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<topic xml:lang="en-us" id="nat-adv-alias">
  <title>Configuring Aliasing of the NAT Engine</title>
  
  <body>
    <p>By default, the NAT core uses aliasing and uses random ports when generating an alias for a connection. This
      works well for the most protocols like SSH, FTP and so on. Though some protocols might need a more transparent
      behavior or may depend on the real port number the packet was sent from. You can change the NAT mode by using the
      following commands: </p>
    <pre xml:space="preserve">$ VBoxManage modifyvm <varname>VM-name</varname> \
--nataliasmode1 proxyonly</pre>
    <pre xml:space="preserve">$ VBoxManage modifyvm "Linux Guest" --nataliasmode1 sameports</pre>
    <p>The first example disables aliasing and switches NAT into transparent mode, the second example enforces
      preserving of port values. These modes can be combined if necessary. </p>
  </body>
  
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