Getting this?

root@g73sw01:~# mount -t cifs -o credentials=/home/unbeknownst/.smbcredentials,vers=3.0 //nfs-c01.nix.mds.xyz/nfs-bob ./test -vv
mount: /root/test: mount(2) system call failed: No route to host.
root@g73sw01:~#

Solve it with:

root@g73sw01:~# apt-get install keyutils cifs-utils

Next hurdle, was the following:

tom@g73sw01:~$ id
uid=1000(tom) gid=1000(tom) groups=1000(tom),4(adm),24(cdrom),27(sudo),30(dip),46(plugdev),122(lpadmin),135(lxd),136(sambashare)
tom@g73sw01:~$ mount -t cifs -o credentials=$(pwd)/.smbcredentials,vers=3.0,uid=1000,gid=1000 //nfs-c01.nix.mds.xyz/nfs-vincent ./samba
mount.cifs: permission denied: no match for /home/tom/samba found in /etc/fstab
tom@g73sw01:~$

Strangely enough, the solution for this one is NOT to use mount -t cifs , but mount.cifs:

tom@g73sw01:~$ sudo mount.cifs //nfs-c01.nix.mds.xyz/nfs-vincent /home/tom/samba -o credentials=$(pwd)/.smbcredentials,vers=3.0,uid=1000,gid=1000
[sudo] password for tom:
tom@g73sw01:~$

Testing this out a bit further, reveals the mount needs to be done via sudo:

tom@g73sw01:~$ mount -t cifs //nfs-c01.nix.mds.xyz/nfs-vincent ./samba -o credentials=$(pwd)/.smbcredentials,vers=3.0,uid=1000,gid=1000
mount.cifs: permission denied: no match for /home/tom/samba found in /etc/fstab
tom@g73sw01:~$ mount.cifs //nfs-c01.nix.mds.xyz/nfs-vincent ./samba -o credentials=$(pwd)/.smbcredentials,vers=3.0,uid=1000,gid=1000
mount.cifs: permission denied: no match for /home/tom/samba found in /etc/fstab
tom@g73sw01:~$ sudo mount -t cifs //nfs-c01.nix.mds.xyz/nfs-vincent ./samba -o credentials=$(pwd)/.smbcredentials,vers=3.0,uid=1000,gid=1000
tom@g73sw01:~$

Not the best error message to indicate the real reason for the mount failure.  Testing from another user, reveals access denied:

[tom@mds.xyz@g73sw01:~] :([U]$ pwd
/n/mds.xyz/tom
[tom@mds.xyz@g73sw01:~] :)[U]$ cd /home/tom/samba
bash: cd: /home/tom/samba: Permission denied
[tom@mds.xyz@g73sw01:~] :([U]$

Perfect!

Cheers,
HTH