subnet increasing with 16. That is the block reserved by using a subnetmask of /20. Remember 20 network bits are used to determine the network and 12 bits are left for the host portion.

11111111.11111111.11110000.00000000
255 .255 . 240 .0

With that in mind, the only answers are A, C and D. Why you only have those left are explained by bbarrick

TechGuru80

It's not an increment question.

What Is Administrative Distance? - Cisco Systems

bbarrick

None of them give the proper command for a non-default AD as far as I can tell though. The answer he says the book provides doesn't really make much sense.

bbarrick

TechGuru80 wrote: »

It's not an increment question.

What Is Administrative Distance? - Cisco Systems

Not also, there was another question after the AD question.

yengiang

This forum is awesome. Thanks for helping me with the "subneting part".

bbarrick

It's against the rules to post actual test questions. Might want to edit that post if you can.

TechGuru80

bbarrick wrote: »

Not also, there was another question after the AD question.

Noticed that when I hit reply from the first page.

yengiang

bbarrick wrote: »

Not also, there was another question after the AD question.

Do you mean I can't post 2 questions?

yengiang

bbarrick wrote: »

It's against the rules to post actual test questions. Might want to edit that post if you can.

Please show me the rules link. Thanks.

bbarrick

yengiang wrote: »

Please show me the rules link. Thanks.

If you take a Cisco test you agree to those rules. You could lose your cert over it I believe.

You can post as many questions as you like in this thread as far as I am concerned. I was just letting the other poster know that another question had been asked.

yengiang

bbarrick wrote: »

If you take a Cisco test you agree to those rules. You could lose your cert over it I believe.

You can post as many questions as you like in this thread as far as I am concerned. I was just letting the other poster know that another question had been asked.

I'm here to learn and share...I probably have to take more test just to get familiar with those "rules". It's been 13 years since I took my last cert...:)

bbarrick

yengiang wrote: »

I'm here to learn and share...I probably have to take more test just to get familiar with those "rules". It's been 13 years since I took my last cert...:)

That's probably the most important thing you should remember with Cisco, probably other cert tests as well. There are sites called brain **** that have actual test questions. Utilization of these sites can cost you your cert, posting actual cert questions can as well. Hang around here for awhile and you will see it ad nauseam.

yengiang

bbarrick wrote: »

That's probably the most important thing you should remember with Cisco, probably other cert tests as well. There are sites called brain **** that have actual test questions. Utilization of these sites can cost you your cert, posting actual cert questions can as well. Hang around here for awhile and you will see it ad nauseam.

Well...that's inevitable. I'm not really concerned. My main goal is learning subneting, therefore, I'll keep posting question about subneting regardless.