Simple Queue for my VOIP PBX

What is the most efficient way to guranantee 1meg of bandwidth to my VOIP PBX IP interface?

My Lan IP is 192.168.2.0/24, The PBX is 192.168.2.252. I need to gurarantee the my users cannot rob the necessary bandwidth from my PBX to operate properly.

Do i make a simple queue for .252 and give it a higher priority then 192.168.2.0/24 ?



Thank you