If you want to learn more about using Linux as a router, there are some helpful resources and references that you can consult. For example, the manual page for the ip command (man ip) is used to manipulate IP addresses, routing tables, and other network settings. Additionally, the manual page for the iptables command (man iptables) is used to configure the firewall rules and NAT on Linux. The manual page for the dhcpd command (man dhcpd) is used to run the DHCP server on Linux, while man named is used to run the DNS server. The ping command (man ping) tests the network connectivity and latency between two hosts, while traceroute (man traceroute) traces the route and hops that a packet takes from one host to another. Furthermore, tcpdump (man tcpdump) captures and analyzes network packets on Linux, and netstat (man netstat) displays various network statistics and information on Linux. There is also a tutorial that explains how to set up a basic Linux router with Debian or Ubuntu, as well as a guide that covers various aspects and features of using Linux as a router such as firewall, NAT, VPN, QoS, web filtering and more.