Lecture 5. Network Layer. IPv4 addressing Flashcards
(18 cards)
Q: What are the four basic operations of the network layer?
A:
1. Addressing end devices,
2. encapsulation,
3. routing,
4. de-encapsulation.
Q: Which are the principal network layer protocols?
A: IPv4 and IPv6.
Q: What is an IPv4 address and how many bits does it have?
A: A unique identifier for a device on a network, consisting of 32 bits.
Q: How is an IPv4 address typically represented?
A: In four octets, e.g., 192.168.1.1, each octet being 8 bits.
Q: What is a subnet mask?
A: A sequence that defines which part of an IPv4 address is the network portion and which is the host portion.
Q: How do you identify the network and host portions of an IPv4 address?
A: The network portion corresponds to the subnet mask’s binary “1”s; the remainder are host bits.
Q: What is a prefix length?
A: The number of bits set to “1” in the subnet mask, e.g., /24 means 24 “1”s.
Q: Name the legacy IPv4 address classes and their use.
A: Class A (large networks), Class B (medium), Class C (small), Class D (multicast), Class E (experimental).
Q: What replaced classful addressing and why?
A: Classless addressing (CIDR) for better address utilization.
Q: What are network, broadcast, first and last usable addresses?
A:
- Network address: the first address in a subnet
- Broadcast address: the last address in a subnet
- First usable: one after the network address
- Last usable: one before the broadcast address
Q: Explain Unicast, Multicast, and Broadcast addresses.
A:
- Unicast: one recipient
- Multicast: group of addresses (224.0.0.0 to 239.255.255.255)
- Broadcast: sent to all devices in a network (last address in subnet)
Q: What is VLSM and why is it important?
A: Variable Length Subnet Masking allows subnets of different sizes, optimizing address allocation.
Q: Steps for VLSM subnetting?
A:
1. Find subnet mask/prefix length.
2. Identify network address.
3. Find first address.
4. Find last address.
5. Find broadcast address.
Q: What are private and public IPv4 addresses?
A:
Private: usable only within LAN, not routable on the Internet.
Public: globally routable.
Q: What is a default gateway?
A: The router device IP on a LAN used to send traffic outside the local network.
Q: What is the special use and range for loopback and link-local addresses?
A:
Loopback: 127.0.0.0/8 (used to check a device’s own TCP/IP stack)
Link-local: 169.254.0.0/16 (automatic addressing when DHCP fails)
Q: What is ICMP and what is it used for?
A: Internet Control Message Protocol, used for error and diagnostic messages (e.g., destination unreachable, time exceeded).
Q: What does the traceroute tool use to determine packet paths?
A: ICMP Time Exceeded messages and decrementing TTL (Time To Live) field.
