Global

With this dialog you can:

Note: Rapid Spanning Tree is activated on the device by default, and it automatically begins to resolve the existing topology into a tree structure. If you have deactivated RSTP on individual devices, you avoid loops during the configuration phase.

The following tables show the selection options and default settings, and information on the global Spanning Tress settings for the bridge.

Tab. Global Spanning Tree settings, basic function

Parameters

Meaning

Possible values

Default setting

Frame „Function“

Switches the Spanning Tree function for this device “On” or “Off”.
If you switch off the Spanning Tree for a device globally, the device floods the Spanning Tree packets received like normal Multicast packets to the ports. Thus the device behaves transparently with regard to Spanning Tree packets.

On,
Off

On

Frame „Protocol Version“

Select the protocol version:
- RSTP (IEEE 802.1Q-2005), to use the Spanning Tree jointly for all configured VLANs,
- MSTP (IEEE 802.1Q-2005), to use the Spanning Tree separately for various VLAN groups.

RSTP, MSTP

RSTP


In the “Protocol Configuration / Information” frame you can configure the following values and read information.

In the context of MSTP, these are the settings for the Common Spanning Tree (CST).

Tab. Global Spanning Tree settings, local bridge parameters

Parameters

Meaning

Possible values

Default setting

Column „Bridge“

Information and configuration parameters of the local device

Bridge ID (read only)

The local Bridge ID, made up of the local priority and its own MAC address.

The format is ppppp / mm mm mm mm mm mm,
with: ppppp: priority (decimal) and mm: the respective byte of the MAC address (hexadecimal).

Priority

Sets the local bridge priority.
The bridge priority and its own MAC address make up this separate Bridge ID. The device with the best (numerically lowest) priority assumes the role of the root bridge. Define the root device by assigning the device the best priority in the Bridge ID among all the devices in the network.
Enter the value as a multiple of 4096.

0 ≤ n*4096 ≤
61440

32768

Hello Time

Sets the Hello Time.
The local Hello Time is the time in seconds between the sending of two configuration messages (Hello packets).

If the local device has the root function, the other devices in the entire network take over this value. Otherwise the local device uses the value of the root bridge in the “Root” column on the right.

1 - 2

2

Forward Delay

Sets the Forward Delay parameter.
In the previous STP protocol, the Forward Delay parameter was used to delay the status change between the statuses disabled, discarding, learning, forwarding. Since the introduction of RSTP, this parameter has a subordinate role, because the RSTP bridges negotiate the status change without any specified delay.

If the local device is the root, the other devices in the entire network take over this value. Otherwise the local device uses the value of the root bridge in the “Root” column on the right.

4 - 30 s

See the note following this table.

15 s

Max Age

Sets the Max Age parameter.
In the previous STP protocol, the Max Age parameter was used to specify the validity of STP BPDUs in seconds. For RSTP, Max Age signifies the maximum permissible branch length (number of devices to the root bridge).

If the local device is the root, the other devices in the entire network take over this value. Otherwise the local device uses the value of the root bridge in the “Root” column on the right.

6 - 40 s

See the note following this table.

20 s

Tx Hold Count

Sets the Hx Hold Count parameter.
If the device sends a BPDU, it increments a counter at this port. When the counter reaches the value of the Tx Hold Count, the port stops sending any more BPDUs.
The counter is decremented by 1 every second. The device sends a maximum of 1 new BPDU in the following second.

1 - 40
(based on RSTP standard: 1 - 10)

10

MRP compatibility

Switches the MRP compatibility on/off.
MRP compatibility enables RSTP to be used within an MRP-Ring and when coupling RSTP segments to an MRP-Ring. The prerequisite is that all devices in the MRP-Ring must support MRP compatibility.

On, Off

Off

BPDU Guard

Switches the BPDU Guard function on/off.
If BPDU Guard is switched on, the device automatically activates the function for edge ports (with the setting “Admin Edge Port” true). When such a port receives any STP-BPDU, the device sets the port status “BPDU Guard Effect” to true and the transmission status of the port to discarding'Port-related STP settings and displays, guards'.

Thus the device helps you protect your network at terminal device ports from incorrect configurations or attacks with STP-BPDUs that try to change the topology.

On, Off

Off


Note: If you combine RSTP with an MRP-Ring, you must give the devices in the MRP-Ring a better (i.e. numerically lower) RSTP bridge priority than the devices in the connected RSTP network. You thus help avoid a connection interruption for devices outside the Ring.
Note: The parameters Forward Delay and Max Age have the following relationship:Forward Delay ≥ (Max Age/2) + 1If you enter values that contradict this relationship, the device then replaces these values with the last valid values or the default value.

Tab. Global Spanning Tree settings, root bridge information

Parameters

Meaning

Possible values

Default setting

Column „Root“

Information on the device that is currently the root bridge

Bridge ID

The Bridge ID of the current root bridge.

The format is ppppp / mm mm mm mm mm mm,
with: ppppp: priority (decimal) and mm: the respective byte of the MAC address (hexadecimal).

Priority

The Priority of the current root bridge.

0 ≤ n*4096 ≤
61440

32768

Hello Time

The Hello Time of the current root bridge.

1 - 2

2

Forward Delay

The Forward Delay of the current root bridge.

4 - 30 s

15 s

Max Age

The Max Age of the current root bridge.

6 - 40 s

20 s


Tab. Global Spanning Tree settings, topology information

Parameters

Meaning

Possible values

Column „Topology“

Spanning Tree topology information

Bridge is root

If the local device is currently the root bridge, the device displays this box as selected, and otherwise as empty.

Selected, not selected.

Root Port

The port of the device from which the current path leads to the root bridge. 0: the local bridge is the root.

Valid port ID or 0.

Root path costs

Path costs from the root port of the device to the current root bridge of the entire layer 2 network. 0: the local bridge is the root.

0-200000000

Topology change count

Counts how often the device has put a port into the Forwarding status via Spanning Tree since it was started.

 

Time since last change

Time since the last topology change.

 

If you have activated the “MRP Compatibility” function, the device displays the “Information” frame with additional information on MRP compatibility:

Tab. Global Spanning Tree settings, Information frame

Parameters

Meaning

Possible values

Default setting

Information

If you have activated the MRP compatibility (RSTP over MRP) and one of the participating devices has detected a configuration problem, the device displays “Conflict with bridge pppp / mm mm mm mm mm”. During normal operation, this field is empty.

Message with bridge ID or empty.

-


Buttons

Tab. Buttons (Forts.)

Button

Meaning

“Set”

Transfers the changes to the volatile memory (RAM) of the device. To permanently save the changes, open the Basic Settings:Load/Save dialog, select the location to save the configuration, and click “Save”.

“Reload”

Updates the fields with the values that are saved in the volatile memory (RAM) of the device.

“Help”

Opens the online help.