dhclient seems to request a username from nslcd with a wildcard "*".
This is denied by nslcd.

Every time dhclient is runs, the following is in syslog:

Dec 23 07:48:50 dhclient[1183]: DHCPREQUEST of 81.16.33.27 on eth0 to 81.16.33.2 port 67
Dec 23 07:48:50 dhclient[1183]: DHCPACK of 81.16.33.27 from 81.16.33.2
Dec 23 07:48:50 nslcd[21573]: [885e1b] DEBUG: connection from pid=504 uid=0 gid=0
Dec 23 07:48:50 nslcd[21573]: [885e1b] <passwd="*"> request denied by validnames option
Dec 23 07:48:50 dhclient[1183]: bound to 81.16.33.27 -- renewal in 1234 seconds.

Dear submitter,

as the package isc-dhcp has just been removed from the Debian archive
unstable we hereby close the associated bug reports.  We are sorry
that we couldn't deal with your issue properly.

For details on the removal, please see https://bugs.debian.org/1143544

The version of this package that was in Debian prior to this removal
can still be found using https://snapshot.debian.org/.

Please note that the changes have been done on the master archive and
will not propagate to any mirrors until the next dinstall run at the
earliest.

This message was generated automatically; if you believe that there is
a problem with it please contact the archive administrators by mailing
ftpmaster@ftp-master.debian.org.

Debian distribution maintenance software
pp.
Thorsten Alteholz (the ftpmaster behind the curtain)