Cabling and IP Adresses

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  T568A AND T568B  T568A and T568B are the two color codes used for wiring eight-position RJ45 modular plugs. Both are allowed under the ANSI/TIA/EIA wiring standards. The only difference between the two color codes is that the orange and green pairs are interchanged.  T568A wiring pattern is recognized as the preferred wiring pattern for this standard because it provides backward compatibility to both one pair and two pair USOC wiring schemes.  The T568B standard matches the older ATA&T 258A color code and is the most widely used wiring scheme. It is also permitted by the ANSI/TIA/EIA standard, but it provides only a single pair backward compatibility to the USOC wiring scheme.  The U.S. Government requires the use of the preferred T568A standard for wiring done under federal contracts.  COLOR CODE FOR CROSSOVER Making a crossover cable  To make an RJ45 crossover cable, buy a  patch cable  , split it in the middle, and then reconnect the wires as follows: End 1 End 2 Name # Color Name # Color  TD+ 1 White/Green RD+ 3 White/Orange  TD- 2 Green RD- 6 orange RD+ 3 White/Orange TD+ 1 White/Green Not used 4 Blue Not used 4 Blue Not used 5 White/Blue Not used 5 White/Blue RD- 6 orange TD- 2 Green Not used 7 White/Brown: Not used 7 White/Brown: Not used 8 Brown Not used 8 Brown  IP CLASSIFICATIONS IP address classes  The Internet community originally defined five address classes to accommodate networks of varying sizes. Microsoft TCP/IP supports class A, B, and C addresses assigned to hosts.  The class of address defines which bits are used for the network ID and which bits are used for the host ID. It also defines the possible number of networks and the number of hosts per network. Class 1 st  Octet Decimal Range 1 st  Octet High Order Bits Network/Host ID (N=Network, H=Host) Default Subnet Mask Number of Networks Hosts per Network (Usable Addresses) A 1  –   126* 0 N.H.H.H 126 (2 7    –   2) 16,777,214 (2 24    –   2) B 128  –   191 10 N.N.H.H 16,382 (2 14    –   2) 65,534 (2 16    –   2) C 192  –   223 110 N.N.N.H 2,097,150 (2 21    –   2) 254 (2 8    –   2) D 224  –   239 1110 Reserved for Multicasting E 240  –   254 1111 Experimental; used for research Note:  Class A addresses to cannot be used and is reserved for loopback and diagnostic functions. Private IP Addresses Class Private Networks Subnet Mask Address Range A - B - - C - Class A  Class A addresses are assigned to networks with a very large number of hosts. The high-order bit in a class A address is always set to zero. The next seven bits (completing the first octet) complete the network ID. The remaining 24 bits (the last  three octets) represent the host ID. This allows for 126networks and 16,777,214 hosts per network. Figure 2 illustrates the structure of class A addresses. Figure 2 Class A IP addresses Class B  Class B addresses are assigned to medium-sized to large-sized networks. The two high-order bits in a class B address are always set to binary 1 0. The next 14 bits (completing the first two octets) complete the network ID. The remaining 16 bits (last two octets) represent the host ID. This allows for16,384 networks and 65,534 hosts per network. Figure 3 illustrates the structure of class B addresses. Figure 3 Class B IP addresses Class C  Class C addresses are used for small networks. The three high-order bits in a class C address a real ways set to binary 1 1 0. The next 21 bits (completing the first three octets) complete the network ID. The remaining 8 bits (last octet) represent the host ID. This allows for 2,097,152 networks and 254hosts per network. Figure 6 illustrates the structure of class C addresses.
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