Log in credentials for SMB network drive

Help needed...

every time I start my Mac with macOS Sierra I'm asked to log in my SMB network drive. This is fine, the problem is that my credentials are not saved into keychain.

More details:

The network drive is connected to my Netgear router. The user name set in the router configuration page is "admin" by default and cannot be changed.

The log in screen pops up with the user name "Xxxxxx"what is my Mac user and administrator name. I overwrite the "Xxxxxx" into "admin" then write

the password, tick the box "Remember this password in my keychain" and log in. It is working fine, but the credentials are not stored to keychain.

At restart everything goes from the beginning. I also changed in keychain the user name for this login item but without any effect on procedure.

Any idea how to solve this?

Thank you