DNS client on RAC nodes not resolv SCAN IP from DNS server

 Hi all, I setup RAC two nodes using DSN server for SCAN ip, my pflatform is soalris 11.1 and RAC 11.2.0.4. My config is below, 

1/ At DNS server side config(hostname: coredns)

root@coredns:/srv/named/data# cat /etc/named.conf

options {

directory "/srv/named/data";

};

zone "sample.com" in {

        type master ;

        file "domain.sample.com";

};

zone "in-addr.arpa" in {

        type master ;

        file "rdomain.sample.com";

};

root@coredns:/srv/named/data# cat domain.sample.com

; Forward map for sample.com

$TTL 1h

@               in soa  coredns. root.coredns.sample.com.  (

                         20110925

                         43200                         

                         3600

                         604800

                         86400  )

                 in ns   coredns.

;                in ns   SLAVE.sample.com.

;                in mx 10        mail.sample.com.