ISRO2008-3

Question

The subnet mask $255.255.255.192$

• A. extends the network portion to $16$ bits
• B. extends the network portion to $26$ bits
• C. extends the network portion to $36$ bits
• D. has no effect on the network portion of an IP address

Comments

@ ARJUN SIR KINDLY CHECK THE ANS...

Answer 1

Answer :Extend the network portion to 26 bit

The sub-net of Class C which has 3 networks and 1 host.
3-Networks each network of 8-bits i.e 8+8+8=24
Default sub-net mask for Class C is 255.255.255.0/24
128 64 32 16 8 4 2 1
1 1 0 0 0 0 0 0
128+64=192
192 is written as 11000000 which has 2 sub-nets and remaining all hosts.
255.255.255.0/24+2 = 255.255.255.192/26

Comments

How you know that it is class B , it can be class C or A as well

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Every Class has its IP range. Class C has from 192.0.0.0 to 223.255.255.255.

From wikipedia

 

Class	Start address	End address	Default subnet mask in dot-decimal notation
Class A	0.0.0.0	127.255.255.255[a]	255.0.0.0
Class B	128.0.0.0	191.255.255.255	255.255.0.0
Class C	192.0.0.0	223.255.255.255	255.255.255.0
Class D (multicast)	224.0.0.0	239.255.255.255	not defined
Class E (reserved)	240.0.0.0	255.255.255.255[b]	not defined

Answer 2

ANS IS D.

BECAUSE WE WILL NOT ALLOW  OR DESIGN IP AS PER SUBNET MASK

THE IP ADDRESS CAN BE ANYTHING IRRESPECTIVE TO THE SUBNET MASK

Comments

@arjun sir check this answer

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in the continuous mask we look for the number of 1's followed by zero so

NID+SID =24+2 =26  //which extend the network portions

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Does subnet portion and network portion can be considered as same?