| 1: | What is subnetting? |
| A1: | Answer: Subnetting is a process by which a third level of addressing is created from IP's two-level address. The three address levels are network, subnetwork, and host address. A single network can be used to create several subnetworks, each of which can support numerous hosts. In very simple terms, subnetworks are just blocks of addresses reserved from within a network address. Each block of addresses can then function as a separate network-level address. |
| 2: | How many levels of addressing are possible in an IP address? |
| A2: | Answer: There are three levels of addressing possible within an IP address. The first two, network and host addresses, are a native component of an IP address. The third level is the subnet address. The subnet address is created by borrowing bits from the host address field. |
| 3: | What are some of the benefits of subnetting? |
| A3: | Answer: The three main benefits of subnetting are more efficient use of an IP network address, the ability to organize your resources within a network, and the ability to secure your resources by placing them into separate subnetworks. |
| 4: | What are two main drawbacks of subnetting? |
| A4: | Answer: The two main drawbacks of subnetting are that it introduces some waste of IP addresses and greatly complicates the chore of managing an IP address block. The waste of IP addresses in a subnetted environment is caused by the allocation of two IP addresses per subnet for subnet identification and broadcasting within that subnet. |
| 5: | Can you see a subnetwork address in a dotted-decimal IP address? |
| A5: | Answer: No. A subnetwork address consists of bits borrowed from the host address portion of an IP address. As such, it won't be readily discernable when you look at an IP address in its dotted-decimal form. You must first know the subnet mask and then convert the host's IP address to its binary form before you can see the subnetwork address. |
| 6: | What is a base address? |
| A6: | Answer: A base address is the first IP address in either a network address or a subnetwork address block. The base address typically serves as the address for that network or subnetwork. |
| 7: | What is an extended network prefix and what does it do? |
| A7: | Answer: The subnetwork address functions as an extension of the network address. The subnetwork and network addresses work together to form an extended network address. In fact, when viewed together, network and subnetwork addresses are known as an extended network prefix. An extended network prefix enables IP packets to be routed directly to your network but not to your specific workstation. |
| 8: | Name three types of masks encountered in an IP network. Explain what each does. |
| A8: | Answer: You will encounter three mask types in an IP network: decimal, network, and subnetwork masks. The decimal mask is better known as the dotted-decimal form of an IP address. It lets you avoid having to remember large strings of highly repetitive binary numbers, which is the raw form of an IP address. The network mask helps you see how large the network address block is by identifying just the bits used for network address identification. The subnetwork mask builds upon the network mask by adding the subnetwork address bits to the network address bits. The network and subnetwork masks can be used in either their decimal or binary forms. |