Connect NAS via WebDAV to NextCloud with local ip adress: 192.168.XX.XX

I have 2 computers. First is Ubuntu 18.04 with NextCloud and it`s work fine. Second is my NAS storage QNAP. I want to connect my NAS with local ip to my NextCloud. For example:

NextCloud have ip -
QNAP have ip -

I use External Storage plugin, and if I connect my WebDAV with its work fine, but very slow. I want to connect with local ip of my NAS -> NextCloud doesn't want to understand the local ip. I check the connection with other program and its work fine. I think if I will use the local ip it will be more faster.

Why I want to do like this? I have a lot of clients, and I want them to connect to the externa storage with their logins.