We moved our CIFS/DFS shares to a new storage location this weekend. The address is being shared by 3 domain controllers that then redirects to the primary file share device.

The domain controllers are hosting the namespace but are not hosting any files. They are sending referrals to one primary server rather than load balancing between the two.

The domain is Windows Server 2012 R2 forest and domain functional level. Servers are Windows Server 2012 R2 OS.

Of the 20 servers affected by this change, only 3 refused to mount the CIFS share using the more generic domain controller address.
/var/log/messages:
cifs.upcall: unable to resolve hostname: ZEBRA [Name or service not known]
CIFS VFS: cifs_mount failed w/return code = -6

This is the same entry that is in a dozen other servers and works just fine. /etc/fstab
//domain.local/apps/ESM /esmshare cifs credentials=/etc/creds/creds.cifs,file_mode=0777,dir_mode=0777,uid=200,gid=200,_netdev 0 0

Common threads - all 3 boxes are RHEL 6.9

Here is my request-key.conf config from that box.

OP TYPE DESCRIPTION CALLOUT INFO PROGRAM ARG1 ARG2 ARG3 ...

====== ======= =============== =============== ===============================

create user debug:* negate /bin/keyctl negate %k 30 %S
create user debug:loop:* * |/bin/cat
create user debug:* * /usr/share/keyutils/request-key-debug.sh %k %d %c %S
negate * * * /bin/keyctl negate %k 30 %S
create cifs.spnego * * /usr/sbin/cifs.upcall %k
create dns_resolver * * /usr/sbin/cifs.upcall %k

The request-key binary is in /sbin/ as well as the cifs.upcall being in /usr/sbin.

Thanks.