moving dns table

[avsaf]

hi i need your help ,
we have 3 domains a,b,c
a was our primary domain
b was alias to a and contains the dns table : ns1.b.com , ns2.b.com
c was alias to a

now we want c to be our primary domain the steps we done was :

redirect 301 from a to c

but now we got dns error

please help