Note that you use IP instead of DNS for alternate_names if you're working with an ip address.

As of OpenSSL 1.1.1, providing subjectAltName directly on command line becomes much easier, with the introduction of the -addext flag to openssl req

openssl s_client

This section defines three signature algorithms based on the RSA encryption process described in Sections 8 and 9. The intended use of the signature algorithms is in signing X.509/PEM certificates and certificate-revocation lists, PKCS #6 extended certificates, and other objects employing digital signatures such as X.401 message tokens. The algorithms are not intended for use in constructing digital signatures in PKCS #7. The first signature algorithm (informally, "MD2 with RSA") combines the MD2 message-digest algorithm with RSA, the second (informally, "MD4 with RSA") combines the MD4 message-digest algorithm with RSA, and the third (informally, "MD5 with RSA") combines the MD5 message-digest algorithm with RSA.