Deck 4 - IP Addressing

What is the address range for Class A addresses?

1.0.0.0 – 126.255.255.255

What is the address range for Class B addresses?

128.0.0.0 – 191.255.255.255

What is the address range for Class C addresses?

192.0.0.0 – 223.255.255.255

What is the default subnet mask for a Class A address?

255.0.0.0 (/8)

What is the default subnet mask for a Class B address?

255.255.0.0 (/16)

What is the default subnet mask for a Class C address?

255.255.255.0 (/24)

What are the three private IP address ranges?

10.0.0.0–10.255.255.255 (Class A)

172.16.0.0–172.31.255.255 (Class B)

192.168.0.0–192.168.255.255 (Class C)

What is the loopback address range and its purpose?

127.0.0.0–127.255.255.255, used by a host to test communication with itself (e.g., 127.0.0.1)

What type of communication do multicast addresses provide and what is the IP range?

One-to-many, service-based group messaging. Class D address range from 224.0.0.0 - 239.255.255.255

What is an APIPA address and what range does it use?

Automatic Private IP Addressing — self-assigned by Windows when DHCP fails and ensures that devices can still communicate within a local network; uses 169.254.0.1–169.254.255.254 for local-only communication

What class is the IP address 10.0.5.1?

Class A (private)

What class is the IP address 45.22.10.5?

Class A (public)

What class is the IP address 1.1.1.1?

Class A (public)

What class is the IP address 126.5.5.5?

Class A (public) — near the top edge of the Class A range (1.0.0.0–126.255.255.255)

What class is the IP address 128.10.5.6?

Class B (public)

What class is the IP address 172.16.0.5?

Class B (private)

What class is the IP address 172.31.255.254?

Class B (private) — top edge of the private Class B range

What class is the IP address 191.255.0.1?

Class B (public) — top edge of the Class B range (128.0.0.0–191.255.255.255)

What class is the IP address 192.0.2.5?

Class C (public)

What class is the IP address 192.168.1.1?

Class C (private)

What class is the IP address 192.168.254.10?

Class C (private)

What class is the IP address 223.255.255.0?

Class C (public) — top edge of the Class C range (192.0.0.0–223.255.255.255)

What class is the IP address 224.0.0.5?

Not a host class — it's a Multicast address (224.0.0.0 range)

What class is the IP address 127.0.0.1?

Not a host class — it's a Loopback address (127.0.0.0–127.255.255.255), used for testing a NIC

What class is the IP address 169.254.10.5?

Not a class-based address — it's an APIPA address (169.254.0.1–169.254.255.254), self-assigned when DHCP fails

Is 10.44.2.9 a public or private IP address?

Private (falls in the 10.0.0.0–10.255.255.255 Class A private range)

Is 172.20.5.3 a public or private IP address?

Private (falls in the 172.16.0.0–172.31.255.255 Class B private range)

Is 172.32.5.3 a public or private IP address?

Public — it's just outside the private range, which stops at 172.31.255.255

Is 192.168.100.5 a public or private IP address?

Private (falls in the 192.168.0.0–192.168.255.255 Class C private range)

Is 192.169.1.5 a public or private IP address?

Public — it's outside the private 192.168.0.0/16 range

Is 8.8.8.8 a public or private IP address?

Public

Is 74.125.224.72 a public or private IP address?

Public

Is 11.0.0.1 a public or private IP address?

Public — the private Class A range only covers 10.0.0.0–10.255.255.255

Is 169.254.1.1 a public or private IP address?

Neither — it's an APIPA address, self-assigned locally when DHCP fails; not routable

What are the three private IP address ranges?

10.0.0.0–10.255.255.255 (Class A), 172.16.0.0–172.31.255.255 (Class B), 192.168.0.0–192.168.255.255 (Class C)

What does CIDR stand for?

Classless Inter-Domain Routing

What is CIDR notation?

A method of specifying an IP address and its associated subnet mask using a slash ("/") followed by a number representing how many bits of the address are the network portion

What is the subnet mask for /24?

255.255.255.0

What is the subnet mask for /16?

255.255.0.0

What is the subnet mask for /8?

255.0.0.0

What CIDR notation corresponds to a subnet mask of 255.255.255.0?

/24

What CIDR notation corresponds to a subnet mask of 255.255.0.0?

/16

What CIDR notation corresponds to a subnet mask of 255.0.0.0?

/8

How many network bits does /24 represent, and what does that mean for 192.168.1.0/24?

24 bits — the first 24 bits (192.168.1) are the network portion, leaving 8 bits for hosts

What does CIDR replace, and why was that method inefficient?

CIDR replaces classful addressing, which used fixed default masks per class (A, B, C) and wasted large amounts of address space

What is VLSM?

Variable-Length Subnet Mask — allows subnets within the same network to have different mask sizes for more efficient address allocation

What is the subnet mask for a Class C network subnetted to /25?

255.255.255.128

How many subnets are created when you subnet a Class C (/24) network to /25?

2 subnets (borrowing 1 host bit)

How many total addresses are in each /25 subnet?

128 addresses

How many usable host addresses are in each /25 subnet, and why?

126 — 128 total addresses minus 1 for the network address and 1 for the broadcast address

If 192.168.1.0/24 is subnetted into two /25 networks, what are the two subnet addresses?

192.168.1.0/25 and 192.168.1.128/25

What is the usable host range for the subnet 192.168.1.0/25?

192.168.1.1 – 192.168.1.126

What is the broadcast address for the subnet 192.168.1.0/25?

192.168.1.127

What is the usable host range for the subnet 192.168.1.128/25?

192.168.1.129 – 192.168.1.254

What is the broadcast address for the subnet 192.168.1.128/25?

192.168.1.255

Why would you subnet a Class C network into /25 blocks instead of leaving it as /24?

To split one broadcast domain into two smaller network segments, improving address efficiency, traffic isolation, and security

You have the IP address 192.168.30.0/25. What is the number of networks?

2^1 = 2 (1 bit borrowed from the host portion to subnet a /24 into /25)

You have the IP address 192.168.30.0/25. What is the number of hosts per network?

2^7 - 2 = 126 (7 host bits remain; subtract 2 for network ID and broadcast)

You have the IP address 192.168.30.0/25. What are the two network IDs?

192.168.30.0 and 192.168.30.128

You have the IP address 192.168.30.0/25. What is the first usable IP in each network?

192.168.30.1 and 192.168.30.129

You have the IP address 192.168.30.0/25. What is the last usable IP in each network?

192.168.30.126 and 192.168.30.254

You have the IP address 192.168.30.0/25. What is the broadcast IP for each network?

192.168.30.127 and 192.168.30.255

What is the Layer 3 broadcast address?

255.255.255.255

What is the Layer 2 broadcast address?

FF:FF:FF:FF:FF:FF