[dns-operations] A question about changing nameservers

[Feng He]

Hello,

My platform DNSbed.com has cloudwebdns.com as the nameserver domain.
The DNS of cloudwebdns.com is currently hosted by:
dns1.registrar-servers.com.
dns2.registrar-servers.com.
dns3.registrar-servers.com.
dns4.registrar-servers.com.
dns5.registrar-servers.com.

Today I changed the nameservers to our own nameservers:
ns1.cloudwebdns.com.
ns2.cloudwebdns.com.
ns3.cloudwebdns.com.
ns4.cloudwebdns.com.

I have added the zone to named.conf, created zone files, and reloaded 
BIND. But when I added a record by nsupdate, it got the error:

response to SOA query was unsuccessful

When I dig to localhost:
dig cloudwebdns.com soa @localhost

Got the status ServFail.

Can you tell me what has happened?

Thanks.