resolver problem at boot

[grocanar]

Hi

I m using CentOS Linux release 7.5.1804 (Core)

and i have the following problem
my fstab contain

snap-n02.genoscope.cns.fr:/dbbackup /env/export/dbbackup nfs rw,intr,hard,nodev,nosuid,noacl,vers=3,_netdev,timeo=14 0 0
cns-labgem-n05.genoscope.cns.fr:/cns_labgem_n05 /env/export/cns_labgem_n05 nfs rw,intr,hard,nodev,nosuid,noacl,vers=3,_netdev,comment=systemd.automount,timeo=14 0 0
cns-home.genoscope.cns.fr:/vol/home /env/export/home nfs rw,nosuid,nodev,intr,hard,noacl,nfsvers=3,_netdev,comment=systemd.automount,timeo=14 0 0

but at boot the nfs share is not mounted

after boot if i ran mount -a the share are mounted without problem

in the journal log i got
août 30 17:21:24 eyjafjoll.genoscope.cns.fr mount[1656]: mount.nfs: Failed to resolve server snap-n02.genoscope.cns.fr: Name or service not known
août 30 17:21:24 eyjafjoll.genoscope.cns.fr mount[1664]: mount.nfs: Failed to resolve server cns-labgem-n05.genoscope.cns.fr: Name or service not known

i have put the ip of cns-home.genoscope.cns.fr in /etc/hosts and then the nfs share is mounted during the boot process

then it seems that is only the resolver that does'nt work

but the network is already up

août 30 17:20:49 eyjafjoll.genoscope.cns.fr kernel: bond0: Enslaving em2 as a backup interface with an up link
août 30 17:20:49 eyjafjoll.genoscope.cns.fr systemd-networkd[1332]: bond0 : gained carrier
août 30 17:20:49 eyjafjoll.genoscope.cns.fr kernel: bond0: Warning: No 802.3ad response from the link partner for any adapters in the bond
août 30 17:20:49 eyjafjoll.genoscope.cns.fr kernel: IPv6: ADDRCONF(NETDEV_UP): bond0: link is not ready
août 30 17:20:49 eyjafjoll.genoscope.cns.fr kernel: IPv6: ADDRCONF(NETDEV_CHANGE): bond0: link becomes ready
août 30 17:20:49 eyjafjoll.genoscope.cns.fr kernel: bond0: link status definitely up for interface em1, 10000 Mbps full duplex
août 30 17:20:49 eyjafjoll.genoscope.cns.fr kernel: bond0: first active interface up!
août 30 17:20:49 eyjafjoll.genoscope.cns.fr kernel: bond0: link status definitely up for interface em2, 10000 Mbps full duplex
août 30 17:20:54 eyjafjoll.genoscope.cns.fr network[1265]: Activation de l'interface bond0 : [ OK ]

août 30 17:20:54 eyjafjoll.genoscope.cns.fr systemd[1]: Reached target Network is Online.
août 30 17:20:54 eyjafjoll.genoscope.cns.fr systemd[1]: Starting Network is Online.
août 30 17:20:54 eyjafjoll.genoscope.cns.fr systemd[1]: Mounting /env/export/dbbackup...

i m really puzzled by this problem

does soemeone already seen the problem?