HP 1920 Gigabit Ethernet Switch Series User Manual page 207

Item
Mode
Max Hops
Path Cost Standard
Bridge Diameter
Timers
Instance (Instance ID,
Root Type, and Bridge
Priority)
Description
Sets the operating mode of STP:
•
STP—Each port on a device sends out STP BPDUs.
•
RSTP—Each port on a device sends out RSTP BPDUs, and automatically
migrates to STP-compatible mode when detecting that it is connected with a
device running STP.
•
MSTP—Each port on a device sends out MSTP BPDUs, and automatically
migrates to STP-compatible mode when detecting that it is connected with a
device running STP.
Sets the maximum number of hops in an MST region to restrict the region size.
The setting can take effect only when it is configured on the regional root
bridge.
Specifies the standard for path cost calculation. It can be Legacy, IEEE
802.1D-1998, or IEEE 802.1T.
Any two stations in a switched network are interconnected through a specific
path composed of a series of devices. The bridge diameter (or the network
diameter) is the number of devices on the path composed of the most devices.
After you set the network diameter, you cannot set the timers. Instead, the
device automatically calculates the forward delay, hello time, and max age.
When you configure the bridge diameter, follow these guidelines:
•
The configured network diameter is effective on CIST only, not on MSTIs.
•
The bridge diameter cannot be configured together with the timers.
Configure the timers:
•
Forward Delay—Set the delay for the root and designated ports to transit to
the forwarding state.
•
Hello Time—Set the interval at which the device sends hello packets to the
surrounding devices to make sure the paths are fault-free.
•
Max Age—Set the maximum length of time a configuration BPDU can be
held by the device.
When you configure timers, follow these guidelines:
•
The settings of hello time, forward delay and max age must meet a certain
formula. Otherwise, the network topology will not be stable. HP
recommends you to set the network diameter and then have the device
automatically calculate the forward delay, hello time, and max age.
•
The bridge diameter cannot be configured together with the timers.
Sets the role of the device in the MSTI or the bridge priority of the device, which
is one of the factors deciding whether the device can be elected as the root
bridge.
Role of the device in the MSTI:
•
Not Set—Not set (you can set the bridge priority of the device when
selecting this role)
•
Primary—Configure the device as the root bridge (you cannot set the bridge
priority of the device when selecting this role)
•
Secondary—Configure the device as a secondary root bridge (you cannot
set the bridge priority of the device when selecting this role).
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