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- Subject
- Posted on
- valid subnet numbers
- 02-28-2007
- barret bonden
February 28, 2007, 8:34 pm
The Cisco ccna book has a test question :
what are the valid subnet numbers for
180.1.0.0 mask 255.255.248.0
Now...
when I use the formula in my study guide AND when I use a subnet calc
program on the web I get the same
wrong answer, that is valid numbers in this net are from 180.1.0.1 -
180.1.7.254
The ccna guide tells me the right answer is that subnet 0 is 180.1.0.0 and
then 180.1.8.0 ,180.1.16.0 etc up to 180.1.240.0 (last valid subnet ) ...
180.1.248.0 (broadcast)
What am i doing wrong ? Any help ?
what are the valid subnet numbers for
180.1.0.0 mask 255.255.248.0
Now...
when I use the formula in my study guide AND when I use a subnet calc
program on the web I get the same
wrong answer, that is valid numbers in this net are from 180.1.0.1 -
180.1.7.254
The ccna guide tells me the right answer is that subnet 0 is 180.1.0.0 and
then 180.1.8.0 ,180.1.16.0 etc up to 180.1.240.0 (last valid subnet ) ...
180.1.248.0 (broadcast)
What am i doing wrong ? Any help ?
Re: valid subnet numbers
I owuld say that
The ccna guide tells me the right answer is that subnet 0 is 180.1.0.0
and
is the right answer-I cant see how 180.1.7.254 could be the last
available host
The mask is telling you that the subnets are in sets of 8-not that the
range only allows you to go to 180.1.7.254-that is signifying one
possible subnet-the first.
I would be grateful for some one to clarify please.
Re: valid subnet numbers
You have to read question very carefully. If it asks for subnets (network
numbers), then their answer is correct. Networks are: 180.1.0.0, 180.1.8.0,
180.1.16.0, etc. If they ask about HOSTS, then your calculations are right.
Just remember, what components do you have in the subnet:
1. Network Address: 180.1.0.0
2. Valid Hosts Addresses: 180.1.0.1 - 180.1.7.254
3. Network Broadcast Address: 180.1.7.255
Then next SUBNET starts...
Good luck,
Mike
------
Headset Adapters for Cisco IP Phones
www.ciscoheadsetadapter.com
numbers), then their answer is correct. Networks are: 180.1.0.0, 180.1.8.0,
180.1.16.0, etc. If they ask about HOSTS, then your calculations are right.
Just remember, what components do you have in the subnet:
1. Network Address: 180.1.0.0
2. Valid Hosts Addresses: 180.1.0.1 - 180.1.7.254
3. Network Broadcast Address: 180.1.7.255
Then next SUBNET starts...
Good luck,
Mike
------
Headset Adapters for Cisco IP Phones
www.ciscoheadsetadapter.com
Re: valid subnet numbers
Like everyone else says, the question is asking only for subnet (network)
numbers, not valid host addresses in a subnet.
Shortcut I use is take the interesting octet (3rd) of (the .248) in the mask
and subtract from 256. 256-248=8 so blocksize of subnets is 8 (they
increment by 8 in the 3rd octet).
Theoretical valid subnets are 180.1.0.0; 180.1.8.0; 180.1.16.0; 180.1.24.0;
180.1.32.0... and on up to 180.1.248.0. I believe for the CCNA you can't
use the first or last subnets so practical subnets would be 180.1.8.0;
180.1.16.0; 180.24.0... 180.1.240.0.
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