Assumptions for Network Setup The TCP/IP networks can also be divided by public and private IP addresses: Your public IP address is assigned to you by your Internet service provider (ISP). In fact, this IP address is allocated to the ISP by the Internet Assigned Numbers Authority (IANA - http://www.iana.org). It’s your public IP address that identifies you on the Internet. Private IP addresses are those (like the addresses used in the diagram above) that identify a device within a private or non-Internet connected network. There are three TCP/IP network address ranges reserved for use in private networks: 10.0.0.0-10.255.255.255, 172.16.0.0-172.31.255.255, and 192.168.0.0-192.168.255.255. A netmask is a 32-bit string that hides the network part of an IP address, so that only the host (computer) part of the address remains. For example, the netmask 255.255.255.0 looks like an IP address, but in fact hides the first 24 bits of the IP address so that only the last 8 bits remain (recall that 255 is the decimal representation of the binary 11111111). Hence, the netmask 255.255.255.0 is commonly used for Class C IP addresses to reveal the specific host computer address publicly. There are a few more definitions that will be useful here: A gateway is a host that is connected to two or more physical networks, and hence allows messages to switch between them. The term hostname refers to the unique name of the machine, so that it can identify itself on the network. Finally, the domain name system (or DNS) is a distributed database that translates domain names into IP addresses and vice versa. For example, DNS translates the domain name www.linux4biz.net to the IP address 212.69.200.83. With all that in mind, let’s return to those two machines on our network - the Red Hat Linux 9 server machine and the Windows 2000 client laptop machine. Here are the network configuration settings we used for those two machines in this chapter. The Red Hat Linux 9 server machine is set up as a firewall and router, and has Internet connectivity. Over the course of the chapter we’ll show how it can be configured as a file server, printer server, DHCP server, FTP server, web server, or mail server: Server Value Operating system Red Hat Linux 9 IP address 192.168.0.99 Netmask 255.255.255.0 Hostname linux4biz The laptop is a simple client machine, designed for an end-user and (potentially) sharing resources with other similar machines on the network: Setting Value Purpose A Client laptop system to be used to share resources configured on Linux server Operating system Windows 2000 Professional IP address 192.168.0.132 Netmask 255.255.255.0 269
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