PLIP mini-HOWTO:
https://sunsite.unc.edu/LDP/HOWTO/mini/PLIP/
NET-3-HOWTO:
https://sunsite.unc.edu/LDP/HOWTO/NET-3-HOWTO.html
Kernel-HOWTO:
https://sunsite.unc.edu/LDP/HOWTO/Kernel-HOWTO.html
IP Masqerade Resource page:
https://ipmasq.home.ml.org/
ipmasq-HOWTO:
https://www.wiznet.ca/~ambrose/ipmasq-HOWTO.html
ipfwadm:
https://www.xos.nl/linux/ipfwadm/
RFC 1597: ftp://ftp.uoknor.edu/rfc/rfc1597.txt
Firewall-HOWTO:
https://sunsite.unc.edu/LDP/HOWTO/Firewall-HOWTO.html
Network guide: https://linuxwww.db.erau.edu/NAG/