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RSTP
RSTP is defined by the IEEE 802.1w standard and downward compatible with IEEE 802.1d STP.
In addition to a loop-free network and redundant links, it features with fast convergence. If all
bridges in a LAN support RSTP, it enables a rapid topology tree generation when the network
topology changes (traditional STP topology tree: 50 seconds, RSTP topology tree: 1 second).
RSTP determines the network topology by exchanging BPDUs among switches. However, the
BPDU format of RSTP differs from that of STP. When the topology is changing, RST-BPDU
messages are spread by floods to notify the change to the whole network.
Conditions for rapid state migration of the root ports and designated ports in RSTP:
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Root port: The original root port of the switch stops forwarding data and the
designated port of the upstream switch begins to forward data.
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Designated port: If the designated port is an edge port, it can directly transit to
forwarding state; if the designated port is a P2P port, it can transit to forwarding
state once it gets response from the downstream switch through handshake.
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Edge Port
An edge port is a designated port on the edge of the switching network. It is directly connected
to terminal devices. An edge port can transit to forwarding state immediately without going
through listening and learning states. If it receives a BPDU, it immediately turns from an edge
port to a common spanning tree port, and joins the STP generation.
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P2P Port
A P2P port used to connect to other switches. Under RSTP/MSTP, all ports operating in full-
duplex mode are P2P ports.
9.3.2 STP global settings
Click Device Management > STP > Global Settings to enter the page.
Chapter 9 Device management 37