rule/table routing intro https://blog.scottlowe.org/2013/05/29/a-quick-introduction-to-linux-policy-routing/
Routingpacket | | routing-policy | | \ / ` routing-table
The routing policy is managed by iproute2.
routing tables determine what network a packets is sent to.
A variety of tools can be used to manage it, but iproute2 is generally used today.
Prior to iproute2, net-tools route was generally used to manage the routing table in Linux.
You can also dump the routing table with netstat -r.
Both iptables and more recently nftables are builtin to the linux kernel to manage rules.
There are also various abstractions overtop of them.