HP 1920 Gigabit Ethernet Switch Series User Manual

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• Forward delay—Delay that STP bridges use to transit port state.
The descriptions and examples in this chapter only use the following fields in the configuration BPDUs:
• Root bridge ID (represented by device priority)
• Root path cost
• Designated bridge ID (represented by device priority)
• Designated port ID (represented by port name)
Basic concepts in STP
Root bridge
A tree network must have a root bridge. The entire network contains only one root bridge, and all the
other bridges in the network are called "leaf nodes". The root bridge is not permanent, but can change
with changes of the network topology.
Upon initialization of a network, each device generates and periodically sends configuration BPDUs,
with itself as the root bridge. After network convergence, only the root bridge generates and periodically
sends configuration BPDUs. The other devices only forward the BPDUs.
Root port
On a non-root bridge, the port nearest to the root bridge is the root port. The root port communicates with
the root bridge. Each non-root bridge has only one root port. The root bridge has no root port.
Designated bridge and designated port
Classification Desi
g
nated brid
g
e Desi
g
nated
p
ort
For a device
Device directly connected with the local
device and responsible for forwarding
BPDUs to the local device.
Port through which the designated bridge
forwards BPDUs to the local device.
For a LAN
Device responsible for forwarding BPDUs to
this LAN segment.
Port through which the designated bridge
forwards BPDUs to this LAN segment.
As shown in Figure 173, Device B and Device C are connected to the LAN. AP1 and AP2, BP1 and BP2,
and CP1 and CP2 are ports on Device A, Device B, and Device C, respectively.
• If Device A forwards BPDUs to Device B through AP1, the designated bridge for Device B is Device
A, and the designated port of Device B is port AP1 on Device A.
• If Device B forwards BPDUs to the LAN, the designated bridge for the LAN is Device B, and the
designated port for the LAN is the port BP2 on Device B.

HP 1920 Gigabit Ethernet Switch Series Specifications

General

Brand	HP
Model	1920 Gigabit Ethernet Switch Series
Category	Switch
Language	English