Question

1. A network on the Internet has a subnet mask of 255.255 .248 .0 . What is the maximum number of hosts it can handle? 2. Recap the route aggregation function of CIDR. A router has just been made aware of the routes from the following new IP prefixes: 57.6.96.0/21, 57.6.104.0/21, 57.6.112.0/21, and 57.6.120.0/21. If all of them use the same outgoing line, can they be aggregated? If so, to what? If not, why not? 3. A large number of consecutive IP addresses are available starting at 128.208.0.0. Suppose that four organizations, A, B, C, and D, request 4000, 2000, 4000, and 8000 addresses, respectively, and in that order. For each of these, give the first IP address assigned, the last IP address assigned, and the mask in the w⋅x⋅y⋅z/s notation.

Answer 1

The network can handle 8190 hosts. CIDR route aggregation allows the four listed IP prefixes to be combined to 57.6.96.0/20. Provided IPs and masks for organizations A, B, C, and D are 128.208.0.0/20, 128.208.16.0/21, 128.208.24.0/20, and 128.208.40.0/18 respectively.

Step-by-step explanation:

The maximum number of hosts that a network with a subnet mask of 255.255.248.0 can handle is calculated by looking at the number of bits used for the host portion of the address. In this case, there are 13 bits available for the hosts (since the mask is /19 in CIDR notation). Therefore, the maximum number of hosts is 213 - 2, which equals 8190 hosts.

CIDR route aggregation function allows networks with contiguous address blocks to be represented as a single routing table entry. For the IP prefixes 57.6.96.0/21, 57.6.104.0/21, 57.6.112.0/21, and 57.6.120.0/21, they all can be aggregated because they form a consecutive block and can be represented as 57.6.96.0/20.

For the allocation of a large block of IP addresses starting at 128.208.0.0:

• Organization A gets 128.208.0.0 to 128.208.15.255 with the mask 128.208.0.0/20 (4096 addresses).
• Organization B gets 128.208.16.0 to 128.208.23.255 with the mask 128.208.16.0/21 (2048 addresses).
• Organization C gets 128.208.24.0 to 128.208.39.255 with the mask 128.208.24.0/20 (4096 addresses).
• Organization D gets 128.208.40.0 to 128.208.63.255 with the mask 128.208.40.0/18 (16384 addresses).