Assume a host computer has the following configuration: IP Address: 139.100.110.

Question

Assume a host computer has the following configuration:

IP Address:

139.100.110.176

Subnet Mask:

255.255.0.0

Default Gateway:

139.100.1.1

a.What is the Class of this network?

b.Has this network been sub-netted? How do you know?

c.How many possible hosts would there be on the above network if all usable addresses were assigned?

d.How would this IP address be expressed using CIDR notation?

e.What is the range of the block of addresses this Host belongs to using CIDR notation?

IP Address:

139.100.110.176

Subnet Mask:

255.255.0.0

Default Gateway:

139.100.1.1

Explanation / Answer

ANS (a) : The Class of this Network is 'B'.

Note : Range of Class B =>128.0.0.0 - 191.255.255.255.255

ANS (b):

Subnetting an IP network is to separate a big network into smaller multiple networks for reorganization and security purposes. All nodes (hosts) in a subnetwork see all packets transmitted by any node in a network. Performance of a network is adversely affected under heavy traffic load due to collisions and retransmissions.

Applying a subnet mask to an IP address separates network address from host address. The network bits are represented by the 1's in the mask, and the host bits are represented by 0's. Performing a bitwise logical AND operation on the IP address with the subnet mask produces the network address.

For example, applying the Class B subnet mask (255.255.0.0) to our IP address 139.100.110.176 produces the following network address:

IP: 1000 1011 . 0110 0100 . 0110 1110 . 1011 0000 (139.100.110.176)

Mask: 1111 1111 . 1111 1111 . 1111 1111 . 0000 0000 (255.255.255.000)

      ----------------------------------------------------------------------------------------------------

1000 1011 . 0110 0100 . 0110 1110 . 0000 0000 (139.100.110.000)

Subnetting Network

Here is another scenario where subnetting is needed. Pretend that a web host with a Class B network needs to divide the network so that parts of the network can be leased to its customers. Let's assume that a host has a network address of 139.100.110.000 (as shown in the example above). Let's say that we're going to divide the network into 2 and dedicate the first half to itself, and the other half to its customers.

ANS (c): No of Possible Host : 65,534 BCZ Subnet Mask:255.255.0.0

ANS (d):

CIDR - Classless Inter Domain Routing

Classless InterDomain Routing (CIDR) was invented to keep the Internet from running out of IP Addresses. The IPv4, a 32-bit, addresses have a limit of 4,294,967,296 (232) unique IP addresses. The classful address scheme (Class A, B and C) of allocating IP addresses in 8-bit increments can be very wasteful. With classful addressing scheme, a minimum number of IP addresses allocated to an organization is 256 (Class C). Giving 256 IP addresses to an organization only requiring 15 IP addresses is wasteful.

Also, an organization requiring more than 256 IP addresses (let's say 1,000 IP addresses) is assigned a Class B, which allocates 65,536 IP addresses. Similarly, an organization requiring more than 65,636 (65,634 usable IPs) is assigned a Class A network, which allocates 16,777,216 (16.7 Million) IP addresses. This type of address allocation is very wasteful.

With CIDR, a network of IP addresses is allocated in 1-bit increments as opposed to 8-bits in classful network. The use of a CIDR notated address can easily represent classful addresses (Class A = /8, Class B = /16, and Class C = /24). The number next to the slash (i.e. /8) represents the number of bits assigned to the network address. The example shown above can be illustrated with CIDR as follows:

139.100.110.176, with subnet mask of 255.255.0.0 is written as 139.100.110.176/17

ANS: (E) Sorry

Related Questions

Navigate

• Browse (All)
• Browse A
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.