![]() If you are using traditional Class A, B or C networks, the VPN 5000 Manager will automatically calculate the value for you. If you have a router with more than one interface, the network (+ subnet) portions of each port's IP address must be different. For example, if your ISP tells you your network portion is 198.41.9, you could assign an interface to 198.41.9.1. Assign the router interface a unique (i.e. Use the network portion you were given by your administrator or ISP. Line 5 shows what happens when a Class C network has been subnetted. Note in line 4 the change in the third octet between network address and broadcast address. The last two are less traditional, "real world" examples. The first three entries are traditional Class A, B and C network addresses and use traditional masks. Table A-4 shows some examples of broadcast addresses. Most often, the broadcast address is the last address in the network (or subnet) with the host portion being all 1's binary (some networks use 0.0.0.0 or 255.255.255.255, however.). Address Resolution Protocol (ARP) packets and routing information are examples of packets sent to the broadcast address. All devices "listen" for broadcasts in addition to their own address. The broadcast address is the address to which devices send packets meant for all other devices. The same idea can be extended to Class A and Class B networks. As you use more bits to represent the network portion, fewer bits are left to use as host addresses. With each mask above, the 1s in the binary value represent the network portion, and the 0s represent the host portion (128 is 10000000, 192 is 11000000, etc.). The highest address in each range (255 in the traditional C range) is also not shown, and is the broadcast address for the subnet. The lowest calculated address in each range (0 in the traditional C range) is not shown, cannot be used, and is skipped in the chart. In each case, the part of the address not used for the network portion is left as the host portion. How much of any given address is the network part and how much is the host part is determined by the "class" of the network. ![]() If your network is, or will be, connected to the Internet, you will need to get a unique network address from your ISP or network administrator. In the case of the Internet, this uniqueness is made possible by indirectly getting all network portion assignments through a central clearinghouse called the Network Information Center or "NIC." The NIC assigns blocks of addresses to Internet Service Providers (ISPs), who then assign these addresses to their customers. 198.41.12.151, 255.255.255.0, and 198.41.12.255).Įvery IP address is really made up of two pieces: a "network" portion, which tells routers what group of devices a packet should go to (e.g., any, a campus, etc.) and a "host" portion which tells routers what specific device among that group the packet should go to.īy examining the destination address in an IP packet that must be forwarded, and by using information that has either been statically configured or dynamically gathered from other routers, any router can determine the optimal path for forwarding packets from one group to another.Įach group of devices on an IP internet needs to have a unique network portion, and each device within that group also needs a unique host portion. You will usually see each of these numbers written as four "octets" (e.g. In particular, Douglas Comer's Internetworking with TCP/IP (Prentice Hall) is one of the standard references and provides a wealth of information on the subject.Įach device on an IP network requires 3 different pieces of information in order to correctly communicate with other devices on the network: an IP address, a subnet mask, and a broadcast address. For more in-depth information, there are a number of excellent references. This is a very brief introduction to IP networking. Network/Protocol Addressing and Virtual Interfaces ![]() Multiport Bridges/Switches and "Bridge Groups" Non-extended and Extended AppleTalk Networks
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