zone db.net/IN: NS 'centos610server.db.net' has no address records (A or AAAA)

hi to all, I've centso6.10 i upgraged due to last problem ( reverse zone is not working ). but now in forward zone following error has occured:-
Code:[root@centos610server named]# service named restart
Stopping named: [ OK ]
Starting named:
Error in named configuration:
zone localhost.localdomain/IN: loaded serial 0
zone localhost/IN: loaded serial 0
zone 1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.ip6.arpa/IN: loaded serial 0
zone 1.0.0.127.in-addr.arpa/IN: loaded serial 0
zone 0.in-addr.arpa/IN: loaded serial 0
zone 20.168.192.in-addr.arpa/IN: loaded serial 10
zone db.net/IN: NS 'centos610server.db.net' has no address records (A or AAAA)
zone db.net/IN: not loaded due to errors.
_default/db.net/IN: bad zonemine forward zone file is :-
Code:$TTL 1D
@ IN SOA db.net. root.db.net. (
10 ; serial
1D ; refresh
1H ; retry
1W ; expire
3H ) ; minimum
@ IN NS centos610server.db.net.
centos610server IN A 192.168.20.3
centos610oraserver IN A 192.168.20.5and reverse zone file is :-
Code:$TTL 1D
@ IN SOA db.net. root.db.net. (
10 ; serial
1D ; refresh
1H ; retry
1W ; expire
3H ) ; minimum
@ IN NS centos610server.db.net.
3 IN PTR centos610server.db.net.
5 IN PTR centos610oraserver.db.net.how to resolve it.