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Advanced Settings
resulting BPDU;
If the BPDU of this port takes the precedence over the resulting BPDU,
the BPDU of this port is not replaced and the port is blocked. The port only
can receive BPDUs.
Tip:
In a STP with stable topology, only the root port and designated port can forward data, and
the other ports are blocked. The blocked ports can only receive BPDUs.
STP Timer
1
．
Hello Time
Hello Time ranges from 1 to 10 seconds. It specifies the interval to send BPDU packets. It
is used to test the links.
2
．
Max Age
Max Age ranges from 6 to 40 seconds. It specifies the maximum time the switch can wait
without receiving a BPDU before attempting to reconfigure.
3
．
Forward Delay
Forward Delay ranges from 4 to 30 seconds. It specifies the time for the port to transit its
state after the network topology is changed.
When the STP regeneration caused by network malfunction occurs, the STP structure will
get some corresponding change. However, as the new configuration BPDUs cannot be
spread in the whole network at once, the temporal loop will occur if the port transits its
state immediately. Therefore, STP adopts a state transit mechanism, that is, the new root
port and the designated port begins to forward data after twice forward delay, which
ensures the new configuration BPDUs are spread in the whole network.
RSTP
RSTP (Rapid Spanning Tree Protocol), evolved from the 802.1D STP standard, enable
Ethernet ports to transit their states rapidly (traditional STP: 50s; RSTP: 1s). The premises
for the port in the RSTP to transit its state rapidly are as follows.
The condition for the root port to transit its port state rapidly: The old root port of the
switch stops forwarding data and the designated port of the upstream switch begins
to forward data.
The condition for the designated port to transit its port state rapidly: The designated
port is an edge port or connecting to a point-to-point link. If the designated port is an
edge port, it can directly transit to forwarding state; if the designated port is
