address will then become the root device. (Note that lower numeric values indicate
higher priority.)
• Default: 32768
• Range: 0-61440, in steps of 4096
• Options: 0, 4096, 8192, 12 288, 16 384, 20480, 24576, 28672 , 32768, 36864,
40960, 45056, 49152, 53248, 57344, 61440
Root Device Configuration
• Hello Time – Interval (in se conds) at w hich th e root dev ice transm its a
configuration message.
• Default: 2
• Minimum: 1
• Maximum: The lower of 10 or [(Max. Message Age / 2) -1]
• Maximum Age – The maxim um time (in se conds) a device can wait withou t
receiving a configuration message before attempting to reconfigure. All device
ports (except for designated ports) should receive configuration mess ages at
regular intervals. Any port that ages out STA information (provided in the last
configuration message) becomes the designated port for th e attac hed LAN. If it is
a root port, a new root port is selected from among the device ports attached to the
network. (References to “ports” in this section mean “i nterfa ces,” which incl udes
both ports and trunks.)
• Default: 20
• Minimum: The higher of 6 or [2 x (Hello Time + 1)].
• Maximum: The lower of 40 or [2 x (Forward Delay - 1)]
• 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.
• Default: 15
• Minimum: The higher of 4 or [(Max. Messag e Age / 2) + 1]
• Maximum: 30
Configuration Settings for RSTP
The following attributes apply to both RSTP and MSTP:
• Path Cost Metho d – The path co st is used to det ermine the best path between
devices. The path cost method is used to determi ne the ra nge of v alues th at can
be assigned to each interface.
- Long: Specifies 32- bit based v alues that rang e from 1-200,0 00,000.
(This is the default.)
- Short: Specifies 16-bit based va lues that r ange fro m 1-65535.
•
Transmission Limit
– The maximum transmission rate for BPDUs is specified by
setting the minimum interval between the transmission of consecutive protocol
messages. (Range: 1-10; Default: 3)
10-7Configuring Global Settings
10