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Configuring a Spanning Tree—Quick Configuration

Juniper devices provide Layer 2 loop prevention through Spanning Tree Protocol (STP), Rapid Spanning Tree Protocol (RSTP), and Multiple Spanning Tree Protocol (MSTP). You can configure bridge protocols data unit (BPDU) protection on interfaces to prevent them from receiving BPDUs that could result in STP misconfigurations, which could lead to network outages.

You can use the J-Web Quick Configuration to add a spanning tree or to edit or delete an existing spanning tree.

To access the Spanning Tree Quick Configuration:

In the J-Web user interface, select Configuration > Quick Configuration > Switching > Spanning Tree.
The Spanning Tree Configuration page displays a list of existing spanning trees. If you select a specific spanning tree, the specific spanning tree details are displayed in the General and Interfaces tabs.
Click one of the following:
- Add—Creates a spanning tree.
- Edit—Edits an existing spanning-tree configuration.
- Delete—Deletes an existing spanning tree.
When you are adding a spanning tree, select a protocol name:
- If you select STP, enter information as described in Table 2.
- If you select RSTP, enter information as described in Table 3.
- If you select MSTP, enter information as described in Table 4.
Select the Ports tab to configure the ports associated with this spanning tree. Click one of the following:
- Add—Creates a new spanning-tree interface configuration.
- Edit—Modifies an existing spanning-tree interface configuration.
- Delete—Deletes an existing spanning-tree interface configuration.
When you are adding or editing a spanning-tree port, enter information as described in Table 5.
Click one:
- To apply changes to the configuration, click OK.
- To cancel the configuration without saving changes, click Cancel.

Table 2: STP Configuration Parameters

Field	Function	Action
Protocol Name	Displays the spanning-tree protocol.	View only.
Disable	Disables STP on the interface.	To enable this option, select the check box.
BPDU Protect	Specifies that BPDU blocks are to be processed.	To enable this option, select the check box.
Bridge Priority	Specifies the bridge priority. The bridge priority determines which bridge is elected as the root bridge. If two bridges have the same path cost to the root bridge, the bridge priority determines which bridge becomes the designated bridge for a LAN segment.	Select a value.
Forward Delay	Specifies the number of seconds an interface waits before changing from spanning-tree learning and listening states to the forwarding state.	Enter a value from 4 through 30 seconds.
Hello Time	Specifies time interval in seconds at which the root bridge transmits configuration BPDUs.	Enter a value from 1 through 10 seconds.
Max Age	Specifies the maximum aging time in seconds for all MST instances. The maximum aging time is the number of seconds a switch waits without receiving spanning-tree configuration messages before attempting a reconfiguration.	Enter a value from 6 through 40 seconds.

Table 3: RSTP Configuration Parameters

Field	Function	Action
Protocol Name	Displays the spanning-tree protocol.	View only.
Disable	Specifies whether RSTP must be disabled on the interface.	To enable this option, select the check box.
BPDU Protect	Specifies that BPDU blocks are to be processed.	To enable this option, select the check box.
Bridge Priority	Specifies the bridge priority. The bridge priority determines which bridge is elected as the root bridge. If two bridges have the same path cost to the root bridge, the bridge priority determines which bridge becomes the designated bridge for a LAN segment.	Select a value.
Forward Delay	Specifies the number of seconds a port waits before changing from its spanning-tree learning and listening states to the forwarding state.	Enter a value from 4 through 30 seconds.
Hello Time	Specifies the hello time in seconds for all MST instances.	Enter a value from 1 through 10 seconds.
Max Age	Specifies the maximum aging time in seconds for all MST instances. The maximum aging time is the number of seconds a switch waits without receiving spanning-tree configuration messages before attempting a reconfiguration.	Enter a value from 6 through 40 seconds.

Table 4: MSTP Configuration Parameters

Field	Function	Action
Protocol Name	Displays the spanning-tree protocol.	View only.
Disable	Specifies whether MSTP must be disabled on the interface.	To enable this option, select the check box.
BPDU Protect	Specifies that BPDU blocks are to be processed.	To enable this option, select the check box.
Bridge Priority	Specifies the bridge priority. The bridge priority determines which bridge is elected as the root bridge. If two bridges have the same path cost to the root bridge, the bridge priority determines which bridge becomes the designated bridge for a LAN segment.	Select a value.
Forward Delay	Specifies the number of seconds a port waits before changing from its spanning-tree learning and listening states to the forwarding state.	Enter a value from 4 through 30 seconds.
Hello Time	Specifies the hello time in seconds for all MST instances.	Enter a value from 1 through 10 seconds.
Max Age	Specifies the maximum aging time for all MST instances. The maximum aging time is the number of seconds a switch waits without receiving spanning-tree configuration messages before attempting a reconfiguration.	Enter a value from 6 through 40 seconds.
Configuration Name	MSTP region name carried in the MSTP bridge protocol data units (BPDUs).	Enter a name.
Max Hops	Maximum number of hops a BPDU can be forwarded in the MSTP region	Enter a value from 1 through 255.
Revision Level	Revision number of the MSTP region configuration.	Enter a value from 0 through 65535.
MSTI tab
MSTI Id	Specifies the multiple spanning-tree instance (MSTI) identifier. MSTI IDs are local to each region, so you can reuse the same MSTI ID in different regions.	Click one: Add—Creates a MSTI. Edit—Edits an existing MSTI. Delete—Deletes an existing MSTI.
Bridge Priority	Specifies the bridge priority. The bridge priority determines which bridge is elected as the root bridge. If two bridges have the same path cost to the root bridge, the bridge priority determines which bridge becomes the designated bridge for a LAN segment.	Select a value.
VLAN	Specifies the VLANs for the MSTI.	Click one: Add—Selects VLANs from the list. Remove—Deletes the selected VLAN.
Interfaces	Specifies the interface for the MSTP protocol.	Click one: Add—Selects interfaces from the list. Edit—Edits the selected interface. Remove—Deletes the selected interface.

Table 5: Spanning-Tree Ports Configuration Details

Field	Function	Action
Interface Name	Specifies the interface for the spanning-tree protocol type.	Select an interface.
Cost	Specifies the link cost to control which bridge is the designated bridge and which interface is the designated interface.	Enter a value from 1 through 200,000,000.
Priority	Specifies the interface priority to control which interface is elected as the root port.	Select a value.
Disable Port	Disables the spanning-tree protocol type on the interface.	Select to disable the spanning-tree protocol type.
Edge	Configures the interface as an edge interface. Edge interfaces immediately transition to a forwarding state.	Select to configure the interface as an edge interface.
No Root Port	Specifies an interface as a spanning-tree designated port. If the bridge receives superior STP bridge protocol data units (BPDUs) on a root-protected interface, that interface transitions to a root-prevented STP state (inconsistency state) and the interface is blocked. This blocking prevents a bridge that should not be the root bridge from being elected the root bridge. When the bridge stops receiving superior STP BPDUs on the root-protected interface, interface traffic is no longer blocked.	Select to configure the interface as a spanning-tree designated port.
Interface Mode	Specifies the link mode.	Select one: Point to Point—For full-duplex links, select this mode. Shared—For half-duplex links, select this mode.
BPDU Timeout Action	Specifies the BPDU timeout action for the interface.	Select one: Alarm—Generate a system log file message to record the loop protection event. Block—Configure loop protection on a specific interface.

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