Networkdevice configuration: reboot necessary?

[Karl Sinn]

Hi,

I went on with the configuration of my first FreeBSD computer. And I found 
something amazing:

After the configuration of the network device with sysinstall the network did 
not work immediately.
In the handbook it is written to reboot after configuration.

Is this really necessary? 
Is there no other way to change the configuration without turning of the 
computer?

Thanks
Karl