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RSTP
Rapid Spanning
Tree Protocol
RSTP
You must first Enable STP/RSTP mode, before configuring any related parameters. Parameter settings
required for both STP and RSTP are the same. 802.1d refers to STP mode, while 802.1w refers to faster
RSTP mode.
Bridge Configuration
Priority (0-61440) RSTP uses bridge ID to determine the root bridge, the bridge with the highest bridge ID becomes the
root bridge. The bridge ID is composed of bridge priority and bridge MAC address. The bridge with the
highest priority becomes the highest bridge ID. If all the bridge IDs have the same priority, the bridge
with the lowest MAC address then becomes the root bridge.
Note: The bridge priority value must be in multiples of 4,096. A device with a lower number has a
Max Age (6-40)
Enter a value from 6 to 40 seconds here. This value represents the time that a bridge waits without
receiving Spanning Tree Protocol configuration messages before attempting to reconfigure.
If the RocketLinx ES7528 is not the root bridge, and if it has not received a hello message from the root
bridge in an amount of time equal to Max Age, then the RocketLinx ES7528 reconfigures itself as a root
bridge. Once two or more devices on the network are recognized as a root bridge, the devices
renegotiate to set up a new spanning tree topology.
Hello Time (1-10) Enter a value from 1 to 10 seconds here. This is a periodic timer that drives the switch to send out Bridge
protocol data unit (BPDU) packet to check current STP status. The root bridge of the spanning tree
topology periodically sends out a "hello" message to other devices on the network to check if the
topology is "healthy". The "hello time" is the amount of time the root has waited during sending hello
messages.
BPDUs are data messages that are exchanged across the switches within an extended LAN that uses a
spanning tree protocol topology. BPDU packets contain information on ports, addresses, priorities and
costs and ensure that the data ends up where it was intended to go. BPDU messages are exchanged
across bridges to detect loops in a network topology. The loops are then removed by shutting down
selected bridge interfaces and placing redundant switch ports in a backup, or blocked, state.
Forward Delay
Enter a value between 4 and 30 seconds. This value is the time that a port waits before changing from
Time (4-30)
Spanning Tree Protocol learning and listening states to forwarding state. This is the amount of time the
RocketLinx ES7528 waits before checking to see if it should be changed to a different state.
Note: You must observe the following rule to configure Hello Time, Forwarding Delay, and Max Age parameters.
2 × (Forward Delay Time – 1 sec) ≥ Max Age Time ≥ 2 × (Hello Time value + 1 sec)
Port Configuration
Admin Path Cost
Enter a number between 1 and 200,000,000. This value represents the cost of the path to the other bridge
from the transmitting bridge at the specified port.
Priority
Enter a value between 0 and 240, using multiples of 16. This is the value that decides which port should
be blocked by priority in a LAN.
Admin P2P
Some of the rapid state transitions that are possible within RSTP depend upon whether the port of
concern can only be connected to another bridge (that is, it is served by a point-to-point LAN segment),
or if it can be connected to two or more bridges (i.e, it is served by a shared-medium LAN segment).
This function allows P2P status of the link to be manipulated administratively. Auto means to auto
select P2P or Share mode. P2P means P2P is enabled, while Share means P2P is disabled.
Admin Edge
A port directly connected to the end stations cannot create a bridging loop in the network. To configure
this port as an edge port, set the port to the Enable state. When the non-bridge device connects an admin
edge port, this port is in a blocking state and turns to a forwarding state in 4 seconds.
70 - RocketLinx ES7528 Industrial Managed PoE Rack Mount User Guide: 2000509 Rev. A
higher bridge priority. Ex: 4096 is higher than 32,768.
Description
RSTP
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