Section A — 1 Mark Questions
1. What is the size of an IPv4 address? [1 Mark]
Answer: An IPv4 address is 32 bits long.
2. How many bits are in an IPv6 address? [1 Mark]
Answer: An IPv6 address is 128 bits long.
3. Which address class has a leading bit pattern of '110'? [1 Mark]
Answer: Class C addresses.
4. What is the primary purpose of ARP? [1 Mark]
Answer: To map a known IP address to its corresponding physical (MAC) address.
5. What does CIDR stand for? [1 Mark]
Answer: Classless Inter-Domain Routing.
6. In IPv4, what is the address range for Class A? [1 Mark]
Answer: 0.0.0.0 to 127.255.255.255.
7. What is the main function of NAT? [1 Mark]
Answer: To translate private local IP addresses into a single public IP address for internet access.
8. What is RARP used for? [1 Mark]
Answer: To map a physical (MAC) address to an IP address when the device does not know its own IP.
9. What is the default subnet mask for a Class B network? [1 Mark]
Answer: 255.255.0.0.
10. How many address bits are reserved for the host ID in a standard Class A address? [1 Mark]
Answer: 24 bits.
11. Which field in the IPv6 header specifies the upper-layer protocol? [1 Mark]
Answer: The Next Header field.
12. What is a subnet? [1 Mark]
Answer: A logical subdivision of an IP network.
13. Which class is reserved for multicast addressing? [1 Mark]
Answer: Class D.
14. What is the broadcast address for a network with mask 255.255.255.0? [1 Mark]
Answer: The last address in the range, typically ending in .255.
15. What notation is used to represent classless addressing? [1 Mark]
Answer: Slash notation (e.g., /24).
16. Can NAT improve network security? [1 Mark]
Answer: Yes, by hiding internal network structure from the outside world.
17. What is the loopback address in IPv4? [1 Mark]
Answer: 127.0.0.1.
18. Are Class E addresses used for commercial purposes? [1 Mark]
Answer: No, they are reserved for experimental and future use.
19. Does ARP operate at the Data Link or Network layer? [1 Mark]
Answer: It is often considered to operate between the two, but formally sits within the network layer architecture to provide mapping for link layer delivery.
20. What is the benefit of IPv6 addressing space? [1 Mark]
Answer: It provides a significantly larger address space to accommodate the exhaustion of IPv4 addresses.
Section B — 2/3 Mark Questions
1. Distinguish between Classful and Classless addressing. [2 Marks]
Answer: Classful addressing divides IP addresses into fixed-size classes (A, B, C, D, E) based on the first few bits. Classless addressing (CIDR) removes these fixed boundaries, allowing for variable-length subnet masking for more efficient address allocation.
2. Explain the concept of Subnetting. [3 Marks]
Answer: Subnetting is the process of partitioning a single physical network into multiple logical subnetworks. This is achieved by borrowing bits from the host portion of an IP address to represent a subnet ID. It improves network performance, reduces broadcast traffic, and increases security.
3. Briefly explain how NAT works. [2 Marks]
Answer: NAT sits at the edge of a network and maintains a translation table. It replaces private source IP addresses in outgoing packets with a public IP address and maps returning packets back to the original internal IP addresses using port numbers.
4. What are the primary differences between IPv4 and IPv6? [3 Marks]
Answer: 1) IPv4 uses 32-bit addresses, while IPv6 uses 128-bit addresses. 2) IPv6 includes built-in security features and better support for Quality of Service. 3) IPv6 simplifies the header structure, which improves packet processing efficiency by routers.
5. Describe the role of the ARP table. [2 Marks]
Answer: The ARP table is a cache used by devices to store the mapping of IP addresses to physical MAC addresses. It prevents the need to send an ARP request broadcast for every single outgoing packet to a known destination.
6. Why was RARP developed, and why is it largely obsolete? [3 Marks]
Answer: RARP was developed to allow diskless workstations to discover their own IP addresses upon booting. It is obsolete because it has been replaced by more versatile protocols like BOOTP and DHCP, which provide additional configuration details like subnet masks and default gateways.
7. List the address ranges for Classes A, B, and C. [3 Marks]
Answer: Class A: 1-127 (first octet). Class B: 128-191 (first octet). Class C: 192-223 (first octet).
8. What is an ARP request? [2 Marks]
Answer: An ARP request is a broadcast message sent by a source device asking, 'Who has this IP address?' with the intent of obtaining the hardware MAC address of the target machine.
9. How does the IPv6 header structure differ from IPv4? [3 Marks]
Answer: The IPv6 header is fixed at 40 bytes, whereas the IPv4 header is variable (20-60 bytes). IPv6 eliminates fields like the checksum and fragmentation fields, relying on upper-layer protocols for those functions, which speeds up router processing.
10. Explain the purpose of a Subnet Mask. [2 Marks]
Answer: A subnet mask is a 32-bit value used to distinguish the network portion of an IP address from the host portion. It allows the device to determine if the destination IP is on the local network or a remote network.
Section C — 5 Mark Questions
1. Explain the process of IPv4 Classful Addressing and its limitations. [5 Marks]
Introduction
Classful addressing was the original design for IPv4, categorizing addresses into specific classes to define network and host portions.
Classes
- Class A: Uses first 8 bits for network; supports very large networks.
- Class B: Uses first 16 bits for network; supports medium networks.
- Class C: Uses first 24 bits for network; supports small networks.
- Class D and E: Reserved for multicasting and experimentation respectively.
Limitations
The main limitation is address depletion and inefficiency. In a Class A network, over 16 million addresses are assigned to a single organization, leading to massive wastage if the organization does not need that many. This rigid structure resulted in the premature exhaustion of the IPv4 address space.
2. Discuss the mechanism and advantages of Network Address Translation (NAT). [5 Marks]
Mechanism
NAT operates at the boundary of a local network, typically on a router or firewall. When an internal host sends a packet to the internet, the NAT device replaces the internal (private) source IP address with its own public IP address. It records this mapping in a NAT translation table. When the response returns, the NAT device uses this table to route the packet back to the original internal host.
Advantages
- Conserves public IP addresses by allowing many private hosts to share one public IP.
- Enhances security by masking the internal network topology from external threats.
- Provides flexibility in renumbering internal networks without needing to change public IP configurations.
- Simplifies internet connectivity for private internal systems.
3. Elaborate on the Address Resolution Protocol (ARP) process. [5 Marks]
Working Principle
ARP is essential for local communication. When a host wants to send data to another device on the same LAN, it knows the destination IP address but needs the destination MAC address. 1. The source host checks its local ARP cache. 2. If not found, it broadcasts an ARP request packet to the entire network. 3. Every device on the network receives the packet, but only the host with the matching IP address replies. 4. The target sends an ARP reply containing its MAC address directly to the source. 5. The source updates its ARP cache with the new mapping.
Significance
Without ARP, devices would have no way to bridge the gap between logical (IP) addressing and physical (MAC) hardware addressing, making data link layer communication impossible in Ethernet networks.
4. Describe the structure and benefits of IPv6 addressing. [5 Marks]
Structure
IPv6 uses a 128-bit address, typically represented as eight groups of four hexadecimal digits separated by colons. It includes a hierarchical structure that helps improve routing efficiency. The address consists of the Network Prefix (routing) and the Interface ID (host identifier).
Benefits
- Massive Address Space: Provides 3.4 x 1038 addresses, effectively eliminating address exhaustion.
- Simplified Header: Reduced overhead due to the removal of unnecessary fields like checksums.
- Autoconfiguration: Supports stateless address autoconfiguration (SLAAC), allowing devices to generate their own addresses automatically.
- Enhanced Support: Built-in support for security (IPsec) and improved quality of service (QoS) features for multimedia streaming.
5. Explain the concept of Subnetting and how it optimizes network performance. [5 Marks]
Explanation
Subnetting is the logical segmentation of a single IP network into smaller segments. By adjusting the subnet mask, network administrators can designate how many bits are used for the network and how many are used for hosts. This is done by 'borrowing' bits from the host part to extend the network prefix.
Optimization
- Reduced Broadcast Traffic: By creating smaller domains, broadcast traffic is confined to the local subnet, reducing the load on all hosts.
- Increased Security: Access Control Lists (ACLs) can be applied between subnets to restrict or monitor traffic flow.
- Organizational Efficiency: Allows networks to be divided based on departments, geography, or functionality.
- Scalability: Network administrators can manage multiple smaller subnets more easily than one massive, unmanageable network block.