The switch which has the lowest bridge ID can be the root bridge,and the bridge ID is made of priority and MAC address,that is ,

bridge ID = priority + MAC address
So we will choose the switch which has the lowest priority to be the root bridge,if priority of all switches are the same,we will choose the switch which has the lowest MAC address to be the root bridge.

So my question are

**1**. Why should we choose the switch which has **"the lowest"** bridge ID to be the root bridge,not **"the highest"** ?

**2**.Why can one of switches has the lower priority?if priority can change,then base on what reason,so we let this switch has the lower or lowest priority ? The position in the topology? the performance of switch?