USE AN ASSIGNED IP NETWORK ID OR CHOOSE A PRIVATE IP ADDRESS, AND T...

3. Use an assigned IP network ID or choose a private IP address, and then deter-mine how to subnet your network.As an example, suppose that we have 55 employees in one location, with 12 IP-basednetwork printers, 6 servers, and 1 Internet refrigerator that orders the groceries in the breakarea when the stock is depleted. Our IP address block assignment provided by our InternetService Provider (ISP) is 204.74.9.0/24. All the employees are currently located in onelarge, central area on the same floor. Since we have no physical boundaries to overcome, weuse the default subnet mask.This would provide us with one network and 8 bits in the hostportion of our address.The 8 bits give us 256 hosts, but the first host is 0, which refers toour network, and the last host is the broadcast address for the network, 255. Remember theformula is 2

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– 2, where nis the number of bits available for host IDs. So, 2

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– 2 = 256 – 2= 254 hosts per network. Since we have 74 hosts and one router, that is a total of 75 hostIDs.We have plenty of room for growth, and the scheme is simple.The first address on our network starts at 204.74.9.1 (remember 0 is “this network”)and continues to 204.74.9.254 with a subnet mask of 255.255.255.0.Table 3.7 shows anexample of the network portion of our address, 204.74.9, and the host portion in the lastoctet, from 1 to 254.

Table 3.7

Breakdown of the Mask for IP Addresses Using a Standard Subnet MaskSource IP Address 204.74.9.21 Destination IP Address 204.74.9.209Subnet Mask 255.255.255.0 Subnet Mask 255.255.255.0|--—— Network ID ——--|. |— Host —| |——— Network ID ——|. |— Host —|