IPv4サブネットマスクの検討

ネットワーク設計、ルータやファイアウォールの定義設定時などでご利用くださいませ。

#ルータマニュアル
- CISCO [ルータ](https://www.cisco.com/c/ja_jp/td.html)
- YAMAHA [RTシリーズ](http://www.rtpro.yamaha.co.jp/RT/manual.html)

#範囲
※サブネットを示す場合、ノードとして利用できる個数は -2。

<table>
<tr><th width=50>個数※</th><th width=50>bitmask</th><th width=50>subnet<br>mask</th><th>range(s)</th></tr>
<tr><th>1</th><th>/32</th><td>255</td><td>(省略)</td></tr>
<tr><th>2</th><th>/31</th><td>254</td><td>0-1, 2-3, 4-5, 6-7, 8-9, 10-11, .... , 252-253, 254-255</td></tr>
<tr><th>4</th><th>/30</th><td>252</td><td>0-3,4-7,8-11,12-15,16-19,20-23,24-27,28-31,32-35,36-39,40-43,44-47,48-51,52-55,56-59,60-63,64-67,68-71,72-75,76-79,80-83,84-87,88-91,92-95,96-99,<br><br>100-103,104-107,108-111,112-115,116-119,120-123,124-127,128-131,132-135,136-139,140-143,144-147,148-151,152-155,156-159,160-163,164-167,168-171,172-175,176-179,180-183,184-187,188-191,192-195,196-199,<br><br>200-203,204-207,208-211,212-215,216-219,220-223,224-227,228-231,232-235,236-239,240-243,244-247,248-251,252-255</td></tr>
<tr><th>8</th><th>/29</th><td>248</td><td>0-7,8-15,16-23,24-31,32-39,40-47,48-55,56-63,64-71,72-79,80-87,88-95,96-103,<br><br>104-111,112-119,120-127,128-135,136-143,144-151,152-159,160-167,168-175,176-183,184-191,192-199,<br><br>200-207,208-215,216-223,224-231,232-239,240-247,248-255</td></tr>
<tr><th>16</th><th>/28</th><td>240</td><td>0-15,16-31,32-47,48-63,64-79,80-95,96-111,<br><br>112-127,128-143,144-159,160-175,176-191,192-207,<br><br>208-223,224-239,240-255</td></tr>
<tr><th>32</th><th>/27</th><td>224</td><td>0-31,32-63,64-95,96-127,128-159,160-191,192-223,224-255</td></tr>
<tr><th>64</th><th>/26</th><td>192</td><td>0-63,64-127,128-191,192-255</td></tr>
<tr><th>128</th><th>/25</th><td>128</td><td>0-127,128-255</td></tr>
<tr><th>256</th><th>/24</th><td>0</td><td>0-255</td></tr>
</table>


#テーブル
※サブネットを示す場合、ノードとして利用できる個数は -2。

<table>
<tr><th>個数※</th><th>1</th><th>2</th><th>4</th><th>8</th><th>16</th><th>32</th><th>64</th><th>128</th><th>256</th></tr>
<tr><th>subnetmask</th><th>255</th><th>254</th><th>252</th><th>248</th><th>240</th><th>224</th><th>192</th><th>128</th><th>0</th></tr>
<tr><th>bitmask</th><th>/32</th><th>/31</th><th>/30</th><th>/29</th><th>/28</th><th>/27</th><th>/26</th><th>/25</th><th>/24</th></tr>
<tr><th>0</th><td>0</td><td rowspan=2>0</td><td rowspan=4>0</td><td rowspan=8>0</td><td rowspan=16>0</td><td rowspan=32>0</td><td rowspan=64>0</td><td rowspan=128>0</td><td rowspan=256>0</td></tr>
<tr><th>1</th><td>1</td></tr>
<tr><th>2</th><td>2</td><td rowspan=2>2</td></tr>
<tr><th>3</th><td>3</td></tr>
<tr><th>4</th><td>4</td><td rowspan=2>4</td><td rowspan=4>4</td></tr>
<tr><th>5</th><td>5</td></tr>
<tr><th>6</th><td>6</td><td rowspan=2>6</td></tr>
<tr><th>7</th><td>7</td></tr>
<tr><th>8</th><td>8</td><td rowspan=2>8</td><td rowspan=4>8</td><td rowspan=8>8</td></tr>
<tr><th>9</th><td>9</td></tr>
<tr><th>10</th><td>10</td><td rowspan=2>10</td></tr>
<tr><th>11</th><td>11</td></tr>
<tr><th>12</th><td>12</td><td rowspan=2>12</td><td rowspan=4>12</td></tr>
<tr><th>13</th><td>13</td></tr>
<tr><th>14</th><td>14</td><td rowspan=2>14</td></tr>
<tr><th>15</th><td>15</td></tr>
<tr><th>16</th><td>16</td><td rowspan=2>16</td><td rowspan=4>16</td><td rowspan=8>16</td><td rowspan=16>16</td></tr>
<tr><th>17</th><td>17</td></tr>
<tr><th>18</th><td>18</td><td rowspan=2>18</td></tr>
<tr><th>19</th><td>19</td></tr>
<tr><th>20</th><td>20</td><td rowspan=2>20</td><td rowspan=4>20</td></tr>
<tr><th>21</th><td>21</td></tr>
<tr><th>22</th><td>22</td><td rowspan=2>22</td></tr>
<tr><th>23</th><td>23</td></tr>
<tr><th>24</th><td>24</td><td rowspan=2>24</td><td rowspan=4>24</td><td rowspan=8>24</td></tr>
<tr><th>25</th><td>25</td></tr>
<tr><th>26</th><td>26</td><td rowspan=2>26</td></tr>
<tr><th>27</th><td>27</td></tr>
<tr><th>28</th><td>28</td><td rowspan=2>28</td><td rowspan=4>28</td></tr>
<tr><th>29</th><td>29</td></tr>
<tr><th>30</th><td>30</td><td rowspan=2>30</td></tr>
<tr><th>31</th><td>31</td></tr>
<tr><th>32</th><td>32</td><td rowspan=2>32</td><td rowspan=4>32</td><td rowspan=8>32</td><td rowspan=16>32</td><td rowspan=32>32</td></tr>
<tr><th>33</th><td>33</td></tr>
<tr><th>34</th><td>34</td><td rowspan=2>34</td></tr>
<tr><th>35</th><td>35</td></tr>
<tr><th>36</th><td>36</td><td rowspan=2>36</td><td rowspan=4>36</td></tr>
<tr><th>37</th><td>37</td></tr>
<tr><th>38</th><td>38</td><td rowspan=2>38</td></tr>
<tr><th>39</th><td>39</td></tr>
<tr><th>40</th><td>40</td><td rowspan=2>40</td><td rowspan=4>40</td><td rowspan=8>40</td></tr>
<tr><th>41</th><td>41</td></tr>
<tr><th>42</th><td>42</td><td rowspan=2>42</td></tr>
<tr><th>43</th><td>43</td></tr>
<tr><th>44</th><td>44</td><td rowspan=2>44</td><td rowspan=4>44</td></tr>
<tr><th>45</th><td>45</td></tr>
<tr><th>46</th><td>46</td><td rowspan=2>46</td></tr>
<tr><th>47</th><td>47</td></tr>
<tr><th>48</th><td>48</td><td rowspan=2>48</td><td rowspan=4>48</td><td rowspan=8>48</td><td rowspan=16>48</td></tr>
<tr><th>49</th><td>49</td></tr>
<tr><th>50</th><td>50</td><td rowspan=2>50</td></tr>
<tr><th>51</th><td>51</td></tr>
<tr><th>52</th><td>52</td><td rowspan=2>52</td><td rowspan=4>52</td></tr>
<tr><th>53</th><td>53</td></tr>
<tr><th>54</th><td>54</td><td rowspan=2>54</td></tr>
<tr><th>55</th><td>55</td></tr>
<tr><th>56</th><td>56</td><td rowspan=2>56</td><td rowspan=4>56</td><td rowspan=8>56</td></tr>
<tr><th>57</th><td>57</td></tr>
<tr><th>58</th><td>58</td><td rowspan=2>58</td></tr>
<tr><th>59</th><td>59</td></tr>
<tr><th>60</th><td>60</td><td rowspan=2>60</td><td rowspan=4>60</td></tr>
<tr><th>61</th><td>61</td></tr>
<tr><th>62</th><td>62</td><td rowspan=2>62</td></tr>
<tr><th>63</th><td>63</td></tr>
<tr><th>64</th><td>64</td><td rowspan=2>64</td><td rowspan=4>64</td><td rowspan=8>64</td><td rowspan=16>64</td><td rowspan=32>64</td><td rowspan=64>64</td></tr>
<tr><th>65</th><td>65</td></tr>
<tr><th>66</th><td>66</td><td rowspan=2>66</td></tr>
<tr><th>67</th><td>67</td></tr>
<tr><th>68</th><td>68</td><td rowspan=2>68</td><td rowspan=4>68</td></tr>
<tr><th>69</th><td>69</td></tr>
<tr><th>70</th><td>70</td><td rowspan=2>70</td></tr>
<tr><th>71</th><td>71</td></tr>
<tr><th>72</th><td>72</td><td rowspan=2>72</td><td rowspan=4>72</td><td rowspan=8>72</td></tr>
<tr><th>73</th><td>73</td></tr>
<tr><th>74</th><td>74</td><td rowspan=2>74</td></tr>
<tr><th>75</th><td>75</td></tr>
<tr><th>76</th><td>76</td><td rowspan=2>76</td><td rowspan=4>76</td></tr>
<tr><th>77</th><td>77</td></tr>
<tr><th>78</th><td>78</td><td rowspan=2>78</td></tr>
<tr><th>79</th><td>79</td></tr>
<tr><th>80</th><td>80</td><td rowspan=2>80</td><td rowspan=4>80</td><td rowspan=8>80</td><td rowspan=16>80</td></tr>
<tr><th>81</th><td>81</td></tr>
<tr><th>82</th><td>82</td><td rowspan=2>82</td></tr>
<tr><th>83</th><td>83</td></tr>
<tr><th>84</th><td>84</td><td rowspan=2>84</td><td rowspan=4>84</td></tr>
<tr><th>85</th><td>85</td></tr>
<tr><th>86</th><td>86</td><td rowspan=2>86</td></tr>
<tr><th>87</th><td>87</td></tr>
<tr><th>88</th><td>88</td><td rowspan=2>88</td><td rowspan=4>88</td><td rowspan=8>88</td></tr>
<tr><th>89</th><td>89</td></tr>
<tr><th>90</th><td>90</td><td rowspan=2>90</td></tr>
<tr><th>91</th><td>91</td></tr>
<tr><th>92</th><td>92</td><td rowspan=2>92</td><td rowspan=4>92</td></tr>
<tr><th>93</th><td>93</td></tr>
<tr><th>94</th><td>94</td><td rowspan=2>94</td></tr>
<tr><th>95</th><td>95</td></tr>
<tr><th>96</th><td>96</td><td rowspan=2>96</td><td rowspan=4>96</td><td rowspan=8>96</td><td rowspan=16>96</td><td rowspan=32>96</td></tr>
<tr><th>97</th><td>97</td></tr>
<tr><th>98</th><td>98</td><td rowspan=2>98</td></tr>
<tr><th>99</th><td>99</td></tr>
<tr><th>100</th><td>100</td><td rowspan=2>100</td><td rowspan=4>100</td></tr>
<tr><th>101</th><td>101</td></tr>
<tr><th>102</th><td>102</td><td rowspan=2>102</td></tr>
<tr><th>103</th><td>103</td></tr>
<tr><th>104</th><td>104</td><td rowspan=2>104</td><td rowspan=4>104</td><td rowspan=8>104</td></tr>
<tr><th>105</th><td>105</td></tr>
<tr><th>106</th><td>106</td><td rowspan=2>106</td></tr>
<tr><th>107</th><td>107</td></tr>
<tr><th>108</th><td>108</td><td rowspan=2>108</td><td rowspan=4>108</td></tr>
<tr><th>109</th><td>109</td></tr>
<tr><th>110</th><td>110</td><td rowspan=2>110</td></tr>
<tr><th>111</th><td>111</td></tr>
<tr><th>112</th><td>112</td><td rowspan=2>112</td><td rowspan=4>112</td><td rowspan=8>112</td><td rowspan=16>112</td></tr>
<tr><th>113</th><td>113</td></tr>
<tr><th>114</th><td>114</td><td rowspan=2>114</td></tr>
<tr><th>115</th><td>115</td></tr>
<tr><th>116</th><td>116</td><td rowspan=2>116</td><td rowspan=4>116</td></tr>
<tr><th>117</th><td>117</td></tr>
<tr><th>118</th><td>118</td><td rowspan=2>118</td></tr>
<tr><th>119</th><td>119</td></tr>
<tr><th>120</th><td>120</td><td rowspan=2>120</td><td rowspan=4>120</td><td rowspan=8>120</td></tr>
<tr><th>121</th><td>121</td></tr>
<tr><th>122</th><td>122</td><td rowspan=2>122</td></tr>
<tr><th>123</th><td>123</td></tr>
<tr><th>124</th><td>124</td><td rowspan=2>124</td><td rowspan=4>124</td></tr>
<tr><th>125</th><td>125</td></tr>
<tr><th>126</th><td>126</td><td rowspan=2>126</td></tr>
<tr><th>127</th><td>127</td></tr>
<tr><th>128</th><td>128</td><td rowspan=2>128</td><td rowspan=4>128</td><td rowspan=8>128</td><td rowspan=16>128</td><td rowspan=32>128</td><td rowspan=64>128</td><td rowspan=128>128</td></tr>
<tr><th>129</th><td>129</td></tr>
<tr><th>130</th><td>130</td><td rowspan=2>130</td></tr>
<tr><th>131</th><td>131</td></tr>
<tr><th>132</th><td>132</td><td rowspan=2>132</td><td rowspan=4>132</td></tr>
<tr><th>133</th><td>133</td></tr>
<tr><th>134</th><td>134</td><td rowspan=2>134</td></tr>
<tr><th>135</th><td>135</td></tr>
<tr><th>136</th><td>136</td><td rowspan=2>136</td><td rowspan=4>136</td><td rowspan=8>136</td></tr>
<tr><th>137</th><td>137</td></tr>
<tr><th>138</th><td>138</td><td rowspan=2>138</td></tr>
<tr><th>139</th><td>139</td></tr>
<tr><th>140</th><td>140</td><td rowspan=2>140</td><td rowspan=4>140</td></tr>
<tr><th>141</th><td>141</td></tr>
<tr><th>142</th><td>142</td><td rowspan=2>142</td></tr>
<tr><th>143</th><td>143</td></tr>
<tr><th>144</th><td>144</td><td rowspan=2>144</td><td rowspan=4>144</td><td rowspan=8>144</td><td rowspan=16>144</td></tr>
<tr><th>145</th><td>145</td></tr>
<tr><th>146</th><td>146</td><td rowspan=2>146</td></tr>
<tr><th>147</th><td>147</td></tr>
<tr><th>148</th><td>148</td><td rowspan=2>148</td><td rowspan=4>148</td></tr>
<tr><th>149</th><td>149</td></tr>
<tr><th>150</th><td>150</td><td rowspan=2>150</td></tr>
<tr><th>151</th><td>151</td></tr>
<tr><th>152</th><td>152</td><td rowspan=2>152</td><td rowspan=4>152</td><td rowspan=8>152</td></tr>
<tr><th>153</th><td>153</td></tr>
<tr><th>154</th><td>154</td><td rowspan=2>154</td></tr>
<tr><th>155</th><td>155</td></tr>
<tr><th>156</th><td>156</td><td rowspan=2>156</td><td rowspan=4>156</td></tr>
<tr><th>157</th><td>157</td></tr>
<tr><th>158</th><td>158</td><td rowspan=2>158</td></tr>
<tr><th>159</th><td>159</td></tr>
<tr><th>160</th><td>160</td><td rowspan=2>160</td><td rowspan=4>160</td><td rowspan=8>160</td><td rowspan=16>160</td><td rowspan=32>160</td></tr>
<tr><th>161</th><td>161</td></tr>
<tr><th>162</th><td>162</td><td rowspan=2>162</td></tr>
<tr><th>163</th><td>163</td></tr>
<tr><th>164</th><td>164</td><td rowspan=2>164</td><td rowspan=4>164</td></tr>
<tr><th>165</th><td>165</td></tr>
<tr><th>166</th><td>166</td><td rowspan=2>166</td></tr>
<tr><th>167</th><td>167</td></tr>
<tr><th>168</th><td>168</td><td rowspan=2>168</td><td rowspan=4>168</td><td rowspan=8>168</td></tr>
<tr><th>169</th><td>169</td></tr>
<tr><th>170</th><td>170</td><td rowspan=2>170</td></tr>
<tr><th>171</th><td>171</td></tr>
<tr><th>172</th><td>172</td><td rowspan=2>172</td><td rowspan=4>172</td></tr>
<tr><th>173</th><td>173</td></tr>
<tr><th>174</th><td>174</td><td rowspan=2>174</td></tr>
<tr><th>175</th><td>175</td></tr>
<tr><th>176</th><td>176</td><td rowspan=2>176</td><td rowspan=4>176</td><td rowspan=8>176</td><td rowspan=16>176</td></tr>
<tr><th>177</th><td>177</td></tr>
<tr><th>178</th><td>178</td><td rowspan=2>178</td></tr>
<tr><th>179</th><td>179</td></tr>
<tr><th>180</th><td>180</td><td rowspan=2>180</td><td rowspan=4>180</td></tr>
<tr><th>181</th><td>181</td></tr>
<tr><th>182</th><td>182</td><td rowspan=2>182</td></tr>
<tr><th>183</th><td>183</td></tr>
<tr><th>184</th><td>184</td><td rowspan=2>184</td><td rowspan=4>184</td><td rowspan=8>184</td></tr>
<tr><th>185</th><td>185</td></tr>
<tr><th>186</th><td>186</td><td rowspan=2>186</td></tr>
<tr><th>187</th><td>187</td></tr>
<tr><th>188</th><td>188</td><td rowspan=2>188</td><td rowspan=4>188</td></tr>
<tr><th>189</th><td>189</td></tr>
<tr><th>190</th><td>190</td><td rowspan=2>190</td></tr>
<tr><th>191</th><td>191</td></tr>
<tr><th>192</th><td>192</td><td rowspan=2>192</td><td rowspan=4>192</td><td rowspan=8>192</td><td rowspan=16>192</td><td rowspan=32>192</td><td rowspan=64>192</td></tr>
<tr><th>193</th><td>193</td></tr>
<tr><th>194</th><td>194</td><td rowspan=2>194</td></tr>
<tr><th>195</th><td>195</td></tr>
<tr><th>196</th><td>196</td><td rowspan=2>196</td><td rowspan=4>196</td></tr>
<tr><th>197</th><td>197</td></tr>
<tr><th>198</th><td>198</td><td rowspan=2>198</td></tr>
<tr><th>199</th><td>199</td></tr>
<tr><th>200</th><td>200</td><td rowspan=2>200</td><td rowspan=4>200</td><td rowspan=8>200</td></tr>
<tr><th>201</th><td>201</td></tr>
<tr><th>202</th><td>202</td><td rowspan=2>202</td></tr>
<tr><th>203</th><td>203</td></tr>
<tr><th>204</th><td>204</td><td rowspan=2>204</td><td rowspan=4>204</td></tr>
<tr><th>205</th><td>205</td></tr>
<tr><th>206</th><td>206</td><td rowspan=2>206</td></tr>
<tr><th>207</th><td>207</td></tr>
<tr><th>208</th><td>208</td><td rowspan=2>208</td><td rowspan=4>208</td><td rowspan=8>208</td><td rowspan=16>208</td></tr>
<tr><th>209</th><td>209</td></tr>
<tr><th>210</th><td>210</td><td rowspan=2>210</td></tr>
<tr><th>211</th><td>211</td></tr>
<tr><th>212</th><td>212</td><td rowspan=2>212</td><td rowspan=4>212</td></tr>
<tr><th>213</th><td>213</td></tr>
<tr><th>214</th><td>214</td><td rowspan=2>214</td></tr>
<tr><th>215</th><td>215</td></tr>
<tr><th>216</th><td>216</td><td rowspan=2>216</td><td rowspan=4>216</td><td rowspan=8>216</td></tr>
<tr><th>217</th><td>217</td></tr>
<tr><th>218</th><td>218</td><td rowspan=2>218</td></tr>
<tr><th>219</th><td>219</td></tr>
<tr><th>220</th><td>220</td><td rowspan=2>220</td><td rowspan=4>220</td></tr>
<tr><th>221</th><td>221</td></tr>
<tr><th>222</th><td>222</td><td rowspan=2>222</td></tr>
<tr><th>223</th><td>223</td></tr>
<tr><th>224</th><td>224</td><td rowspan=2>224</td><td rowspan=4>224</td><td rowspan=8>224</td><td rowspan=16>224</td><td rowspan=32>224</td></tr>
<tr><th>225</th><td>225</td></tr>
<tr><th>226</th><td>226</td><td rowspan=2>226</td></tr>
<tr><th>227</th><td>227</td></tr>
<tr><th>228</th><td>228</td><td rowspan=2>228</td><td rowspan=4>228</td></tr>
<tr><th>229</th><td>229</td></tr>
<tr><th>230</th><td>230</td><td rowspan=2>230</td></tr>
<tr><th>231</th><td>231</td></tr>
<tr><th>232</th><td>232</td><td rowspan=2>232</td><td rowspan=4>232</td><td rowspan=8>232</td></tr>
<tr><th>233</th><td>233</td></tr>
<tr><th>234</th><td>234</td><td rowspan=2>234</td></tr>
<tr><th>235</th><td>235</td></tr>
<tr><th>236</th><td>236</td><td rowspan=2>236</td><td rowspan=4>236</td></tr>
<tr><th>237</th><td>237</td></tr>
<tr><th>238</th><td>238</td><td rowspan=2>238</td></tr>
<tr><th>239</th><td>239</td></tr>
<tr><th>240</th><td>240</td><td rowspan=2>240</td><td rowspan=4>240</td><td rowspan=8>240</td><td rowspan=16>240</td></tr>
<tr><th>241</th><td>241</td></tr>
<tr><th>242</th><td>242</td><td rowspan=2>242</td></tr>
<tr><th>243</th><td>243</td></tr>
<tr><th>244</th><td>244</td><td rowspan=2>244</td><td rowspan=4>244</td></tr>
<tr><th>245</th><td>245</td></tr>
<tr><th>246</th><td>246</td><td rowspan=2>246</td></tr>
<tr><th>247</th><td>247</td></tr>
<tr><th>248</th><td>248</td><td rowspan=2>248</td><td rowspan=4>248</td><td rowspan=8>248</td></tr>
<tr><th>249</th><td>249</td></tr>
<tr><th>250</th><td>250</td><td rowspan=2>250</td></tr>
<tr><th>251</th><td>251</td></tr>
<tr><th>252</th><td>252</td><td rowspan=2>252</td><td rowspan=4>252</td></tr>
<tr><th>253</th><td>253</td></tr>
<tr><th>254</th><td>254</td><td rowspan=2>254</td></tr>
<tr><th>255</th><td>255</td></tr>
</table>