The current configuration file is A, upload the new configuration file B through FTP/SFTP to the NE router, there are three methods to load the configuration in another configuration file:
1) The command "load configuration file B merge", it merges A with B, no need reboot.
2) The command "startup system-software B all" needs reboot then the new configuration B can be loaded, without merge.
3) The command "rollback configuration to file B", this command replaces the current configuration with the new configuration, without any merge or reboot to the router.