==== Red Clase A (W.###.###.###) =====
{{:red:tcp_ip:red_a.jpg?600x250|}}
^Mascara ^Bits de Red ^Bits de Host ^Nº máximo de Redes ^Nº máximo de Host ^
|11111111.10000000.00000000.00000000 \\ 255.128.0.0|1|23|2<sup>1</sup>=2|2<sup> 23-2</sup>= 8.388.604|
|11111111.11000000.00000000.00000000 \\ 255.192.0.0|2|22|2<sup>2</sup>=4|2<sup>22-2</sup>=4.194.302|
|11111111.11100000.00000000.00000000 \\ 255.224.0.0|3|21|2<sup>3</sup>=8|2<sup>21-2</sup>=2.097.150|
|11111111.11110000.00000000.00000000 \\ 255.240.0.0|4|20|2<sup>4</sup>=16|2<sup>20-2</sup>=1.048.574|
|11111111.11111000.00000000.00000000 \\ 255.248.0.0|5|19|2<sup>5</sup>=32|2<sup>19-2</sup>=524.286|
|11111111.11111100.00000000.00000000 \\ 255.252.0.0|6|18|2<sup>6</sup>=64|2<sup>18-2</sup>=162.142|
|11111111.11111110.00000000.00000000 \\ 255.254.0.0|7|17|2<sup>7</sup>=128|2<sup>17-2</sup>=131.070|
|11111111.11111111.00000000.00000000 \\ 255.255.0.0|8|16|2<sup>8</sup>=256|2<sup>16-2</sup>=65.534|
|11111111.11111111.10000000.00000000 \\ 255.255.128.0|9|15|2<sup>9</sup>=512|2<sup>15-2</sup>=32.766|
|11111111.11111111.11000000.00000000 \\ 255.255.192.0|10|14|2<sup>10</sup>=1024|2<sup>14-2</sup>=16.382|
|11111111.11111111.11100000.00000000 \\ 255.255.224.0|11|13|2<sup>11</sup>=2048|2<sup>13-2</sup>=8.190|
|11111111.11111111.11110000.00000000 \\ 255.255.240.0|12|12|2<sup>12</sup>=4096|2<sup>12-2</sup>=4094|
|11111111.11111111.11111000.00000000 \\ 255.255.248.0|13|11|2<sup>13</sup>=8192|2<sup>11-2</sup>=2046|
|11111111.11111111.11111100.00000000 \\ 255.255.252.0|14|10|2<sup>14</sup>=16384|2<sup>10-2</sup>=1022|
|11111111.11111111.11111110.00000000 \\ 255.255.254.0|15|9|2<sup>15</sup>=32768|2<sup>9-2</sup>=510|
|11111111.11111111.11111111.00000000 \\ 255.255.255.0|16|8|2<sup>16</sup>=65536|2<sup>8-2</sup>=254|
|11111111.11111111.11111111.10000000 \\ 255.255.255.128|17|7|2<sup>17</sup>=131072|2<sup>7-2</sup>=126|
|11111111.11111111.11111111.11000000 \\ 255.255.255.192|18|6|2<sup>18</sup>=262144|2<sup>6-2</sup>=62|
|11111111.11111111.11111111.11100000 \\ 255.255.255.224|19|5|2<sup>19</sup>=524.288|2<sup>5-2</sup>=30|
|11111111.11111111.11111111.11110000 \\ 255.255.255.240|20|4|2<sup>20</sup>=1048576|2<sup>4-2</sup>=14|
|11111111.11111111.11111111.11111000 \\ 255.255.255.248|21|3|2<sup>21</sup>=2097152|2<sup>3-2</sup>=6|
|11111111.11111111.11111111.11111100 \\ 255.255.255.252|22|12|2<sup>22</sup>=4194304|2<sup>2-2</sup>=2|


<note>Se quitan 2 al nº de hosts debido a que la dirección todo a 1 ó todo a 0 no son válidas ya que están reservadas.</note>
<note important>Está tabla está confeccionada permitiendo el primer bit de subred (RFC 1878) . </note>