Configure Spanning Tree Protocol (STP) Status and Global Settings on ESW2-550X Switches

Objective

Spanning-Tree Protocol (STP) prevents loops from being formed when switches or bridges are interconnected via multiple paths. Spanning-Tree Protocol implements the 802.1D IEEE algorithm by exchanging Bridge Protocol Data Unit (BPDU) messages with other switches to detect loops, and then removes the loop by shutting down selected bridge interfaces. This algorithm guarantees that there is one and only one active path between two network devices. The Cisco ESW2-550X Stackable Managed Switches are stackable managed Ethernet switches. These switches provide 48 ports of Gigabit Ethernet connectivity with 10 Gigabit uplinks.

The objective of this article is to explain how to configure STP status and global settings on ESW2-550X Stackable Managed Switches.

Applicable Devices

• ESW2-550X
• ESW2-550X-DC

Software Version

• v1.2.9.44

STP Status and Global Settings Configuration

Step 1. Log in to the web configuration utility and choose Spanning Tree > STP Status & Global Settings. The STP Status & Global Settings page opens:

Global Settings Configuration

Step 1. Check the Enable check box in the Spanning Tree State field to enable STP.

Step 2. Click the specific radio button to choose the desired STP Operating Mode.

• Classic STP — Provides a single path between any two end stations which avoids and eliminates loops.

• Rapid STP — Detects network topologies to provide faster convergence of the spanning tree. This is most effective when the network topology is naturally tree-structured, and therefore faster convergence might be possible.

• Multiple STP — Detects Layer 2 loops, and attempts to mitigate them by preventing the involved port from transmitting traffic. MSTP enables several STP instances, so that it is possible to detect and mitigate loops separately in each instance. MSTP provides full connectivity for packets allocated to any VLAN. In addition, MSTP transmits packets assigned to various VLANs through different multiple spanning tree (MST) regions. 

Step 3.  Click the desired radio button in the Bridge Protocol Data Unit (BPDU) Handling field. BPDU is used to transmit spanning tree information when STP is disabled on the port or the switch. 

• Filtering — Filters BPDU packets when spanning tree is disabled on an interface.

• Flooding — Floods BPDU packets when spanning tree is disabled on an interface.

Step 4. Click the desired radio button in the Path Cost Default Values field. This is used to assign default path costs to the STP ports.

• Short — Specifies the range 1 through 65,535 for port path costs.

• Long — Specifies the range 1 through 200,000,000 for port path costs.

Step 5. Click Apply.

Bridge Settings Configuration

Step 1. Enter the priority value in the Priority field. After the exchange of BPDUs, the device with the lowest priority becomes the Root Bridge. Root Bridge is the bridge which becomes the active bridge of the network and is in charge of all the other decisions, such as which port needs to be blocked and which port needs to be in the forward mode. In the case that all bridges use the same priority, then their MAC addresses are used to determine which one is the Root Bridge. The bridge priority value is provided in increments of 4096.

Step 2. Enter the hello time in the Hello Time field. This is the interval in seconds that a root bridge waits between configuration messages.

Step 3. Enter the maximum age in the Max Age field. This is the interval in seconds that the switch waits without receiving a configuration message before the switch makes an attempt to redefine its own configuration.

Step 4. Enter the forward delay in the Forward Delay field. This is the interval in seconds that a bridge remains in a learning state before forwarding packets.

Step 5. Click Apply.

Designated Root Status

The following information is displayed in the Designated Root area:

• Bridge ID — The bridge priority concatenated with the MAC address of the switch.

• Root Bridge ID — The Root Bridge priority concatenated with the MAC address of the Root Bridge.

• Root Port — The port that offers the lowest cost path from this bridge to the Root Bridge. 

• Root Path Cost — The cost of the path from this bridge to the root.

• Topology Changes Counts — The total number of STP topology changes that have occurred.

• Last Topology Change — The time interval that elapsed since the last topology change occurred. The time is displayed in days/hours/minutes/seconds format.