[Koha] How I can config the Memcached tab

Hello everyone I try to have the Server without error or warnings and I want to fix the memcached tab. Memcached: Servers: undefined | Namespace: undefined | Status: unknown | Config read from: Nowhere Note that the right place to define the memcached config is in your $KOHA_CONF file. Currently you do not have a valid memcached configuration defined. | Effective caching method: Cache::Memory How I can fix this warning or what are the default config? Server: Debian 9.3 Koha version: 17.11.02.000 Thank you!