ipr_redirect(port_nr, dest, netmask, old_gateway, new_gateway, timeout) attempts to find a route for the destination dest, ipr_redirect()'s second parameter, in the output routing table. If a dynamic route whose gateway is old_gateway (ipr_redirect()'s fourth parameter) is found, this route is marked as unreachable and a new route with values of port_nr, dest, netmask, new_gateway, and timeout is added to the output routing table.