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| | IP Address Classes |
 | | On the other hand, a binary IP address of 00000000.00000000.00000000.00000000 will be, in decimal, 0.0.0.0, which in a routing table represents an unknown network or host, and is typically used to designate the default gateway of last resort. |
 | | Generally, there will be only as many IP addresses as may be designated by the three most common classes of IP addresses, A, B and C. There are two more classes, D and E, but they are used for multicast and experimental purposes respectively, so we won't get into those here. |
 | | The default subnet mask for a Class A IP address is 255.0.0.0; Class B is 255.255.0.0 and Class C is 255.255.255.0. |
| www.cramsession.com /articles/files/ip-address-classes-9162003-1514.asp (1057 words) |
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