MadeEasy Test Series: Computer Networks - Subnetting

Question

For a class C network if IP address of a computer is 200.99.39.112 and subnet mask is 255.255.255.224 the first host of first subnet (represent last octet) is ________.

my question is that whether to take 1st host as '000' or '001'.?

according to me 1st host should be 000,so accordingly answer will be 200.99.39.00000001..ANSWER=1

but they had taken 200.99.39.00100001..ANSWER=33

Comments

yes your ans is right first host of first subnet is 200.99.39.1 so ans=1

Answer 1

All 0s in Host id part represent 1st address of network (Subnet) and all 1s in Host id id part represent Directed Broadcast address of that Network (Subnet)..

In case of Subnet u r allowed to take all 0s as well as all 1s as Subnet bit bt Host should not be all 0s or All 1s..

Comments

yeah thats  why i have taken it as "00000001"...so answer is 1?

---

yes !!!

---

it was 3rd mistake contiguously from MADE EASY :D!

---

the ans can not be 33 no doubt but ans can not be 1 too.. why we are not considering subnet id?.. first we have to do bitwise and between the ip and subnet mask to know the subnet id where the ip belongs and it comes out to be 01100000 so 1st host id will be 01100001. i think this should be the right way???

Answer 2

For any range of ip addresses ,,,the first and the last ip address cannot be used for the hosts. If someone has to send a directed broadcast to ur network he will use the first ip address for that. hence configurable host ip addresses will start from 001

Answer 3

As it's mentioned it's Class C and Subnet mask is given we can get the N/w 

its {200.99.39._ _ _ } {_ _ _ _ _}

     <--------N/w------> <---Hid--->

so it is first host of first subnet ... that is {200.99.39. 001} {00001}

which is 200.99.39.33 

Comments

you are wrong. the subnet id is 011. not 001. your approach is right but ans can not be 33.

we can find subnet id by performing bitwise and with subnet mask and the given ip. and it comes out to be 01110000 bitwise and 11100000 = 01100000 (basically 112 bitwiseAND 224)

so subnet id comes out to be 011 so 1st host id is 01100001