Cisco Sg3008 Manual
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Spanning Tree Configuring Rapid Spanning Tree Settings 236 Cisco Small Business 200, 300 and 500 Series Managed Switch Administration Guide (Internal Version) 14 -Blocking—The port is currently blocked, and cannot forward traffic (with the exception of BPDU data) or learn MAC addresses. -Listening—The port is in Listening mode. The port cannot forward traffic, and cannot learn MAC addresses. -Learning—The port is in Learning mode. The port cannot forward traffic, but it can learn new MAC addresses. -For warding—The port is in Forwarding mode. The port can forward traffic and learn new MAC addresses. •Designated Bridge ID—Displays the bridge priority and the MAC address of the designated bridge. •Designated Port ID—Displays the priority and interface of the selected port. •Designated Cost—Displays the cost of the port participating in the STP topology. Ports with a lower cost are less likely to be blocked if STP detects loops. •Forward Transitions—Displays the number of times the port has changed from the Blocking state to Forwarding state. •Speed—Displays the speed of the port. •LAG—Displays the LAG to which the port belongs. If a port is a member of a LAG, the LAG settings override the port settings. STEP 4Click Apply. The interface settings are written to the Running Configuration file. Configuring Rapid Spanning Tree Settings Rapid Spanning Tree Protocol (RSTP) enables a faster STP convergence without creating forwarding loops. The RSTP Interface Settings page enables you to configure RSTP per port. Any configuration that is done on this page is active when the global STP mode is set to RSTP or MSTP.
Spanning Tree Configuring Rapid Spanning Tree Settings Cisco Small Business 200, 300 and 500 Series Managed Switch Administration Guide (Internal Version) 237 14 To enter RSTP settings: STEP 1Click Spanning Tree > STP Status and Global Settings. Enable RSTP. STEP 2Click Spanning Tree > RSTP Interface Settings. The RSTP Interface Settings page appears: STEP 3Select a port. NOTEActivate Protocol Migration is only available after selecting the port that is connected to the bridge partner being tested. STEP 4If a link partner is discovered by using STP, click Activate Protocol Migration to run a Protocol Migration test. This discovers whether the link partner using STP still exists, and if so whether it has migrated to RSTP or MSTP. If it still exists as an STP link, the device continues to communicate with it by using STP. Otherwise, if it has been migrated to RSTP or MSTP, the device communicates with it using RSTP or MSTP, respectively. STEP 5Select an interface, and click Edit. STEP 6Enter the parameters: •Interface—Set the interface, and specify the port or LAG where RSTP is to be configured. •Point to Point Administrative Status—Define the point-to-point link status. Ports defined as Full Duplex are considered Point-to-Point port links. - Enable—This port is an RSTP edge port when this feature is enabled, and is brought to Forwarding mode quickly (usually within 2 seconds). - Disable—The port is not considered point-to-point for RSTP purposes, which means that STP works on it at regular speed, as opposed to high speed. - Auto—Automatically determines the device status by using RSTP BPDUs. •Point to Point Operational Status—Displays the Point-to-Point operational status if the Point to Point Administrative Status is set to Auto. •Role—Displays the role of the port that was assigned by STP to provide STP paths. The possible roles are: - Root—Lowest cost path to forward packets to the Root Bridge.
Spanning Tree Configuring Rapid Spanning Tree Settings 238 Cisco Small Business 200, 300 and 500 Series Managed Switch Administration Guide (Internal Version) 14 -Designated—The interface through which the bridge is connected to the LAN, which provides the lowest cost path from the LAN to the Root Bridge. - Alternate—Provides an alternate path to the Root Bridge from the root interface. - Backup—Provides a backup path to the designated port path toward the Spanning Tree leaves. This provides a configuration in which two ports are connected in a loop by a point-to-point link. Backup ports are also used when a LAN has two or more established connections to a shared segment. - Disabled—The port is not participating in Spanning Tree. •Mode—Displays the current Spanning Tree mode: Classic STP or RSTP. •Fast Link Operational Status—Displays whether the Fast Link (Edge Port) is enabled, disabled, or automatic for the interface. The values are: - Enabled—Fast Link is enabled. - Disabled—Fast Link is disabled. - Auto—Fast Link mode is enabled a few seconds after the interface becomes active. •Port Status—Displays the RSTP status on the specific port. - Disabled—STP is currently disabled on the port. - Blocking—The port is currently blocked, and it cannot forward traffic or learn MAC addresses. - Listening—The port is in Listening mode. The port cannot forward traffic, and cannot learn MAC addresses. - Learning—The port is in Learning mode. The port cannot forward traffic, however it can learn new MAC addresses. - For warding—The port is in Forwarding mode. The port can forward traffic and learn new MAC addresses. STEP 7Click Apply. The Running Configuration file is updated.
Spanning Tree Multiple Spanning Tree Cisco Small Business 200, 300 and 500 Series Managed Switch Administration Guide (Internal Version) 239 14 Multiple Spanning Tree Multiple Spanning Tree Protocol (MSTP) is used to separate the STP port state between various domains (on different VLANs). For example, while port A is blocked in one STP instance due to a loop on VLAN A, the same port can be placed in the Forwarding State in another STP instance. The MSTP Properties page enables you to define the global MSTP settings. To configure MSTP: 1. Set the STP Operation Mode to MSTP as described in the Configuring STP Status and Global Settings page. 2. Define MSTP instances. Each MSTP instance calculates and builds a loop free topology to bridge packets from the VLANs that map to the instance. Refer to the Mapping VLANs to a MSTP Instance section. 3. Decide which MSTP instance be active in what VLAN, and associate these MSTP instances to VLAN(s) accordingly. 4. Configure the MSTP attributes by: •Defining MSTP Properties •Defining MSTP Instance Settings •Mapping VLANs to a MSTP Instance Defining MSTP Properties The global MSTP configures a separate Spanning Tree for each VLAN group and blocks all but one of the possible alternate paths within each spanning tree instance. MSTP enables formation of MST regions that can run multiple MST instances (MSTI). Multiple regions and other STP bridges are interconnected using one single common spanning tree (CST). MSTP is fully compatible with RSTP bridges, in that an MSTP BPDU can be interpreted by an RSTP bridge as an RSTP BPDU. This not only enables compatibility with RSTP bridges without configuration changes, but also causes any RSTP bridges outside of an MSTP region to see the region as a single RSTP bridge, regardless of the number of MSTP bridges inside the region itself. For two or more switches to be in the same MST region, they must have the same VLANs to MST instance mapping, the same configuration revision number, and the same region name.
Spanning Tree Mapping VL ANs to a MSTP Instance 240 Cisco Small Business 200, 300 and 500 Series Managed Switch Administration Guide (Internal Version) 14 Switches intended to be in the same MST region are never separated by switches from another MST region. If they are separated, the region becomes two separate regions. This mapping can be done in the VLAN to MST Instance page. Use this page if the system operates in MSTP mode. To d e f i n e M S T P : STEP 1Click Spanning Tree > STP Status and Global Settings. Enable MSTP. STEP 2Click Spanning Tree > MSTP Properties. STEP 3Enter the parameters. •Region Name—Define an MSTP region name. •Revision—Define an unsigned 16-bit number that identifies the revision of the current MST configuration. The field range is from 0 to 65535. •Max Hops—Set the total number of hops that occur in a specific region before the BPDU is discarded. Once the BPDU is discarded, the port information is aged out. The field range is from 1 to 40. •IST Master—Displays the regions master. STEP 4Click Apply. The MSTP properties are defined, and the Running Configuration file is updated. Mapping VLANs to a MSTP Instance The VLAN to MSTP Instance page enables you to map each VLAN to a Multiple Spanning Tree Instance (MSTI). For devices to be in the same region, they must have the same mapping of VLANs to MSTIs. NOTEThe same MSTI can be mapped to more than one VLAN, but each VLAN can only have one MST Instance attached to it. Configuration on this page (and all of the MSTP pages) applies if the system STP mode is MSTP. Up to seven MST instances (predefined from 1-7) can be defined on 300 Series switches, in addition to instance zero.
Spanning Tree Defining MSTP Instance Settings Cisco Small Business 200, 300 and 500 Series Managed Switch Administration Guide (Internal Version) 241 14 For those VLANs that are not explicitly mapped to one of the MST instances, the device automatically maps them to the CIST (Core and Internal Spanning Tree) instance. The CIST instance is MST instance 0. To map VLANs to MST Instances: STEP 1Click Spanning Tree > VLAN to MSTP Instance. The VLAN to MSTP Instance page contains the following fields: •MST Instance ID—All MST instances are displayed. •VLANs—All VLANs belonging to the MST instance are displayed. STEP 2To add a VLAN to an MSTP instance, select the MST instance, and click Edit. STEP 3Enter the parameters. •MST Instance ID—Select the MST instance. •VLANs—Define the VLANs being mapped to this MST instance. •Action—Define whether to Add (map) the VLAN to the MST instance or Remove it. STEP 4Click Apply. The MSTP VLAN mappings are defined, and the Running Configuration file is updated. Defining MSTP Instance Settings The MSTP Instance Settings page enables you to configure and view parameters per MST instance. This is the per-instance equivalent to the Configuring STP Status and Global Settings. To enter MSTP instance settings: STEP 1Click Spanning Tree > MSTP Instance Settings. STEP 2Enter the parameters. •Instance ID—Select an MST instance to be displayed and defined.
Spanning Tree Defining MSTP Interface Settings 242 Cisco Small Business 200, 300 and 500 Series Managed Switch Administration Guide (Internal Version) 14 •Included VLAN—Displays the VLANs mapped to the selected instance. The default mapping is that all VLANs are mapped to the common and internal spanning tree (CIST) instance 0). •Bridge Priority—Set the priority of this bridge for the selected MST instance. •Designated Root Bridge ID—Displays the priority and MAC address of the Root Bridge for the MST instance. •Root Port—Displays the root port of the selected instance. •Root Path Cost—Displays the root path cost of the selected instance. •Bridge ID—Displays the bridge priority and the MAC address of this device for the s ele cte d instanc e. •Remaining Hops—Displays the number of hops remaining to the next destination. STEP 3Click Apply. The MST Instance configuration is defined, and the Running Configuration file is updated. Defining MSTP Interface Settings The MSTP Interface Settings page enables you to configure the port MSTP settings for every MST instance, and to view information that has currently been learned by the protocol, such as the designated bridge per MST instance. To configure the ports in an MST instance: STEP 1Click Spanning Tree > MSTP Interface Settings. STEP 2Enter the parameters. •Instance equals To—Select the MSTP instance to be configured. •Interface Type equals to—Select whether to display the list of ports or LAGs. STEP 3Click Go. The MSTP parameters for the interfaces on the instance are displayed. STEP 4Select an interface, and click Edit.
Spanning Tree Defining MSTP Interface Settings Cisco Small Business 200, 300 and 500 Series Managed Switch Administration Guide (Internal Version) 243 14 STEP 5Enter the parameters. •Instance ID—Select the MST instance to be configured. •Interface—Select the interface for which the MSTI settings are to be defined. •Interface Priority—Set the port priority for the specified interface and MST instance. •Path Cost—Enter the port contribution to the root path cost in the User Defined textbox or select Use Default to use the default value. •Port State—Displays the MSTP status of the specific port on a specific MST instance. The parameters are defined as: -Disabled—STP is currently disabled. -Blocking—The port on this instance is currently blocked, and cannot forward traffic (with the exception of BPDU data) or learn MAC addresses. -Listening—The port on this instance is in Listening mode. The port cannot forward traffic, and cannot learn MAC addresses. -Learning—The port on this instance is in Learning mode. The port cannot forward traffic, but it can learn new MAC addresses. -For warding—The port on this instance is in Forwarding mode. The port can forward traffic and learn new MAC addresses. - Boundary—The port on this instance is a boundary port. It inherits its state from instance 0 and can be viewed on the STP Interface Settings page. •Port Role—Displays the port or LAG role, per port or LAG per instance, assigned by the MSTP algorithm to provide STP paths: -Root—Forwarding packets through this interface provides the lowest cost path for forwarding packets to the root device. -Designated—The interface through which the bridge is connected to the LAN, which provides the lowest root path cost from the LAN to the Root Bridge for the MST instance. -Alternate—The interface provides an alternate path to the root device from the root interface.
Spanning Tree Defining MSTP Interface Settings 244 Cisco Small Business 200, 300 and 500 Series Managed Switch Administration Guide (Internal Version) 14 -Backup—The interface provides a backup path to the designated port path toward the Spanning Tree leaves. Backup ports occur when two ports are connected in a loop by a point-to-point link. Backup ports also occur when a LAN has two or more established connections to a shared segment. -Disabled—The interface does not participate in the Spanning Tree. - Boundary—The port on this instance is a boundary port. It inherits its state from instance 0 and can be viewed on the STP Interface Settings page. •Mode—Displays the current interface Spanning Tree mode. -If the link partner is using MSTP or RSTP, the displayed port mode is RSTP. -If the link partner is using STP, the displayed port mode is STP. •Type—Displays the MST type of the port. -Boundary—A Boundary port attaches MST bridges to a LAN in a remote region. If the port is a boundary port, it also indicates whether the device on the other side of the link is working in RSTP or STP mode. -Internal—The port is an internal port. •Designated Bridge ID—Displays the ID number of the bridge that connects the link or shared LAN to the root. •Designated Port ID—Displays the Port ID number on the designated bridge that connects the link or the shared LAN to the root. •Designated Cost—Displays the cost of the port participating in the STP topology. Ports with a lower cost are less likely to be blocked if STP detects loops. •Remain Hops—Displays the hops remaining to the next destination. •Forward Transitions—Displays the number of times the port has changed from the Forwarding state to the Blocking state. STEP 6Click Apply. The Running Configuration file is updated.
Spanning Tree Defining MSTP Interface Settings Cisco Small Business 200, 300 and 500 Series Managed Switch Administration Guide (Internal Version) 245 14