both ipv4 and ipv6 of shorewall is needed installed on soekris, recommend a small harddisk, not a small cfcard, use the cfcard for install image on the harddisk, not reversed, i recommend the gentoo as router distro, if you get one of the gigabit soekris then you are more then ever ready to power fidonet :)
if no cfcard, then boot sysresquecd and start the pxe server on it, now boot the soekris via pxe