Thanks a lot Tim. So as I understand the configuration for SSL with Basic license, those settings are also required since server aren't able to reach each other.
xpack.security.enabled: true
xpack.security.transport.ssl.enabled: true
xpack.security.transport.ssl.verification_mode: certificate
xpack.security.transport.ssl.keystore.path: certificates.p12
xpack.security.transport.ssl.truststore.path: certificates.p12