3Com OFFICE CONNECT CABLE/DSL SECURE GATEWAY 3CR856-95 User Manual

Contents

73IP A DDRESSINGThe Internet Protocol SuiteThe Internet protocol suite consists of a well-defined set ofcommunications protocols and several standard applicationprotocols. Transmission Control Protocol/Internet Protocol (TCP/IP)is probably the most widely known and is a combination of twoof the protocols (IP and TCP) working together. TCP/IP is aninternationally adopted and supported networking standard thatprovides connectivity between equipment from many vendorsover a wide variety of networking technologies.IP Addresses and Subnet MasksEach device on your network must have a unique IP address tooperate correctly. An IP address identifies the address of thedevice to which data is being sent and the address of thedestination network. IP addresses have the format n.n.n.x wheren is a decimal number between 0 and 255 and x is a numberbetween 1 and 254 inclusive.However, an IP Address alone is not enough to make your deviceoperate. In addition to the IP address, you need to set a subnetmask. All networks are divided into smaller sub-networks and asubnet mask is a number that enables a device to identify thesub-network to which it is connected.For your network to work correctly, all devices on the networkmust have:■ The same sub-network address.■ The same subnet mask.The only value that will be different is the specific host devicenumber. This value must always be unique.An example IP address is ‘192.168.100.8’. However, the size ofthe network determines the structure of this IP Address. In usingthe Gateway, you will probably only encounter two types of IPAddress and subnet mask structures.Type OneIn a small network, the IP address of ‘192.168.100.8’ is split intotwo parts:■ Part one (‘192.168.100’) identifies the network on which thedevice resides.■ Part two (‘.8’) identifies the device within the network.This type of IP Address operates on a subnet mask of‘255.255.255.0’.See Table 3 for an example about how a network with three PCsand a Cable/DSL Secure Gateway might be configured.Table 3 IP Addressing and Subnet Masking in a Small NetworkDevice IP Address Subnet MaskPC 1 192.168.100.8 255.255.255.0PC 2 192.168.100.33 255.255.255.0PC 3 192.168.100.188 255.255.255.0Cable/DSLSecure Gateway192.168.100.72 255.255.255.0dua08 569-5aaa02.bo o k Pag e 7 3 Thursday , No vem ber 7 , 2002 3:09 PM