IP Networking: Midterm Study Guide
Subnetting—
Determine the classes – Classful vs Classless
Class A: The first bit in the first octet must remain a 0. The remaining seven bits can be a 1, giving a maximum total of 127. The first octet, however, cannot be 0 (local identification, or “this network”) or 127 (loopback). Class A first octet range is 0 through 127, although the valid range is 1 through 126.
Class B: The first bit in the first octet becomes a 1. The second bit, however, must remain a 0. The remaining six bits can be a 1, giving a maximum total of 191. Class B first octet range is 128 through 191.
Class C: The first and second bits in the first octet become 1s. The third bit must remain a 0. The remaining five bits can be a 1, giving a maximum total of 223. Class C first octet range is 192 through 223.
How many usable hosts?
To determine the number of usable hosts, use the formula (i.e.).
Subnet Mask – CIDR
The subnet determines how many subnets a network will have and, consequently, how many hosts each subnet will have. The mask, when in binary form, will display the bits in 1s and 0s respectively. Those bits that are 1s are considered network/subnet bits, and those bits that are 0s are considered host bits.
When determining how many subnets will be created from a specific mask, consideration of the IP address’s class must be taken. Class A addresses have a default mask of 255.0.0.0; therefore, any 1s after the first octet will be considered subnet bits.
The total number of network and subnet bits equal an address’s prefix. If a Class A address of 10.10.33.46 has a mask of 255.255.224.0, then all of the 1s in the binary form of that mask, which totals 19, would be the prefix. In CIDR notation, the address would be seen as 10.10.33.46/19.
Dotted decimals
IP Addresses are, for human intellect, noted in dotted decimal notation. Computers and other devices see IP addresses in binary: that is, a series of 0s and 1s. However, for human eyes and thinking, it is translated into four octets of
Determine the classes – Classful vs Classless
Class A: The first bit in the first octet must remain a 0. The remaining seven bits can be a 1, giving a maximum total of 127. The first octet, however, cannot be 0 (local identification, or “this network”) or 127 (loopback). Class A first octet range is 0 through 127, although the valid range is 1 through 126.
Class B: The first bit in the first octet becomes a 1. The second bit, however, must remain a 0. The remaining six bits can be a 1, giving a maximum total of 191. Class B first octet range is 128 through 191.
Class C: The first and second bits in the first octet become 1s. The third bit must remain a 0. The remaining five bits can be a 1, giving a maximum total of 223. Class C first octet range is 192 through 223.
How many usable hosts?
To determine the number of usable hosts, use the formula (i.e.).
Subnet Mask – CIDR
The subnet determines how many subnets a network will have and, consequently, how many hosts each subnet will have. The mask, when in binary form, will display the bits in 1s and 0s respectively. Those bits that are 1s are considered network/subnet bits, and those bits that are 0s are considered host bits.
When determining how many subnets will be created from a specific mask, consideration of the IP address’s class must be taken. Class A addresses have a default mask of 255.0.0.0; therefore, any 1s after the first octet will be considered subnet bits.
The total number of network and subnet bits equal an address’s prefix. If a Class A address of 10.10.33.46 has a mask of 255.255.224.0, then all of the 1s in the binary form of that mask, which totals 19, would be the prefix. In CIDR notation, the address would be seen as 10.10.33.46/19.
Dotted decimals
IP Addresses are, for human intellect, noted in dotted decimal notation. Computers and other devices see IP addresses in binary: that is, a series of 0s and 1s. However, for human eyes and thinking, it is translated into four octets of