Chapter 7 Service Configuration
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Spanning Tree Protocol (STP) can calculate accoding to the
protocol. divide the ports into different parts:
Master:the port type introduced in MSTP protocol. When
multiple different areas exist, the main port is the minimal
pathcost port point to the root.
Designated:the port transmits data to switch downward, &
send STP protocol message to maintain the state of STP.
Backup:the port receives the STP message. To prove that
there exits a loop route to the port itself.
Alternate:the port receives excess STP protocol message
from other equipment . But when the original link
abnormally lost, the port under this state can transfer to
transmitting state, & maintain the network instead of the
port lapsed.
Edged:the port used to connect the terminal equipment,
such as PC. The port set as the margin port do not
participate in calculation when STP is turbulent & the state
can switch fast.
According to port role, the state after the calculation being
steady is shown in
TABLE147 .
TABLE147 PORT ROLE & PORT STATE
Port role Port state
Master Forward
Root Forward
Designated Forward
Backup Discard
Alternate Discard
Edged Forward
Spanning Tree Protocol (STP) is applicable to a loop network.
It blocks some redundant paths with certain algorithms so that
the loop network is pruned into a tree network without any loop,
thus avoiding the hyperplasia and infinite loop of packets in the
loop network.
BPDU protect function is a particular protection for margin port.
The margin port will not receive the protocol message . If there
exists vicious protocol attack or Linux virtual bridge, receiving
unlawful protocol message will bring to net shocking or topology
changing abnormally. The port will be closed after using the
protection. After a while, to check the net is normal or not. If
it is normal, it will recovery to original state.
Root protection is function is a particular protection for root
switch. In the network that needs to appoint switch as root
STP
BPDU
Protection
Root
Protection
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