Specifying the IP address to be used when connecting to an instance
Have a look at How to setup and use a SQL Server alias

Excerpts below:


  Problem
  
  I have an application that has a specified database connection that I
  either can't or don't want to change. However, I need to move the
  database to a new server. How can I do this easily without breaking
  other things that maybe using this connection and/or database?
  
  Solution
  
  By using an alias, we can keep the application configuration the same,
  but tell the operating system to look somewhere else for the database.
  One proviso is that once an alias is created, it is set at the
  operating system level. That means if we have two applications which
  connect to MySQLServer on that computer, once the alias is created,
  both will be re-pointed based on the alias. You can create an alias
  using one of two utilities:
  
  
  SQL Server Configuration Manager
  SQL Server Client Network Utility
  
  
  SQL Server Configuration Manager
  
  Let's start by looking at how to do it using SQL Server Configuration
  Manager. In the left pane of SQL Server Configuration Manager, if you
  expand the SQL Native Client Configuration folder, there is a
  subfolder called Aliases (see Figure 1). If we click on this
  subfolder, we'll see any aliases that have been defined for the system
  shown in the right pane. In most cases, there won't be any defined. To
  create a new alias, right-click on Aliases and choose New Alias...
  from the pop-up menu.


Figure 1:




  A dialog window comes up (Figure 2) which allows us to specify our new
  alias. In the Alias Name property, you specify the name the
  application uses. For instance, if it connects to a SQL Server called
  MyOldServer, that's what you enter in here. You can also enter an
  alias that appears to point to a named instance, such as
  MyOldServer\MyInstance. You can then specify the server where the
  database really is, to include configuring the protocol, the server
  name, and the port. Clicking the OK button will create the alias. In
  the case of Figure 2, I'm creating an alias called MyOldServer which
  points to my local server's default instance.


Figure 2:




  You should now see the new alias listed in the right pane (Figure 3).





  The next step is to test the connection. You can do so quickly by
  either creating and testing a Data Source Name (DSN), or if you have
  the SQL Server client tools installed, by using SQL Server Management
  Studio (SSMS). I'll do so using SSMS. Figure 4 shows the dialog window
  to open a new connection to a database engine. For Server name:, enter
  in the alias you specified. In the example we called the alias
  OldServerName, so that's what we'll use here.
  
  Figure 4:





  If the alias is pointed correctly to the new location, a successful
  connection should be established. In SSMS, I was opening a new
  connection for Object Explorer. Figure 5 shows that the connection was
  successfully made using the alias. Note that as far as SSMS is
  concerned, the server name is the alias.
  
  Figure 5: