XS26GS Managed Optical Ethernet Switch User Manual
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the spanning tree will be recalculated at BPDU packet times out. When a switch becomes
a root bridge, it regularly sends BPDUs at the interval specified by this hello time. A
non-root-bridge switch adopts the interval specified by this hello time.
Max Age
: this value is in the range from 6 to 40 seconds, and is 20 seconds by default.
MSTP is capable of detecting link failures and automatically restoring redundant links to
the forwarding state. In CIST, switches use max age parameter to determine whether a
received configuration BPDU times out. Spanning trees will be recalculated if a
configuration BPDU received by a port times out.
Forward Delay Time
: this value is in the range from 4 to 30 seconds, and is 15 seconds
by default.
To prevent the occurrence of a temporary loop, when a port changes its state from
discarding to forwarding, it undergoes an intermediate state and waits for a specific
period of time to synchronize with the state transition of the remote switches. This state
transition period is determined by
Forward Delay Time
configured on the root bridge,
and applies to all non-root bridges.
As for the configuration of
Hello Time, Forward Delay Time, and Max Age
, the
following formulas must be met to prevent frequent network jitter:
2
×
(
Forward Delay Time
– 1 second) >=
Max Age
, and
Max Age
>= 2
×
(
Hello
Time
+ 1 second).
Priority
: this value is in the range from 0 to 65535, and is 32768 by default. This
parameter is used in STP and RSTP modes only.
BPDU Guard
: some ports are usually configured as edge ports to achieve rapid
transition, while they will resume non-edge ports automatically upon receiving
configuration BPDUs, which may cause spanning trees regeneration and network
topology jitter.
Normally, no configuration BPDU will reach edge ports, but malicious users can attack a
network by sending configuration BPDUs deliberately to edge ports to cause network
jitter, which can be prevented by utilizing this BPDU protection function. With this
function enabled on a switch, the switch shuts down the edge ports that receive
configuration BPDUs and then reports the cases to the network administrator. After a
port is shut down, only the administrator can restore it.
By default, the BPDU protection function is disabled.
2.12.2
STP&RSTP
2.12.2.1
Ports Configuration
This page sets STP enabling, Edge Port, P2P, Migration, Tx Hold Count, External Cost,
