•
Instance
– Instance identifier of this spanning tree. (This is alwa ys 0 for th e CI ST .)
• VLANs configuration – VLANs assigned to the CIST.
• Priority – Bridge priority is used in selecting the root device, root po rt, and
designated port. The device with the highest priority (i.e., lower n umeric value )
becomes the STA root device. However, if all devices have the sa me priority, the
device with the lowest MAC address will then become the root device .
• Root Hello Time – Interval (in seconds) at which this d evice tran smits a
configuration message.
• Root Maximum Age – The maximum time (in seconds ) this devi ce can wait
without receiving a configuration message before attempting to reconfigure. All
device ports (except for designated ports) should receive configuratio n mes sages
at regular intervals. If the root port ages out STA information (prov ided in the las t
configuration message), a new root port is selected from among the device ports
attached to the network. (References to “ports” in this section means “interfac es,”
which includes both ports and trunks.)
•
Root Forward Delay
– The maximum time (in seconds) this device will wait before
changing states (i.e., discarding to learning to forwarding). This delay is required
because every device must receive information about topology changes befor e it
starts to forward frames. In addition, each port needs time to listen for conflicting
information that would make it return to a discarding state ; otherwise, temporary
data loops might result.
• Max hops – The max number of hop counts for the MST region .
• Remaining hops – The remaining number of hop counts for t he MST inst ance.
• Transmission limit – The minimum interval betw een the transmiss ion of
consecutive RSTP/MSTP BPDUs.
• Path Cost Method – The path cost is used to determine the best path be tween
devices. The path cost method is used to determine the range of values th at can
be assigned to each interface.
Web
– Click Spanning Tree, STA, Information.
Figure 10-1 STA Information
10-4
Spanning Tree Algorithm
10