It is not clear why smbstatus in the machine name field shows the string "__ffff_"?

Question

linux

There is a domain on Samba v. 3.2.11.
When connecting the share by users under linux (most often under Ubuntu),
in the output of the command smbstatus -p
, the name field of such machines is displayed as follows:
__ffff_
Although the names of win machines are displayed correctly.
Not critical, but I would like to understand ...