I’m not sure if this is the right place to post this.
I’ve been following the CCENT official certification book(100-105) and came upon this question in the “do I know this already?” quiz. The books only covered /24 subnetting only so far.
Which of the following is a network broadcast address?
a. 10.1.255.255
b.192.168.255.1
c. 224.1.1.255
d. 172.30.255.255
As no subnetting notation has been included, I’ll stick with .255 ending as being broadcast.
a = seems correct.
b = incorrect. ends with .1
c = incorrect, it’s a class d multicast.
d = seems corrects too.
The answer says ONLY D is correct.
So why is A incorrect? My understanding:
10.1.255.0 as the network ID
10.1.255.1 to 10.1.255.254 as valid IP addresses.
10.1.255.255 as the broadcast
Class a = 8 Bits network ID. 24 Bits Host ID. (0 subnet bits as theirs only 1 whole subnet? is this correct?)
subnet mask = 255.0.0.0
Hi Bilal,
A) is indeed incorrect. Because you stated there is no subnetting in place.
10 is inside range from 1 to 127 making it class A. 10 is the major network network here.
Your explanation is correct. Default class A network is /8, making it 255.0.0.0 default subnet mask. If you want to get broadcast address simply turn all host bits to 1, thus you will end with 10.255.255.255 as broadcast address of major network 10. This is really huge broadcast address.
What is important for your question:
Class A has 255.0.0.0 default subnet mask
Class B has 255.255.0.0 default subnet mask
Class C has 255.255.255.0 default subnet mask
If you want to get broadcast address for these default major networks you have to turn octects with 0 to 255.
