PRACTICAL

• What does the Domain Name Service (DNS) do?

  It translates URLs into IP addresses using Domain Name Resolution.
• Why must the DNS database be available at all times?

  Because networks would not be able to communicate using URLs without it.
• How many dedicated servers are usually present per subsection of the domain?

  At least two dedicated servers.
• How can you speed up access times if Domain Name Resolution is slow?

  By adding commonly used IP addresses and Domain Names to your hosts file.
• What command can be used to get a domain name from an IP address?

  nslookup.
• What is the purpose of the website http://www.kloth.net/services/nslookup.php?

  It serves as a backup for nslookup if command prompts are blocked.
• What is an IP address?

  A numerical label assigned to each device in a computer network.
• How is an IP address structured?

  It is separated into four octets.
• What is the value range for each octet in an IP address?

  Each octet can have a value between 0 and 255.
• What does the host portion of an IP address uniquely identify?

  It uniquely identifies a particular device attached to that link.
• What does the network portion of an IP address identify?

  It identifies a physical or logical link common to all devices attached to that link.
• What are the classes of IP addresses and their details?

  • Class A: Supports 16 million hosts on 127 networks (0.0.0.0 to 126.255.255.255).
  • Class B: Supports 65,000 hosts on 16,000 networks (128.0.0.0 to 191.255.255.255).
  • Class C: Supports 254 hosts on 2 million networks (192.0.0.0 to 223.255.255.255).
  • Class D: Reserved for multicast groups (224.0.0.0 to 239.255.255.255).
• What is the loopback address in the range of IP addresses?

  127.0.0.1.
• What does the range 255.255.255.255 do?

  It broadcasts to all hosts on the local network.
• What is a limitation of the original idea of IP addresses?

  The network identifier was supposed to correspond to one physical network.
• Why is the block allocation method of distributing IP addresses inefficient?

  Many allocated IP addresses in a block remain unused.
• What happens if a tiny network with only two hosts uses an entire class C block of addresses?

  It wastes 253 addresses.
• What is the consequence of having a large number of networks on routers?

  The forwarding tables kept by routers become very large and expensive.
• What is the new system that uses 128-bits for the address?

  IPv6.
• What is a subnet?

  A block of IP addresses divided between several physical networks.
• What is an advantage of using a subnet?

  It increases security by separating networks.
• Why must networks grouped in a subnet be physically close to each other?

  Because Internet routers assume all subnets will be on the same logical network.
• What is a subnet mask?

  A way of saying which bits to ignore in an IP address when looking for a match.
• If the subnet mask is 255.255.240.0, which part of the IP address is ignored?

  The last octet of the IP address.
• What does a binary 1 in a subnet mask indicate?

  It tells the router to treat that part of the IP address as the network identifier.
• How many subnets does a Class B IP Address divided with a subnet mask of 255.255.240.0 create?

  It divides into 16 subnets.
• What does a binary 0 in a subnet mask indicate?

  It tells the router to treat that part of the IP address as the host identifier.
• What does the subnet mask tell internal routers?

  Whether to route a packet within the subnet or to send it to another subnet.
• What does CIDR stand for?

  Classless Inter Domain Routing.
• What is the purpose of CIDR?

  To use the 32-bit IP address space more efficiently.
• How does CIDR allocate parts of an octet?

  It allows part of an octet to be allocated to a network instead of a whole block.
• What does a CIDR address look like?

  It looks like this: 192.30.250.0/18.
• What does the second part of a CIDR address denote?

  It denotes that the first 18 bits are the network part of the address.
• What is a disadvantage of CIDR?

  It fragments the address space, making routing packets more complex.
• What are the key points about IP address classes and their limitations?

  • Class A: 16 million hosts, inefficient for small networks.
  • Class B: 65,000 hosts, inefficient for networks slightly over 255 hosts.
  • Class C: 254 hosts, inefficient for tiny networks.
  • Class D: Reserved for multicast groups.
  • IPv6 developed to address limitations of IPv4.