WAGO-ETHERNET-Zubehör 852
Enhanced Features
89
852-1305 8/4-Port 100BASE-T/1000BASE-SX/LX
Manual
1.1.0
7.2.13 STP
The (R)STP (“(
R
apid)
S
panning
T
ree
P
rotocol)”) can detect and stop network
loops, as well as provide “Backup Links” between switches, bridges or routers. It
allows a switch to interact with other (R)STP-compliant switches in the network
to ensure that only one path exists between any two stations on the network.
The switch supports both STP and RSTP as defined in the following standards:
•
IEEE 802.1D Spanning Tree Protocol
•
IEEE 802.1w Rapid Spanning Tree Protocol
The switch uses IEEE 802.1w RSTP that allows faster convergence of the
“Spanning Tree” than STP (the switch is also backwards compatible with STP-
only aware bridges). In RSTP, topology change information is directly propagated
throughout the network from the device that generates the topology change. In
STP, there are longer delays because the device that causes a topology change
first notifies the “Root Bridge” and then the network. Both RSTP and STP remove
unwanted learned addresses from the filtering database.
•
STP has the port states “Blocking”, “Listening”, “Learning” and
“Forwarding”.
•
RSTP has the port states in RSTP “Discarding”, “Learning” and
“Forwarding”.
STP Switch Port States
•
“Blocking”
If a port causes a “Switching Loop” (looping connection between two
ports), user data can no longer be sent or received. However, the port can go
into the “Forwarding” state if the other active connections fail and the
“Spanning Tree” algorithm determines that the port may transition to that
state. BPDU data is still received and sent in the “Blocking” state.
•
“Listening”
The switch processes BPDUs and waits for possible new information that
would cause it to return to the “Blocking” state.
•
“Learning”
Even if the port does not yet forward any frames (packets), it can learn
source addresses from frames received and add them to the filter database
(“Switching Database”).
