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Home > Archive > CCNA > March 2001 > Subnet Q?
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| Hi,what is the answer to the following question:
You have the IP address 150.33.101.1 with a 12-bit (255.240.0.0) subnet mask. Which is a valid host ?
a 150.45.120.19
b 150.51.145.69
c 150.29.196.124
d 150.25.147.128
BTW,I don't know it,I got it form
http://leuthard.ch/exams.mv?getquizfile | |
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| I'm not an expert on subnetting but isn't that a class B address with a class A subnet mask? | |
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| Please check the question it pretty tough to have a question like that, is the subnet mask
255.255.240.0 or is the ip 150.33.101.1/12which is again different you say a 12 bit mask so I must assume 255.255.255.240 this is a 12 bit mask
according to cisco you cannot count the default which in the case of a class b network is 255.255.
so the a 12 bit mask would give you a mask of 255.255.255.240 with 4 bits for hosts you may want to recheck your question | |
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| hi ppp,
here are some example:
suppose u have an network address of 172.16.0.0
and subnet addess 0f 255.255.240.0 try to convert it to binary (just to see the borrowed bits) 111111111.11111111.11110000.00000000
since class B the default subnet mask is 255.255.0.0 but u borrowed 4 bits from the third octet which is the masked bits and the unmasked bits are those zeros left.
solution:
formula How to calculate the number of networks)
2^n-2= ans.
where n= is the masked bits
ans= total #of networks
so: 2^4-2=14
formulahow to calculate the number of hosts)
2^n-2= ans
where n= is the umasked bits
ans= total # of hosts
s0:2^12-2=4094
TO find out the subnets we subtract 256-240=16
* to solve the first three subnets
subnet 16 32 48
first address 172.16.1.1 172.16.32.1 172.16.48.1
last address 172.16.31.254 172.16.47.254
172.16.63.254
broadcast address 172.16.31.255 172.16.47.255
172.16.63.255
If you understand the concepts and how i do it,
then all subnetting questions u will be able to solve.
just try solve one ok.
regards,
pat | |
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| quote:
Originally posted by ppp
Hi,what is the answer to the following question:
You have the IP address 150.33.101.1 with a 12-bit (255.240.0.0) subnet mask. Which is a valid host ?
This is supernetting. You shouldn't see this on the CCNA test. BTW, the answer is A.
pat,
The number of subnets is 2^n. In some circumstances you won't use the first (all zeros) and the last (all ones) subnets, so you end up with 2^n - 2 usable subnets. The total number of subnets is still 2^n.
Cheers! | |
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| quote:
Originally posted by ppp
Hi,what is the answer to the following question:
You have the IP address 150.33.101.1 with a 12-bit (255.240.0.0) subnet mask. Which is a valid host ?
a 150.45.120.19
b 150.51.145.69
c 150.29.196.124
d 150.25.147.128
BTW,I don't know it,I got it form
http://leuthard.ch/exams.mv?getquizfile
150.x.x.x is a Class B address. The default subnet for a Class B address is 255.255.0.0 (11111111.11111111.00000000.00000000). Your question tells is we are using 12 bits for subnetting (this does not mean it's a /12 mask), giving us a subnet of 255.255.255.240 (or 11111111.11111111.11111111.11110000; or /28).
Network: 150.33.101.0
Valid Host Range: 150.33.101.1 - 150.33.101.14
Broadcast: 150.33.101.15
Unless I'm totally misunderstanding your question, none of the choices is correct. | |
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| hi dmaftei,
that's correct,
2^n is the right formula, which is the total subnets. i included
minus 2 just to make sure these are usable subnets.
smile always...
thanks,pat | |
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| quote:
Originally posted by patrick199621
smile always...
OK, here's the smile:  |
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