# Spanning Tree

## Purpose

NOTE: The Spanning Tree form is not applicable to MiVoice Business for Industry Standard Servers (ISS).

This form is used to configure Rapid Spanning Tree Protocol (RSTP) parameters on the CXi II, MXe III and AX controllers. The STP parameters are factory-programmed and non-editable.

For basic installations, the RSTP parameters should be left at the factory default settings. More complex installations may require custom settings to achieve optimum network performance.

You can configure RSTP attributes for specific CXi II, MXe III, and AX L2 ports, including port priority, path cost, link type, and edge port. You may use a different priority or path cost for ports of the same media type to indicate the preferred path; link type to indicate a point-to-point connection or shared-media connection; and edge port to indicate that the attached device is a computer or other end-node device.

CAUTIONS:

- Enabling Spanning Tree Protocol causes the Layer 2 switch to temporarily drop all IP packets. To minimize interruptions in service, enable STP/RSTP at low traffic or off-hour times only. Mitel recommends that you check with your Information Technology department before enabling STP/RSTP.

- Poorly chosen adjustments to the spanning tree parameters can have a negative impact on network performance. You are advised to change the parameters only if you are familiar with spanning tree configuration and have determined that adjustments are necessary. Please refer to the MiVoice Business Engineering Guidelines and Resiliency Guidelines for guidance.

Use this form when performing the following tasks:

- Set Up Your System

## Field Descriptions

Parameter | Description | Default Value
Parameter | Description | Default Value
Spanning Tree Bridge
Spanning Tree (STP) Enabled | Existing 700-user Controllers (including the 250-user variant) only. Select "Yes" to enable Spanning Tree Protocol ( STP) on the controller's built-in Layer 2 switch. Only enable this setting when the controller is on an STP-enabled network. When enabled, the controller uses STP configuration values specified as defaults in the IEEE 802.1D specification. The form shows some of the values as protected (read-only) fields; see STP Default Settings for the others. Note: Spanning Tree can also be enabled/disabled on the System Options form. | No (disabled)
Rapid Spanning Tree (RSTP) | CXi II, MXe III, and AX only. Select "Enabled" to enable Rapid Spanning Tree Protocol. (Only enable this setting when the controller is on an STP-enabled network.) | Disabled
Bridge Priority | Enter the Spanning Tree Bridge priority. The priority is a step value of 0-15 which results in a multiple of 4096 (0x1000) from zero to fifteen (0-15). A higher value means lower priority and less chance of becoming the Root Bridge in the Spanning Tree network. NOTE: MiVoice Business should not be used as the root bridge or root switch. To guard against this occurring MiVoice Business is factory programmed with the highest possible value for Bridge Priority. | 15 (61440)
Force Version | CXi II, MXe III, and AX only. Select the format (STP or RSTP) in which to send BPDU (Bridge Protocol Data Unit) A spanning tree protocol (STP) message unit that describes the attributes of a switch port such as its MAC address, priority and cost to reach. BPDUs enable switches that participate in a spanning tree protocol to gather information about each other. messages on all L2 ports. "STP-compatible" sends only STP (or legacy) BDPUs. "RSTP" sends RSTP BPDUs unless a legacy port is detected, in which case STP BPDUs are sent instead. | RSTP
Hello Time (seconds) | System-generated, protected field. Applies only to the root bridge/switch. Hello Time is the interval between transmission of Bridge Protocol Data Unit (BPDU) messages by the root bridge/switch. The time the 802.1D standard two seconds. |
Max Age (seconds) | System-generated, protected field. Applies only to the Root Bridge or Root Switch. Max Age is the maximum time (in seconds) that the L2 switch can wait without receiving a configuration message before attempting to change the spanning tree topology. The time the 802.1D standard 20 seconds. |
Forward Delay (seconds) | System-generated, protected field. The amount of time the L2 switch waits (the listen and learn period) before beginning to forward data packets. |
Tx Hold Count (seconds) | System-generated, protected field for CXi II, MXe III, and AX only. The number of BPDUs that can be transmitted per Hello Interval. The count is the 802.1D standard six. |
Spanning Tree Port (CXi II, MXe III, and AX)
Port | System-generated, protected field. Indicates the number of the port. The default database has 17 entries with default values for the CXi II two entries with default values for the MXe III two entries with default values for the AX. The first 16 CXi II entries are for the powered 10/100Base-T/TX LAN ports. The 17th entry for the CXi II is for the unpowered 10/100/1GBase-T LAN port(s). The entries for the MXeIII are for the unpowered 10/100/1GBase-T LAN port(s). The two entries for the AX are for the unpowered 10/100 Base-T LAN port(s). |
Path Cost | Enter a cost for the port in the range 1 to 200,000,000 or zero for Auto. The Auto setting automatically determines cost by the port type (10 Mbit/s, 100 Mbit/s or 1 Gbit/s) as follows: 10 Mbit/s – 2,000,000 100 Mbit/s – 200,000 1 Gbit/s – 20,000 | Auto
Priority | Enter a value to specify the preference given to this port relative to others for forwarding traffic out of the topology. The priority is a step value of 0-15 which results in a multiple of of 16 (0x10) from zero to fifteen (0-15). A higher value means lower priority. | 8 [128]
Edge | System-generated, protected field for CXi II, MXe III, and AX only. Select "Yes" if the port is connected to a computer or other end-node device that is not considered in spanning tree calculations. The default on the CXi II is "Yes" for ports 1-16 and "No" on port 17. On the MXe III and AX the default is "No." NOTE: The RSTP protocol can auto-detect an Edge port and a non-edge port. It is recommended that Edge ports are configured explicitly to take advantage of the Edge port feature, instead of allowing the protocol to auto-detect them. |
Point-to-Point | System-generated, protected field. Shows the link type connected to the port: "Force-True" indicates that the port is connected to shared media such as a hub. "Force-False" indicates that the port is connected to another bridge, switch, or and end node. "Auto" indicates that the state is either Force-True or Force-False depending on whether or not the link is full duplex. |