To view Spanning
Tree Parameters:The STP Parameter screen is different for "STP per VLAN" and "STP per Device" with respect to the tabs.
For both STP types the following tabs are displayed:
General Parameters
Bridge Setup Parameters
Only for "STP per Device" the following tabs are presented:
Root Parameters
STP Setup Parameters
To view Spanning
Tree Parameters:
On the Menu Bar, click Bridge.
On the Device menu, point to Spanning Tree.
On the Spanning Tree menu, click Parameters. The General Parameters window is displayed with the relevant tabs.
The default opening screen is the General Parameters tab. The following paragraphs illustrate and describe each screen tab.
Defines general information about the STP on a device or VLAN, including the protocol specification, and port to VLAN designations. These parameters can be modified.
The General Parameters tab displays the following fields:
Global STP Status — Indicates whether STP should run on the device. This is a system-wide proprietary parameter disabled by default. The options are as follows:
Enabled — Enables STP
Disabled — Disables STP
STP Type — Indicates the mode of maintaining the STP database, per device or per VLAN.
STP Type After Reset — Indicates the STP setting after the device is reset. The device must be reset for the change to be implemented. The possible values are:
Per Device — Indicates that STP is per device.
Per VLAN — Indicates that STP is per VLAN.
Protocol Specification — Indicates the IEEE standard in use.
Must belong to VLAN — This parameter is relevant for per-device mode only. The values are as follows:
True (default) — Each port thats defined within a VLAN is participating in the STP.
False — All ports on the device participates in the STP.
Number Format — Defines whether the STP uses the extended port number format.
True (default) — Extended port number specified in IEEE 802.1t.
False — Standard port number specified in IEEE 802.1d.
The Bridge Setup Parameters tab displays the following fields:
Bridge Priority — The Bridge priority within the Spanning Tree. Identifies the bridge priority and is part of the bridge identifier. The bridge identifier is 8 octets long, and the two most significant octets indicate the bridge priority. The bridge with the lowest value has the highest priority and is the root
Bridge Max Age (sec) — Identifies the interval a bridge that waits for the receipt of a hello packet before initiating a topology change. It is the time interval that determines when to discard a Configuration Message (CM).
This parameter is configured on all the bridges participating in the STP but only the one belonging to the elected Root Bridge is used.
It is strongly recommended that: Max age is greater or equal to Hello time x 2 + 1.0s.
Bridge Hello Time (sec) — Identifies the interval of time between each CM sent by the Root Bridge. This interval between issuing CM is configured on all the bridges participating in the STP but is only relevant to the Root Bridge.
Note: Shortening the recommended 2-second period makes the protocol more robust, but the loss of CMs is high. Lengthening this time lowers the overhead of the algorithm (because the interval between transmission of CMs will be larger).
Bridge Forward Delay (sec) — Identifies the time interval a bridge waits (by being in the listening and learning states) before forwarding data packets. This parameter is configured on all the bridges participating in the STP. Only the parameter elected to the Root Bridge is used.
It is strongly recommended that: 2 x Bridge Forward Delay is greater or equal to Max age
The Root Parameters tab displays the following fields:
STP MIB Version — The installed MIB version.
Bridge Priority — The Bridge Priority value is used to define the choice of root and designated bridges. The bridge with the lowest value has the highest priority, and is the root. The value of this parameter is not learned from the network and is device specific.
Bridge Address — The value is part of a Bridge Identifier. This parameter is individual for each device and is not contained in CM. The STP requires that a single unique identifier (Bridge Identifier) be associated with each Bridge transmitting CMs.
Designated Root Priority — The Root Bridge priority within the Spanning Tree. This value is used as part of the Root Identifier parameter in all CMs originated by this node.
Designated Root Address — The Root Bridge MAC address within the Spanning Tree. This value is used as part of the Root Identifier parameter.
Root Path Cost — The cost of the path from this Bridge to the Root Bridge. This value is used as part of the Root Identifier parameter.
Root Port — The port number which offers the lowest cost path from this bridge to the Root Bridge. It is not significant when the Bridge is the Root, and is set to zero
Topology Change Time — The time (in seconds) since the last time a topology change was detected by the bridged community.
Topology Changes Count — The total number of topology changes detected by this bridge since the manageable bridged community was last reset or initialized.
The STP Setup Parameters tab displays the following fields:
Max Age (sec) — The maximum age of STP information learned from the network on any port before it is discarded, in seconds. Identifies the timeout value used by all Bridges. This ensures that each Bridge has a consistent value against which to test the age of stored configuration information.
Hello Time (sec) — Defines the time period to elapse between the transmission of CMs through a given port. This value is learned from the network
Hold Time (sec) — Defines the minimum time period to elapse between the transmission of CMs through a given port. At most, one CM shall be transmitted in any Hold Time period. This value is learned from the network.
Forward Delay (sec) — Identifies the timeout value to be used by all Bridges as learned from the network.
This time value measured in seconds, controls how fast a port changes its spanning state when moving towards the Forwarding State. The value determines how long the port stays in each of the Listening and Learning states, which precede the Forwarding State. This value is also used, when a topology change has been detected and is underway, to age all dynamic entries in the Forwarding Database.
The parameter ensures that each Bridge uses a consistent value for the Forward Delay Timer when changing the State of a Port to the Forwarding State.