Transitioning from userland <citerefentry><refentrytitle>natd</refentrytitle><manvolnum>8</manvolnum></citerefentry> to in-kernel <acronym>NAT</acronym> might seem seamless at first but there is small catch. When using the GENERIC kernel, <application>IPFW</application> will load the <filename>libalias.ko</filename> kernel module, when <literal>firewall_nat_enable</literal> is enabled in <filename>rc.conf</filename>. The <filename>libalias.ko</filename> kernel module only provides basic <acronym>NAT</acronym> functionality, whereas the userland implementation <citerefentry><refentrytitle>natd</refentrytitle><manvolnum>8</manvolnum></citerefentry> has all <acronym>NAT</acronym> functionality available in its userland library without any extra configuration. All functionality refers to the following kernel modules that can additionally be loaded when needed besides the standard <filename>libalias.ko</filename> kernel module: <filename>alias_cuseeme.ko</filename>, <filename>alias_ftp.ko</filename>, <filename>alias_bbt.ko</filename>, <filename>skinny.ko</filename>, <filename>irc.ko</filename>, <filename>alias_pptp.ko</filename> and <filename>alias_smedia.ko</filename> using the <literal>kld_list</literal> directive in <filename>rc.conf</filename>. If a custom kernel is used, the full functionality of the userland library can be compiled in, in the kernel, using the <option>options LIBALIAS</option>.
bhy
虽然，加载的<filename>libalias.ko</filename>模块只提供基本的<acronym>NAT</acronym>功能，而 userland 实现<citerefentry><refentrytitle>natd</refentrytitle><manvolnum>8</manvolnum></citerefentry>具有所有可用的功能，而无需从其用户库进行任何额外的配置。所有功能都是指在标准<filename>libalias.ko</filename>内核模块之外，在需要时可以额外加载的以下内核模块：<filename>alias_cuseeme.ko</filename>，<filename>alias_ftp.ko</filename>，<filename>alias_bbt.ko</filename>，<filename>skinny.ko</filename>，<filename>irc.ko</filename>，<filename>alias_pptp.ko</filename>，<filename>alias_smedia.ko</filename>使用<filename>rc.conf</filename>中的 <literal>kld_list</literal>指令来模拟用户实现的全部功能。如果使用自定义内核，则可以使用<option>option LIBALIAS</option>。