Стандартный inetd входящий в поставку дистрибутива Slackware нам не подойдет потому, что в нем нельзя указать IP на котором будут слушаться соединения. Заменим inetd на xinetd...

#man inetd
For internet services, the first field of the line may also have a host address specifier prefixed to it, separated from the service name by a colon. If this is done, the string before the colon in the first field indicates what local address inetd should use when listening for that service. Multiple local addresses can be specified on the same line, separated by commas.
--
10.13.0.1:ftp stream tcp nowait root /usr/sbin/tcpd vsftpd /etc/vsftpd/eth0.conf
10.13.1.1:ftp stream tcp nowait root /usr/sbin/tcpd vsftpd /etc/vsftpd/eth1.conf

Q) Help! Does vsftpd do virtual hosting setups?
A1) Yes. If you integrate vsftpd with xinetd, you can use xinetd to bind to
several different IP addresses. For each IP address, get xinetd to launch
vsftpd with a different config file. This way, you can get different behaviour
per virtual address.
A2) Alternatively, run as many copies as vsftpd as necessary, in standalone
mode. Use "listen_address=x.x.x.x" to set the virtual IP.