C-2 User’s Reference Guide

IP addresses indicate both the identity of the network and the identity of the individual host on the network. The number of bits used for the network number and the number of bits used for the host number can vary, as long as certain rules are followed. The local network manager assigns IP host numbers to individual machines.

IP addresses are maintained and assigned by the InterNIC, a quasi-governmental organization now increasingly under the auspices of private industry.

Note: It’s very common for an organization to obtain an IP address from a third party, usually an Internet service provider (ISP). ISPs usually issue an IP address when they are contracted to provide Internet access services.

The InterNIC (the NIC stands for Network Information Center) divides IP addresses into several classes. Classes A, B, and C are assigned to organizations who request addresses. In Class A networks, the first byte of an IP address is reserved for the network portion of the address. Class B networks reserve the first two bytes of an IP address for the network address. Class C networks reserve the first three bytes of an IP address for the network address. In all cases, a network manager can decide to use subnetting to assign even more bits to the network portion of the IP address, but never less than the class requires. The following section gives more information on subnetting.

Class A networks have a small number of possible network numbers, but a large number of possible host numbers. Conversely, Class C networks have a small number of possible host numbers, but a large number of possible network numbers. Thus, the InterNIC assigns Class A addresses to large organizations that have very large numbers of IP hosts, while smaller organizations, with fewer hosts, get Class B or Class C addresses. You can tell the various classes apart by the value of the first (or high-order) byte. Class A networks use values from 1 to 127, Class B networks use values from 128 to 191, and Class C networks use values from 192 to 223. The following table summarizes some of the differences between Class A, B, and C networks.

 

 

Number of

Number of

 

 

Class

First byte

networks

hosts

Format of address

Example

possible per

possible per

(without subnetting)

 

 

 

 

 

class

network

 

 

 

 

 

 

 

 

 

 

 

 

 

 

A

1-127

127

16,777,214

net.host.host.host

97.3.14.250

 

 

 

 

 

 

B

128-191

16,384

65,534

net.net.host.host

140.100.10.11

 

 

 

 

 

 

C

192-223

2,097,152

254

net.net.net.host

197.204.13.7

 

 

 

 

 

 

Subnets and subnet masks

Often an entire organization is assigned only one IP network number. If the organization has several IP networks connected together with IP routers, the network manager can use subnetting to distinguish between these networks, even though they all use the same network number. Each physical network becomes a subnet with a unique subnet number.

Subnet numbers appear within IP addresses, along with network numbers and host numbers. Since an IP address is always 32 bits long, using subnet numbers means either the network number or the host numbers must use fewer bits, in order to leave room for the subnet numbers. Since the InterNIC assigns the network number proper, it should not change, so the subnet numbers must be created out of bits that would otherwise be part of the host numbers.

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Netopia R2121 manual Subnets and subnet masks

R2121 specifications

The Netopia R2121 is a powerful and versatile router designed for both home and office environments, providing seamless connectivity and robust performance for various networking needs. This device offers a range of features and technologies that cater to the demands of modern users seeking reliable internet access, speed, and security.

One of the standout characteristics of the Netopia R2121 is its dual-band technology, which operates on both the 2.4 GHz and 5 GHz frequency bands. This capability allows users to enjoy faster speeds and less interference, as the 5 GHz band is typically less congested than the traditional 2.4 GHz band. With the ability to support multiple devices simultaneously, the R2121 ensures that users can stream videos, play online games, and conduct video conferences without experiencing lag or connectivity issues.

The router is equipped with advanced security features, including WPA3 encryption, which provides enhanced protection against unauthorized access and data breaches. The R2121 also supports a robust firewall system that guards against external threats, ensuring that the user's network remains secure. Additionally, the router includes parental controls, allowing users to manage and restrict internet access for specific devices or set time limits for usage, making it an excellent choice for families.

Another significant advantage of the Netopia R2121 is its extensive coverage area. With high-gain antennas and advanced beamforming technology, the router can deliver strong and stable Wi-Fi signals even in larger homes or office spaces. This technology focuses the Wi-Fi signal directly toward connected devices, minimizing dead zones and improving overall connectivity.

The R2121 also supports both IPv4 and IPv6, ensuring compatibility with current and future internet technologies. This forward-thinking design makes it a future-proof solution for users looking to invest in a reliable router.

In terms of setup and management, the Netopia R2121 features a user-friendly web interface that allows users to easily customize settings, monitor network performance, and manage connected devices. The inclusion of mobile app support further enhances the user experience, enabling remote monitoring and control of the network from anywhere.

Overall, the Netopia R2121 stands out as a robust and reliable router that combines advanced features, enhanced security, and excellent performance, making it an ideal choice for home and business users alike. With its focus on delivering seamless connectivity and comprehensive management options, the R2121 is well-suited for today's connected lifestyles.