You are the network administrator for Woodgrove Bank. The company has 20,000 users in 20 physical locations worldwide. The company is expecting to grow by 50 percent in the next five years. The company recently became a subsidiary of Humongous Insurance. Humongous Insurance has five other subsidiaries.
Humongous Insurance has 100,000 users in 100 physical locations worldwide. Humongous Insurance uses the 10.0.0.0/8 network and requires that all subsidiaries integrate into this network. The network design team at Woodgrove Bank provides you with a network design for integrating into the Humongous Insurance network.
The design specifies that Woodgrove Bank will use a single block of IP network numbers to assign IP addresses to its network. You need to plan the IP address space to meet the design specification. You need to request a block of IP addresses from Humongous Insurance that will accommodate all Woodgrove Bank users.
To reduce the difficulty of obtaining the addresses and to conserve the Humongous Insurance address space, you want to request the smallest block of IP addresses that meets the design specification.
What should you do?
A.
Request a 10.0.0.0 block of IP addresses with a 32-bit subnet mask from Humongous Insurance.
B.
Request a 10.0.0.0 block of IP addresses with a 16-bit subnet mask from Humongous Insurance.
C.
Request a 10.0.0.0 block of IP addresses with an 8-bit subnet mask from Humongous Insurance.
D.
Request a 10.0.0.0 block of IP addresses with a 24-bit subnet mask from Humongous Insurance.
Explanation:
We have 20,000 users in 20 locations which would give us an average of 1,000 users per location. We need to make provision for a 50% growth so that makes in 1,500 users per location. We need to integrate this network with the Humongous Insurance network which uses the 10.0.0.0 network.
This means we must use the 10.0.0.0 network.Subnetting is the process of shifting the subnet mask so as to increase or decrease the number of bits reserved for the network addresses. In this instance we are using a Class A address, so the number of clients is important. A simple formula of 2(32-n)-2, where n is the number of bits in the subnet mask, can be used to calculate the number of hosts a network will support.
The best subnet mask would be a 21-bit mask which would give us 2,097,150 networks with 2046 clients per network. However, a 21-bit subnet mask is not offered as an option so we must use the next best subnet mask which would be 16. This would give us 65,534 networks with 65,534 clients per network.
Reference:
Thomas Shinder and Debra Littlejohn Shinder, Planning and Maintaining a Windows Server 2003 Network Infrastructur* Exam 70-293, Syngress Publishing, Rockland, MA, 2004, pp. 173-180.