Explain the advantages and disadvantages of using a hierarchical model, such as the Cisco Three-Layer Hierarchical model, to build a network?
The hierarchical model focuses on the three functional areas of the network. The functional areas include: Core layer, Distribution layer and Access layer.
Advantages of using the hierarchical model
i. Scalability – This makes it possible to grow your network by diving it into functional areas
ii. Behavior prediction – It makes it possible for one to foresee what may happen to the network when new stresses are placed on it.
iii. Policy creation – When using the hierarchical model, it is easy to create policies and specify rules.
iv. High performance - When using the hierarchical model, it is possible to design high performance networks where only certain layers are subjected to congestion.
v. Efficient management – It is easy to organize your network when using the hierarchical model. This further makes it easy to identify causes of trouble and solve them in the shortest possible time.
vi. Cost – hierarchical networks require fewer administrator hours. It also ensures efficient use of hardware and other network resources thus saving on the overall cost.
Disadvantages of using the hierarchical model
i. Loss of IP hardware mobility
ii. Requires a lot more IP addresses to be used
Answer the following activities in a couple of brief sentences:
1. When working with IP addresses, which addresses can never be assigned to a host?
The first and last addresses in a subnet cannot be assigned to hosts as they are used as the network identifier and broadcast address respectively.
2. How can you tell if an IP address is a broadcast address if you write out the address in binary?
Perform a binary inversion of the CIDR or Netmask Address. The Bitwise OR Operator is then used to get the Broadcast address
3. What is the maximum number of bits that can be borrowed with a Class A address?
With class A you can borrow up to 22 bits.
4. What is the maximum number of bits that can be borrowed with a Class B address?
You can borrow up to 14 bits.
5. What is the purpose of a subnet mask?
It allows one to identify which part of the IP address is reserved for the network and that which part is available for host use. It does this by allowing the flow of network traffic between hosts to be segregated based on a network configuration. It can also improve network security and performance.
Lin C.C. & Chen S.H. (2004) The Hierarchical Network design problem for time-definite express common carriers. Elsevier Publishers.