SSAS 2005 with static port

Hi All, 

I have many SSAS 2005 instances on a server.

Out of which, 1 instance has a static port:

<Port>2387</Port>

But I can connect to this instance without specifying the port, locally as well as remotely using SSMS as below:

Servername\SSASinstance (without PORT number)

Of course, I can connect with PORT number also, by 

Servername:PORTnumber (without PORT number)

How is this possible? I should need to always use the port number, right?

Thanks in advance, 
Mandar