Can't remote connect to sql server

I have SQL Sever 2008 R2 on the cluster environment

cluster server name is A
Cluster Node 1 name is A1 (current active one)
Cluster Node2 name is A2

SQL Server name is Ab, default instance, tcp/ip port 1433

I am not able to remote connect to the server. I tried A, A1, Ab and their corresponding IP address, not of them works. Should I change to the SQL Server name to match with the cluster server name? Thanks in advance!