For the clearness of this problem i paste the answer of support below.
[quote]Re: Creating an alias to dreamhost nameservers
You need to add A records pointing to the IPs of our nameservers. For
instance, for ns1.schietschijf.be you would add this in your zone:
ns1 A 188.8.131.52
If you have any other questions or concerns, be sure to let me know!
so go to manage domains, click the dns-link for the domain.
Then you type the name “your” nameserver should have and select “A” as type and as value you insert the ip of the nameserver of dreamhost.
so mine says:
[quote]ns1  [X] A 184.108.40.206
ns2  [X] A 220.127.116.11
ns3  [X] A 18.104.22.168[/quote]