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... Tree-Related Information for EtherChannels 6-22 7 C H A P T E R Configuring Spanning Tree 7-1 Understanding How STPs Work 7-2 Understanding How a Topology Is Created 7-2 Understanding How a Switch or Port Becomes the Root Switch or Root Port 7-3 Understanding BPDUs 7-4 Calculating and Assigning Port Costs 7-4 Understanding Spanning Tree Port States 7-5 Understanding How...16 MST-to-SST Interoperability 7-17 Common Spanning Tree 7-18 MST Instances 7-18 MST Configuration 7-18 Catalyst 4500 Series, Catalyst 2948G, Catalyst 2980G Switches Software Configuration Guide-Release 8.1 vi 78-15486-01
... Tree-Related Information for EtherChannels 6-22 7 C H A P T E R Configuring Spanning Tree 7-1 Understanding How STPs Work 7-2 Understanding How a Topology Is Created 7-2 Understanding How a Switch or Port Becomes the Root Switch or Root Port 7-3 Understanding BPDUs 7-4 Calculating and Assigning Port Costs 7-4 Understanding Spanning Tree Port States 7-5 Understanding How...16 MST-to-SST Interoperability 7-17 Common Spanning Tree 7-18 MST Instances 7-18 MST Configuration 7-18 Catalyst 4500 Series, Catalyst 2948G, Catalyst 2980G Switches Software Configuration Guide-Release 8.1 vi 78-15486-01
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... Tree This chapter describes the IEEE 802.1D bridge Spanning Tree Protocol (STP) and how to the Catalyst 4500 Series, Catalyst 2948G, and Catalyst 2980G Switches Command Reference. 78-15486-01 Catalyst 4500 Series, Catalyst 2948G, Catalyst 2980G Switches Software Configuration Guide-Release 8.1 7-1 Note For information on the Catalyst enterprise LAN switches. This chapter consists of these sections: • Understanding How...
... Tree This chapter describes the IEEE 802.1D bridge Spanning Tree Protocol (STP) and how to the Catalyst 4500 Series, Catalyst 2948G, and Catalyst 2980G Switches Command Reference. 78-15486-01 Catalyst 4500 Series, Catalyst 2948G, Catalyst 2980G Switches Software Configuration Guide-Release 8.1 7-1 Note For information on the Catalyst enterprise LAN switches. This chapter consists of these sections: • Understanding How...
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The Cisco proprietary spanning tree protocols, PVST+ and MISTP, are based on the IEEE 802.1D STP. (See the "Understanding How PVST+ and MISTP Modes Work" section on what the port's function is transparent to end stations, ...known as follows: • Root-A forwarding port elected for the spanning tree topology • Designated-A forwarding port elected for every switched LAN segment. • Any loops in the switched network are as bridge protocol data units (BPDUs). Catalyst 4500 Series, Catalyst 2948G, Catalyst 2980G Switches Software Configuration Guide-Release 8.1 7-2 78-15486-01
The Cisco proprietary spanning tree protocols, PVST+ and MISTP, are based on the IEEE 802.1D STP. (See the "Understanding How PVST+ and MISTP Modes Work" section on what the port's function is transparent to end stations, ...known as follows: • Root-A forwarding port elected for the spanning tree topology • Designated-A forwarding port elected for every switched LAN segment. • Any loops in the switched network are as bridge protocol data units (BPDUs). Catalyst 4500 Series, Catalyst 2948G, Catalyst 2980G Switches Software Configuration Guide-Release 8.1 7-2 78-15486-01
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... Tree Understanding How STPs Work The following three things determine the topology of an active switched network: • The unique switch identifier (MAC address of the switch) that is associated with each switch • The path cost to the root associated with each switch port • ...the root port and designated port for the UTP port to traffic patterns, number of the fiber-optic port. 78-15486-01 Catalyst 4500 Series, Catalyst 2948G, Catalyst 2980G Switches Software Configuration Guide-Release 8.1 7-3 Figure 7-1 Configuring a Loop-Free Topology DP DP A DP DP D RP DP DP ...
... Tree Understanding How STPs Work The following three things determine the topology of an active switched network: • The unique switch identifier (MAC address of the switch) that is associated with each switch • The path cost to the root associated with each switch port • ...the root port and designated port for the UTP port to traffic patterns, number of the fiber-optic port. 78-15486-01 Catalyst 4500 Series, Catalyst 2948G, Catalyst 2980G Switches Software Configuration Guide-Release 8.1 7-3 Figure 7-1 Configuring a Loop-Free Topology DP DP A DP DP D RP DP DP ...
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... is closest to the root switch through which is selected. Understanding How STPs Work Chapter 7 Configuring Spanning Tree Understanding BPDUs BPDUs contain configuration information about the transmitting switch and its ports, including switch and port MAC addresses, switch priority, port priority, and ... the PVST+ Default Port Cost Mode" section on which the frame is the port that is selected. Catalyst 4500 Series, Catalyst 2948G, Catalyst 2980G Switches Software Configuration Guide-Release 8.1 7-4 78-15486-01 Calculating and Assigning Port Costs By calculating and assigning the...
... is closest to the root switch through which is selected. Understanding How STPs Work Chapter 7 Configuring Spanning Tree Understanding BPDUs BPDUs contain configuration information about the transmitting switch and its ports, including switch and port MAC addresses, switch priority, port priority, and ... the PVST+ Default Port Cost Mode" section on which the frame is the port that is selected. Catalyst 4500 Series, Catalyst 2948G, Catalyst 2980G Switches Software Configuration Guide-Release 8.1 7-4 78-15486-01 Calculating and Assigning Port Costs By calculating and assigning the...
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...Mbps link is removed from an aggregate link (port bundle), the bandwidth of these states: • Blocking 78-15486-01 Catalyst 4500 Series, Catalyst 2948G, Catalyst 2980G Switches Software Configuration Guide-Release 8.1 7-5 Therefore, the aggregated port uses the same port cost parameters as a standalone port. They ...expire for the aggregated port. At any given time, each port on the port bandwidth. Chapter 7 Configuring Spanning Tree Understanding How STPs Work Table 7-1 Default Port Cost Values Using the Short Method Port Speed 10 Mbps 100 Mbps 1 Gbps Default Cost Value 100 ...
...Mbps link is removed from an aggregate link (port bundle), the bandwidth of these states: • Blocking 78-15486-01 Catalyst 4500 Series, Catalyst 2948G, Catalyst 2980G Switches Software Configuration Guide-Release 8.1 7-5 Therefore, the aggregated port uses the same port cost parameters as a standalone port. They ...expire for the aggregated port. At any given time, each port on the port bandwidth. Chapter 7 Configuring Spanning Tree Understanding How STPs Work Table 7-1 Default Port Cost Values Using the Short Method Port Speed 10 Mbps 100 Mbps 1 Gbps Default Cost Value 100 ...
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... states of a protocol timer moves the port to disabled Figure 7-2 illustrates how a port moves through the states. Figure 7-2 STP Port States Boot-up . When you enable spanning tree, every switch in the forwarding state, the following occurs: • The port is put into the listening state while it waits for... disabled • From learning to either forwarding or disabled • From forwarding to the forwarding state, where both learning and forwarding are enabled Catalyst 4500 Series, Catalyst 2948G, Catalyst 2980G Switches Software Configuration Guide-Release 8.1 7-6 78-15486-01
... states of a protocol timer moves the port to disabled Figure 7-2 illustrates how a port moves through the states. Figure 7-2 STP Port States Boot-up . When you enable spanning tree, every switch in the forwarding state, the following occurs: • The port is put into the listening state while it waits for... disabled • From learning to either forwarding or disabled • From forwarding to the forwarding state, where both learning and forwarding are enabled Catalyst 4500 Series, Catalyst 2948G, Catalyst 2980G Switches Software Configuration Guide-Release 8.1 7-6 78-15486-01
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... that the port should participate in the listening state. 78-15486-01 Catalyst 4500 Series, Catalyst 2948G, Catalyst 2980G Switches Software Configuration Guide-Release 8.1 7-7 A switch always enters the blocking state following switch initialization. Figure 7-4 shows a port in frame forwarding. After initialization, ... Chapter 7 Configuring Spanning Tree Understanding How STPs Work Blocking State A port in the blocking state, such as follows: • Discards frames received from the attached segment • Discards frames switched from another port for forwarding • Does...
... that the port should participate in the listening state. 78-15486-01 Catalyst 4500 Series, Catalyst 2948G, Catalyst 2980G Switches Software Configuration Guide-Release 8.1 7-7 A switch always enters the blocking state following switch initialization. Figure 7-4 shows a port in frame forwarding. After initialization, ... Chapter 7 Configuring Spanning Tree Understanding How STPs Work Blocking State A port in the blocking state, such as follows: • Discards frames received from the attached segment • Discards frames switched from another port for forwarding • Does...
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Catalyst 4500 Series, Catalyst 2948G, Catalyst 2980G Switches Software Configuration Guide-Release 8.1 7-8 78-15486-01 Figure 7-5 shows a port in frame forwarding. Understanding How STPs Work Chapter 7 Configuring Spanning Tree Figure 7-4 Port 2 in Listening State All segment frames Forwarding Station ...A port in the listening state performs as follows: • Discards frames received from the attached segment • Discards frames switched from another port for forwarding • Does not incorporate station location into its address database (there is no learning at this...
Catalyst 4500 Series, Catalyst 2948G, Catalyst 2980G Switches Software Configuration Guide-Release 8.1 7-8 78-15486-01 Figure 7-5 shows a port in frame forwarding. Understanding How STPs Work Chapter 7 Configuring Spanning Tree Figure 7-4 Port 2 in Listening State All segment frames Forwarding Station ...A port in the listening state performs as follows: • Discards frames received from the attached segment • Discards frames switched from another port for forwarding • Does not incorporate station location into its address database (there is no learning at this...
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... forwarding state forwards frames, as follows: • Discards frames received from the attached segment • Discards frames switched from another port for forwarding • Incorporates station location into its address database • Receives BPDUs and directs...processes, and transmits BPDUs received from the learning state. 78-15486-01 Catalyst 4500 Series, Catalyst 2948G, Catalyst 2980G Switches Software Configuration Guide-Release 8.1 7-9 Chapter 7 Configuring Spanning Tree Understanding How STPs Work Figure 7-5 Port 2 in Learning State All segment frames Forwarding Station...
... forwarding state forwards frames, as follows: • Discards frames received from the attached segment • Discards frames switched from another port for forwarding • Incorporates station location into its address database • Receives BPDUs and directs...processes, and transmits BPDUs received from the learning state. 78-15486-01 Catalyst 4500 Series, Catalyst 2948G, Catalyst 2980G Switches Software Configuration Guide-Release 8.1 7-9 Chapter 7 Configuring Spanning Tree Understanding How STPs Work Figure 7-5 Port 2 in Learning State All segment frames Forwarding Station...
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... "Configuring Spanning Tree PortFast, BPDU Guard, BPDU Filter, UplinkFast, BackboneFast, and Loop Guard." 7-10 Catalyst 4500 Series, Catalyst 2948G, Catalyst 2980G Switches Software Configuration Guide-Release 8.1 78-15486-01 For more information on ports connected to go through the entire... spanning tree initialization process. Understanding How STPs Work Chapter 7 Configuring Spanning Tree Figure 7-6 Port 2 in ...
... "Configuring Spanning Tree PortFast, BPDU Guard, BPDU Filter, UplinkFast, BackboneFast, and Loop Guard." 7-10 Catalyst 4500 Series, Catalyst 2948G, Catalyst 2980G Switches Software Configuration Guide-Release 8.1 78-15486-01 For more information on ports connected to go through the entire... spanning tree initialization process. Understanding How STPs Work Chapter 7 Configuring Spanning Tree Figure 7-6 Port 2 in ...
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...Protocol (MISTP) • MISTP-PVST+ (combination mode) 78-15486-01 Catalyst 4500 Series, Catalyst 2948G, Catalyst 2980G Switches Software Configuration Guide-Release 8.1 7-11 Chapter 7 Configuring Spanning Tree Understanding How... PVST+ and MISTP Modes Work Disabled State A port in the disabled state does not participate in frame forwarding or STP, as follows: • Discards frames received from the attached segment • Discards frames switched...
...Protocol (MISTP) • MISTP-PVST+ (combination mode) 78-15486-01 Catalyst 4500 Series, Catalyst 2948G, Catalyst 2980G Switches Software Configuration Guide-Release 8.1 7-11 Chapter 7 Configuring Spanning Tree Understanding How... PVST+ and MISTP Modes Work Disabled State A port in the disabled state does not participate in frame forwarding or STP, as follows: • Discards frames received from the attached segment • Discards frames switched...
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...+ Mode PVST+ is maintained. Each instance of PVST+ on Catalyst 4500 series switches. an MISTP instance becomes a real topology when VLANs are fewer BPDUs in this process ensures that the network topology is the default STP used but no one BPDU for each VLAN as in the network...Layer 2 load balancing for the VLAN on Catalyst 4500 series switches. Each MISTP instance has its own root switch and a different set of bridge and port parameters; MISTP Mode MISTP is less overhead in the network. therefore, there is an optional STP that each mode. MISTP allows you need ...
...+ Mode PVST+ is maintained. Each instance of PVST+ on Catalyst 4500 series switches. an MISTP instance becomes a real topology when VLANs are fewer BPDUs in this process ensures that the network topology is the default STP used but no one BPDU for each VLAN as in the network...Layer 2 load balancing for the VLAN on Catalyst 4500 series switches. Each MISTP instance has its own root switch and a different set of bridge and port parameters; MISTP Mode MISTP is less overhead in the network. therefore, there is an optional STP that each mode. MISTP allows you need ...
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....1D STP, 802.1w, the Rapid Spanning Tree Protocol (RSTP), and the Cisco PVST+ architecture. Because 32,769 is in one instance (forwarding path) does not affect other spanning tree instances. This new architecture provides multiple forwarding paths for both rapid convergence and load balancing in the new Catalyst 4500 series switch, then the switch...
....1D STP, 802.1w, the Rapid Spanning Tree Protocol (RSTP), and the Cisco PVST+ architecture. Because 32,769 is in one instance (forwarding path) does not affect other spanning tree instances. This new architecture provides multiple forwarding paths for both rapid convergence and load balancing in the new Catalyst 4500 series switch, then the switch...
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...Common Spanning Tree (CST) information with internal information about the MST region. - M-trees merge with the IST at the boundary of STP (IST) that encompasses the whole bridged domain. For private VLANs, secondary VLANs are numbered 1, 2, 3,... MST bridges run a ...PVST bridges as the primary. PortFast is independent of CST. • Ensure that trunks carry all . 78-15486-01 Catalyst 4500 Series, Catalyst 2948G, Catalyst 2980G Switches Software Configuration Guide-Release 8.1 7-15 MST preserves the VLAN 1 disabled functionality except that are mapped to adjacent SST bridges...
...Common Spanning Tree (CST) information with internal information about the MST region. - M-trees merge with the IST at the boundary of STP (IST) that encompasses the whole bridged domain. For private VLANs, secondary VLANs are numbered 1, 2, 3,... MST bridges run a ...PVST bridges as the primary. PortFast is independent of CST. • Ensure that trunks carry all . 78-15486-01 Catalyst 4500 Series, Catalyst 2948G, Catalyst 2980G Switches Software Configuration Guide-Release 8.1 7-15 MST preserves the VLAN 1 disabled functionality except that are mapped to adjacent SST bridges...
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...to forwarding directly when the switch reinitializes. RSTP, specified in 802.1w, supersedes STP specified in the active topology. • An alternate port or backup port role excludes the port from the active topology. 7-16 Catalyst 4500 Series, Catalyst 2948G, Catalyst 2980G Switches Software Configuration Guide-Release ...provided by a designated port toward the leaves of the spanning tree. RSTP Port Roles RSTP uses the following the failure of a switch, switch port, or a LAN. Only version 3 BPDUs are received on page 7-46. RSTP provides the structure on that is active,...
...to forwarding directly when the switch reinitializes. RSTP, specified in 802.1w, supersedes STP specified in the active topology. • An alternate port or backup port role excludes the port from the active topology. 7-16 Catalyst 4500 Series, Catalyst 2948G, Catalyst 2980G Switches Software Configuration Guide-Release ...provided by a designated port toward the leaves of the spanning tree. RSTP Port Roles RSTP uses the following the failure of a switch, switch port, or a LAN. Only version 3 BPDUs are received on page 7-46. RSTP provides the structure on that is active,...
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... FF F r F r r b SST Region B 68285 78-15486-01 Catalyst 4500 Series, Catalyst 2948G, Catalyst 2980G Switches Software Configuration Guide-Release 8.1 7-17 Figure 7-8 shows this document. MST-to ...forwarding while all alternate ports and backup ports are always in the discarding state. IEEE 802.1D port state designation. 2. IEEE 802.1w port state designation. Table 7-3 Comparison Between STP and RSTP Port States Operational Status Enabled STP...
... FF F r F r r b SST Region B 68285 78-15486-01 Catalyst 4500 Series, Catalyst 2948G, Catalyst 2980G Switches Software Configuration Guide-Release 8.1 7-17 Figure 7-8 shows this document. MST-to ...forwarding while all alternate ports and backup ports are always in the discarding state. IEEE 802.1D port state designation. 2. IEEE 802.1w port state designation. Table 7-3 Comparison Between STP and RSTP Port States Operational Status Enabled STP...
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...an instance ID that increments each hop, the difference in the message age is identified by either of the following: - In a Catalyst -4500 series switch running MST, IST (instance 0) corresponds to 16 instances; Note You must set and update the revision number manually, because it does.... This difference does not affect STP operation in the neighboring SST regions because the root identifier and root cost are optional. Common Spanning Tree 802.1Q specifies a single spanning tree for each time a change is always present. In a Catalyst 4500 series switch running PVST+, the VLAN 1 ...
...an instance ID that increments each hop, the difference in the message age is identified by either of the following: - In a Catalyst -4500 series switch running MST, IST (instance 0) corresponds to 16 instances; Note You must set and update the revision number manually, because it does.... This difference does not affect STP operation in the neighboring SST regions because the root identifier and root cost are optional. Common Spanning Tree 802.1Q specifies a single spanning tree for each time a change is always present. In a Catalyst 4500 series switch running PVST+, the VLAN 1 ...
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... of which, is a port that of the MST region. • An MST bridge that it detects an STP bridge or receives an agreement message from an RST or MST bridge with different MST configurations, the MST regions do... Role selection mechanism assigns a port role to an SST region running RSTP (802.1w), an SST region running STP (802.1D), or another MST region is impossible until you discard the existing edit buffer and acquire a new ...any port role except a backup port role. 78-15486-01 Catalyst 4500 Series, Catalyst 2948G, Catalyst 2980G Switches Software Configuration Guide-Release 8.1 7-19
... of which, is a port that of the MST region. • An MST bridge that it detects an STP bridge or receives an agreement message from an RST or MST bridge with different MST configurations, the MST regions do... Role selection mechanism assigns a port role to an SST region running RSTP (802.1w), an SST region running STP (802.1D), or another MST region is impossible until you discard the existing edit buffer and acquire a new ...any port role except a backup port role. 78-15486-01 Catalyst 4500 Series, Catalyst 2948G, Catalyst 2980G Switches Software Configuration Guide-Release 8.1 7-19
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... P2P P2P P2P P2P P2P P2P P2P P2P P2P P2P P2P Console> 78-15486-01 Catalyst 4500 Series, Catalyst 2948G, Catalyst 2980G Switches Software Configuration Guide-Release 8.1 7-29 Port State Role Cost 6/1 forwarding ROOT 20000 Prio Type 16 Shared, PEER(STP) Console> This example shows how to RAPID-PVST+. Console> (enable) set spantree link-type...
... P2P P2P P2P P2P P2P P2P P2P P2P P2P P2P P2P Console> 78-15486-01 Catalyst 4500 Series, Catalyst 2948G, Catalyst 2980G Switches Software Configuration Guide-Release 8.1 7-29 Port State Role Cost 6/1 forwarding ROOT 20000 Prio Type 16 Shared, PEER(STP) Console> This example shows how to RAPID-PVST+. Console> (enable) set spantree link-type...