Networking - Subnetting - Discussion
Discussion Forum : Subnetting - Subnetting (Q.No. 7)
7.
If an Ethernet port on a router were assigned an IP address of 172.16.112.1/25, what would be the valid subnet address of this host?
Answer: Option
Explanation:
A /25 mask is 255.255.255.128. Used with a Class B network, the third and fourth octets are used for subnetting with a total of 9 subnet bits, 8 bits in the third octet and 1 bit in the fourth octet. Since there is only 1 bit in the fourth octet, the bit is either off or on-which is a value of 0 or 128. The host in the question is in the 0 subnet, which has a broadcast address of 127 since 128 is the next subnet.
Discussion:
14 comments Page 1 of 2.
Stranger said:
10 years ago
I don't understand this please help.
Manu Ratheesh said:
10 years ago
Given IP is 172.16.112.1/25 => NID is 25 bits.
We know that subnet mask is obtained by replacing all NID bits with 1 and HID bits with 0.
So SM is 255.255.255.10000000 (First 25 bits is NID and the last 7 bit is HID).
i.e, SM is 255.255.255.128.
Now the subnet address is obtained by (SM) AND (IP).
=> (255.255.255.128) AND (172.16.112.1) = 172.16.112.0.
Option (A).
We know that subnet mask is obtained by replacing all NID bits with 1 and HID bits with 0.
So SM is 255.255.255.10000000 (First 25 bits is NID and the last 7 bit is HID).
i.e, SM is 255.255.255.128.
Now the subnet address is obtained by (SM) AND (IP).
=> (255.255.255.128) AND (172.16.112.1) = 172.16.112.0.
Option (A).
Mehedi hasan dipu said:
10 years ago
I think this answer is incorrect what will be the right answer. If this answer is correct so then please describe the correct answer.
Simham said:
9 years ago
Why are taking Class B? This is a classless domain. Can any one please tell me.
(1)
Lucas Mathew said:
9 years ago
Why use class C subnet mask if the IP is in class B?
(1)
Gurpreet singh said:
9 years ago
Sometimes it happens our IP series belongs to class b IP but subnet mask of class. So when ever its happen you have to see IP address behave on that you can understand series, in this question. IP address starts with 172 that mean class b IP.
Jimbo jones said:
9 years ago
I think the answer is 172.16.0.0 network. It's still a class b network so you can only touch the 3rd octet.
Mani said:
8 years ago
172.16.112.1/25 question simply 24 bit octal +1 another eight 0, so ip address 172.16.112.0 mention 1;.
(1)
Amala said:
8 years ago
Then what's the no of networks and host per network?
Naomi Nash said:
6 years ago
Then what's the no of networks and host per network?
Being 1 bit in the last bit is affected, the number of networks (which is the same as subnets) is;
Subnet= 2^n.
=2^1,
=2.
A number of Hosts= 2^k-2.
Number of Host bits= 32-25=7 bits,
=2^7-2,
=128-2,
=126 Hosts per subnet.
Being 1 bit in the last bit is affected, the number of networks (which is the same as subnets) is;
Subnet= 2^n.
=2^1,
=2.
A number of Hosts= 2^k-2.
Number of Host bits= 32-25=7 bits,
=2^7-2,
=128-2,
=126 Hosts per subnet.
(2)
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