MSTP (Multiple Spanning Tree)

With this dialog you can:

The tab for the global Multiple Spanning Tree Instance is named “MST Global (CIST)”. This instance is always available and cannot be deleted. It contains all the configured VLANs that are not explicitly assigned to an MSTI. The settings include the MST region identifier, the maximum number of Hops for the Internal Spanning Tree (IST), and information on IST and CST (known in combination as CIST).

The tabs for the MSTIs are named MSTI, followed by the number of the instance, e.g. “MSTI 2”. Here you can manage the individual Multiple Spanning Tree Instances (MSTIs). The device allows you to create up to 16 Multiple Spanning Tree Instances (MSTIs). The prerequisite for using MSTP is that all the bridges in the network that make up an MSTP region must also support MSTP.

Note: To use MSTP, disable the other redundancy protocols on this device.
Note: When combining MSTP with the management VLAN 0, note the following restriction: the DHCP client of the device only sends its DHCP Broadcasts in VLAN 1.

Dialog Tab MSTP Global (CIST)

This tab in the dialog allows you to configure the MST region and the global Multiple Spanning Tree Instance (IST) within the MST region, and to display information on IST and CST.

Tab. Dialog Multiple Spanning Tree settings, MST Global, MST region identifier

Parameters

Meaning

Possible values

Default setting

"MST Region Identifier" Frame

Information about the MST region

   

Name

Name of the MSTP region to which the device belongs.

Max. 32 characters, value 0x21 (!) up to and incl. 0x7e (~)

The MAC address of the device.

Revision level

Version number of the MSTP region to which the device belongs.

0 -65535

0

Digest

The MD5 checksum of the MSTP configuration.

16 bytes in hexadecimal.

 

Note: Configure all the bridges of an MST region with identical values for:
Note: Include the ports that connect the bridges of an MST region as tagged members in all the VLANs that are set up on the bridges. You thus avoid potential connection breaks when the topology is changed within the MST region.
Also include the ports that connect an MST region with other MST regions or with the CST region (known as boundary ports) as tagged members in all the VLANs that are set up on both regions. You thus avoid potential connection breaks when topology changes affecting the boundary ports are made.

Tab. Dialog Multiple Spanning Tree settings, MST Global (CIST), Global MST parameters

Parameters

Meaning

Possible values

Default setting

Frame „Global CIST Parameters“

Detailed information on the global MST instance (IST) for the region and CST.

   

Maximum Hops

Maximum number of bridges within the MST region in a branch to the root bridge.

6-40

20

Attached VLANs

List of all VLANs that are assigned only to the global MST instance and to no other MSTI.

List of all static VLANs.

1;

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).

Root ID

The Bridge ID of the current root bridge of the entire layer 2 network.a

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

Regional Root ID

The Bridge ID of the current root bridge that belongs to the global instance (IST) of the MST region to which this device belongs.b

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

   

Root Port

The port of the device from which the current path leads to the root bridge of the entire layer 2 network (CIST root). 0: local bridge is CIST root.

Valid port ID or 0

-

Root path costs

External path costs from the regional root bridge of the MST region of the device to the current root bridge of the entire layer 2 network (CIST root).c These are the same for all devices within an MST region. 0: Regional root bridge is simultaneously CIST root bridge

0-200000000

 

Internal root path costs

Internal path costs from the root port of the device to the current regional root bridge of the MST region of the device. 0: local bridge is root.

0-200000000

-


MSTI (Multiple Spanning Tree Instance) dialog tab

The MSTI tabs in the dialog allow you to manage the individual Multiple Spanning Tree Instances. The tab is named MSTI, followed by the number of the instance, e.g. “MSTI 2”.

Tab. Multiple Spanning Tree settings, MST Instance, VLANs

Parameters

Meaning

Possible values

Default setting

Frame „VLANs“

Manage the VLANs assigned to this Multiple Spanning Tree Instance.

   

Assigned VLANs

List of all VLANs currently assigned to this MSTI.

Subset of all statically set up VLANs.

No VLANs.

“Add VLAN” button

Opens a dialog for selecting a VLAN ID from the statically set up VLANs of the device. Select the desired VLAN ID and click on “OK”.

One of the static VLANs.

 

“Remove VLAN” button

Opens a dialog for selecting a VLAN ID. Select the desired VLAN ID and click on “OK”.

A VLAN currently assigned to the MSTI

 

Tab. Multiple Spanning Tree settings, MST Instance, parameters

Parameters

Meaning

Possible values

Default setting

Frame „Instance Parameters“

Detailed information on the selected Multiple Spanning Tree Instance.

   

Priority

The local bridge Priority for the selected MST Instance. The bridge priority and its own MAC address make up this separate Bridge ID. The device with the best (i.e. numerically lowest) priority becomes the root device of the selected MST region. Define the root device by assigning to this device the best priority in the Bridge ID among all the devices in the selected MST region.
Enter the value as a multiple of 4096.

0 ≤ n*4096 ≤
61440

32768

Bridge ID

The local Bridge ID, made up of the local priority + MSTI, following by its own MAC address.

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

0 - 65534; sum of priority (0 - 61440 in steps of 4096) and MSTI (1 - 4094)

32768 + MSTI

Time since last change

Time since the last topology change for this MST Instance.

   

Topology changes

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

   

Root ID

The Bridge ID of the current root bridge of the selected MST region.

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

0 - 65534; sum of priority (0 - 61440 in steps of 4096) and MSTI (1 - 4094)

Root path costs

Path costs from the root port to the current root bridge of the selected MST region. 0: bridge is root for this MST region.

0-200000000

 

Root Port

The port of the device from which the current path leads to the root bridge of the selected MST region. 0: bridge is root for this MST region.

Valid port ID or 0

 

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.

“Create”

Adds a MSTP instance.

“Remove”

Removes a MSTP instance.

“Help”

Opens the online help.