Briefly describe the IP layer lookup routing algorithm of the Internet in the case of using subnet masks

The header of the datagram received by the person extracts the destination Internet Protocol Address D.
First determine whether it is a direct delivery. Check the networks directly connected to the router one by one: use the subnet mask and D of each network to “AND” bit by bit to see if the result matches the corresponding network address. If it matches, the packet is directly delivered (of course, D needs to be converted into a physical address, and the datagram is packaged into a frame and sent out), and the forwarding task is over. Otherwise, it is an indirect delivery, execute (3)
Indirect delivery: If there is a specific host route with destination address D in the routing table, the datagram is sent to the next-hop router specified in the routing table, otherwise
Execute (4). There is no specific host route with destination address D in the general routing table: for each row in the routing table (destination network address, subnet mask, next hop address), use the subnet mask and D in it bit-by-bit “AND” (AND operation), the result is N. If N matches the destination network address of the row, the datagram is sent to the next hop router indicated at the beginning of the row; otherwise, execute (5)
No default route: If there is a default route in the routing table, send the datagram to the default route specified in the routing table; otherwise, execute (6).
Report a forwarding packet error.