Research on the various routing tables in Linux system

Linux has a total of 256 0~255 route tables. Where number No. 0 indicates unspec (unspecified), 253,254,255 represents default, main, local table respectively. Tables other than the 4 tables above are reserved for user-specified tables.    Now say the above 5 system table function. The first is table No. 0, unspec. This table can be interpreted as the sum of all routing tables, meaning that all routing entries in the routing table will have a counterpart in the table. That way, if you want to see the routing entries for all the routing tables in the system, you can see this table.    Of course, the route entry operation in this table is also equivalent to the corresponding route entry in other tables, so be careful not to empty the routing table, otherwise all the routing entries will disappear. followed by the main table.    This table is the main routing table, by default, the system adds the route is added to the table inside. The local table, which stores all the local-scoped routing entries, which is the route to the native address.