By default, we can see every instance of SQL Server on the network. The network broadcast is what enables the instance enumeration within various management tools where you can utilize a drop down to select an instance. SQL Server Browser Service makes this more convenient.
If you want to list out all SQL server Instances in your Network use the below mentioned query:
EXEC master..XP_CMDShell 'OSQL -L'
But there are many cases, particularly in production environments, where you want to hide your instance of SQL Server or in other words, where you do not want SQL Server to broadcast its presence.
Hiding an instance is done for security purposes. This would force an attacker to scan IP ranges in an attempt to locate SQL Servers which can be easily identified & mitigated by your Netowrk Admin. Unfortunately, the option to disable the broadcast is hidden away. But you can easily do so by following the below mentioned steps:
To disable the broadcast,
Launch SQL Server Configuration Manager.
Open the Network Configuration section.
Right click on the Protocols for the instance you want.
You will see a flag value labeled Hide Instance.
Set this value to Yes.