User manual NETGEAR WGT624 Reference Manual

[. . . ] Reference Manual for the 108 Mbps Wireless Firewall Router WGT624 v3 NETGEAR, Inc. 4500 Great America Parkway Santa Clara, CA 95054 USA 202-10090-01 April 2005 202-10090-01, April 2005 © 2005 by NETGEAR, Inc. Microsoft, Windows, and Windows NT are registered trademarks of Microsoft Corporation. Other brand and product names are registered trademarks or trademarks of their respective holders. [. . . ] Class B addresses are in this range: 128. 1. x. x to 191. 254. x. x. · Class C Class C addresses can have 254 hosts on a network. Class C addresses use 24 bits for the network address and eight bits for the node. They are in this range: 192. 0. 1. x to 223. 255. 254. x. · Class D Class D addresses are used for multicasts (messages sent to many hosts). Class D addresses are in this range: 224. 0. 0. 0 to 239. 255. 255. 255. · Class E Class E addresses are for experimental use. B-3 Network, Routing, Firewall, and Basics 202-10090-01, April 2005 Reference Manual for the 108 Mbps Wireless Firewall Router WGT624 v3 This addressing structure allows IP addresses to uniquely identify each physical network and each node on each physical network. For each unique value of the network portion of the address, the base address of the range (host address of all zeros) is known as the network address and is not usually assigned to a host. Also, the top address of the range (host address of all ones) is not assigned, but is used as the broadcast address for simultaneously sending a packet to all hosts with the same network address. Netmask In each of the address classes previously described, the size of the two parts (network address and host address) is implied by the class. This partitioning scheme can also be expressed by a netmask associated with the IP address. A netmask is a 32-bit quantity that, when logically combined (using an AND operator) with an IP address, yields the network address. For instance, the netmasks for Class A, B, and C addresses are 255. 0. 0. 0, 255. 255. 0. 0, and 255. 255. 255. 0, respectively. For example, the address 192. 168. 170. 237 is a Class C IP address whose network portion is the upper 24 bits. When combined (using an AND operator) with the Class C netmask, as shown here, only the network portion of the address remains: 11000000 10101000 10101010 11101101 (192. 168. 170. 237) combined with: 11111111 11111111 11111111 00000000 (255. 255. 255. 0) Equals: 11000000 10101000 10101010 00000000 (192. 168. 170. 0) As a shorter alternative to dotted-decimal notation, the netmask may also be expressed in terms of the number of ones from the left. This number is appended to the IP address, following a backward slash (/), as "/n. " In the example, the address could be written as 192. 168. 170. 237/24, indicating that the netmask is 24 ones followed by 8 zeros. Subnet Addressing By looking at the addressing structures, you can see that even with a Class C address, there are a large number of hosts per network. Such a structure is an inefficient use of addresses if each end of a routed link requires a different network number. It is unlikely that the smaller office LANs would have that many devices. You can resolve this problem by using a technique known as subnet addressing. B-4 Network, Routing, Firewall, and Basics 202-10090-01, April 2005 Reference Manual for the 108 Mbps Wireless Firewall Router WGT624 v3 Subnet addressing allows us to split one IP network address into smaller multiple physical networks known as subnetworks. A Class B address gives us 16 bits of node numbers translating to 64, 000 nodes. Most organizations do not use 64, 000 nodes, so there are free bits that can be reassigned. Subnet addressing makes use of those bits that are free, as shown below. Class B Network Subnet Node 7262 Figure 7-2: Example of Subnetting a Class B Address A Class B address can be effectively translated into multiple Class C addresses. For example, the IP address of 172. 16. 0. 0 is assigned, but node addresses are limited to 255 maximum, allowing eight extra bits to use as a subnet address. The IP address of 172. 16. 97. 235 would be interpreted as IP network address 172. 16, subnet number 97, and node number 235. In addition to extending the number of addresses available, subnet addressing provides other benefits. Subnet addressing allows a network manager to construct an address scheme for the network by using different subnets for other geographical locations in the network or for other departments in the organization. [. . . ] But, using TKIP, WPA-PSK automatically changes the keys at a preset time interval, making it much more difficult for hackers to find and exploit them. The Wi-Fi Alliance will call this, 'WPA-Personal. ' Wi-Fi Protected Access and IEEE 802. 11i Comparison Wi-Fi Protected Access will be forward-compatible with the IEEE 802. 11i security specification currently under development by the IEEE. Wi-Fi Protected Access is a subset of the current 802. 11i draft, taking certain pieces of the 802. 11i draft that are ready to bring to market today, such as its implementation of 802. 1x and TKIP. These features can also be enabled on most existing Wi-Fi CERTIFIED products as a software upgrade. [. . . ]