Route cloning

Route cloning allows a host route to be created for every host that a system communicates with.

When network traffic is about to be sent, a search is done of the routing table to find a route to that host. If a specific host route is found, it will be used. If a specific host route is not found, a network route or the default route may be found. If the route that is found has the cloning flag, 'c', set, a host route for the destination will be created using the gateway from the route that is being cloned. Subsequent routing table searches for that destination will find the cloned host route. Cloned routes have the 'W' flag set. These routes will time out and be deleted from the routing table if they are unused for route_expire minutes. You can modify route_expire by using the no command.

The route cloning feature is used mainly by the path MTU discovery protocol within AIX operating system, to allow it to keep track of path MTU information for every destination it communicates with. If the network options tcp_pmtu_discover or udp_pmtu_discover (settable with the no command) are 1, the cloning flag is turned on for all network routes on the system. The path MTU discovery protocol is on by default.