Question

1. Explain the following examples:

1. The decimal value of the binary number 11001101 and the binary value of the IPv4 address 126.128.192.223.
2. IPv6 addresses of 1001:890:600:d1:abcd:f010 and 2031:0:130F::9C0:876A:130B.
3. Subnet masks of 255.255.255.0 and 255.255.0.0 and 255.255.255.128 and 255.255.254.0.
4. Subnet portion of the IP address and what is the subnet mask for 12.1.0.0/16 and 12.1.0.0/24 and 12.1.0.0/20 and 12.1.0.0/28.
5. In all addresses, the first Class A byte is from 1 to 126, the first Class B byte is from 128 to 191, and the first Class C byte is from 192 to 223.

Answer 1

(a) Decimal value of 11001101 is 205.

Binary value of give IPv4 address is 0111 1110.1000 0000.1100 0000.1101 1111

Hope you know binary to decimal conversion and vice versa.

(b) What explanation you want about this. State clearly.

IPv6 addresses are 128 bit addresses. An IPv6 address has three parts.

First 48 bits from left is Global Routing prefix. This is assigned to an autonomous system.

Next 16 bits refers to the subnet ID.

Next 64 bits is interface ID.

48 bits + 16 bits + 64 bits = 128 bits.

An IPv6 address can be Global Unicast address or Unique local address or Link local address.

The three most significant bits of Global Routing Prefix is always set to 001.

1st IPv6 address is 1001:890:600:d1:abcd:f010 . 1001 in binary is 0001 0000 0000 0001. Hence, it is not a Global Unicast address. 2nd IPv6 address is 2031:0:130F::9C0:876A:130B. 2031 in binary is 0010 0000 0011 0001. We see that it is a Global Unicast address.

(c) Subnet mask of 255.255.255.0 means first three octets are part of network ID and last octet or last 8 bits form Host ID.

Subnet mask of 255.255.0.0 means first two octets are part of network ID and next two octets form Host ID.

Subnet mask of 255.255.255.128 means least significant 7 bits of last octet only is part of host ID, all other bits form network ID. CIDR is /25.

Subnet mask of 255.255.254.0 means 1 least significant bit of third octet and all 8 bits of fourth octet form Host ID, all other bits form Network ID. CIDR is /23.

(d) 12.1.0.0/16 - Subnet portion : 12.1 Host portion : 0.0

and 12.1.0.0/24 - Subnet portion : 12.1.0 Host portion: 0

and 12.1.0.0/20 - Subnet portion : 0000 1100.0000 0001. 0000 Host portion: 0000. 0000 0000 (in binary for better clarity)

and 12.1.0.0/28 - Subnet portion : 0000 1100.0000 0001.0000 0000.0000 Host portion; 0000 (in binary)

Last two has been represented in binary because the boundary falls inside the octet.

(e) In all addresses, the first Class A byte is from 1 to 126, the first Class B byte is from 128 to 191, and the first Class C byte is from 192 to 223.

I don't understand what explanation do you need for this. State clearly.

Class	1st Octet Decimal Range	1st Octet High Order Bits
A	1 – 126*	0
B	128 – 191	10
C	192 – 223	110