Scenario:
  Suppose you are having two server SERVER A  (web application server) and SERVER B (SQL database server).
Your client wants to use upgraded Machine for SQL server (SERVER C). First you need to restore the databases from Sql server B to SQL server C.
Web application Server A contains 1000+ web sites, who are using SERVER B database. Imagine, how many web.config files you would be required to update
and applications whose connection strings not stored in web.config.

Here is how quickly we can make system live using SQL server nework utility.

MS SQL SERVER  CLICONFG

Using Sql server network utility we can route the traffic to new sql server without changing
any application configuration.

Go to your web application Server A and follow below commands.

Fig.1.

It will open SQL server client network utility.

Fig.2.

Click on add then click on TCP/IP

e.g.

All applications are accessing SQL server using IP 192.168.1.1.
Now, let’s say it is changed to 192.168.1.2.

Below fig shows how to configure application server to use new IP, instead of doing changes in all web.config / App.config or any hard coded IP.

Fig.3.

If applications are accessing SQL using domain or name of sql server. use Named Pipes.

Here you can see, you are not only just be able to route the traffic to IP but also to ports,
This is very useful utility.