SRWE Section 2 STP Etherchannel (mod5-6) Study Guide

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NAME:____________________________ DATE: __________ Northampton Community College CISC267 – SRWE Section 2 (Modules 5-6) Study Guide 1. Define Spanning Tree Protocol. Spanning Tree Protocol (STP) is a Layer 2 network protocol used to prevent looping within a network topology. STP was created to avoid the problems that arise when computers exchange data on a local area network (LAN) that contains redundant paths. 2. What design features are required to use spanning tree protocol? Redundant links between Layer 2 switches and removing single points of failure with multiple Layer 2 switches 3. Why is it recommended to leave STP turned “on” on your switches? It is recommended to leave STP turned "on" on switches for several reasons: Loop prevention: STP helps to prevent network loops by disabling redundant links in the network, which would otherwise cause broadcast storms and severely affect network performance. Redundancy management: STP provides a mechanism for managing network redundancy, enabling the switches to automatically reconfigure the network topology in case of a failure. Improved network stability: With STP enabled, switches can detect and resolve network issues more quickly, leading to a more stable network. Efficient use of network resources: STP helps to optimize the use of network bandwidth by disabling redundant links and only forwarding traffic over the best path. Overall, leaving STP enabled on switches helps to ensure a stable, efficient, and reliable network. It is considered a best practice in network design to have STP enabled on switches in order to prevent network issues and improve network performance. 4. What is a BPDU? Bridge Protocol Data Units (BPDUs) are the messages that are transmitted across LAN networks to enable switches to participate in Spanning Tree Protocol (STP) by gathering information about each other. It contains information regarding switch ports such as port ID, port priority, port cost, and MAC addresses. 5. What is a bridge ID? How is it used in STP? A bridge ID is a unique identifier used in the Spanning Tree Protocol (STP) to identify a specific bridge in a network. It consists of two parts: a priority value and the MAC address of the bridge. The priority value is used to determine the root bridge in the network and the MAC address ensures uniqueness. In STP, the bridge with the lowest bridge ID is elected as the root bridge, and all other bridges calculate the best path to the root bridge. The bridge ID is used to break ties when multiple bridges have the same priority value. The use of a unique bridge ID in STP helps to ensure a loop-free topology in the network, by disabling links that would otherwise cause network loops. 6. What is included in the 12-bit extended system ID? The 12-bit extended system ID is part of the bridge ID used in the Spanning Tree Protocol (STP). The bridge ID is a unique identifier for each bridge in the network and is used to determine the root bridge. The 12-bit extended system ID is used to provide additional information about the VLANs that a switch is participating in. This information is combined

with the priority value in the bridge ID to determine the root bridge for each VLAN in the network. The 12-bit extended system ID is used in the Rapid Spanning Tree Protocol (RSTP), which is an enhancement of the original STP. RSTP provides faster convergence and improved network stability compared to STP and is commonly used in modern networks. In summary, the 12-bit extended system ID is used to provide additional information about the VLANs a switch is participating in and is used in the Rapid Spanning Tree Protocol to improve network stability and efficiency. 7. What is a root switch? How does a switch become the root? In the Spanning Tree Protocol (STP), the root switch is the switch that is designated as the central reference point for all other switches in the network. All other switches calculate the best path to the root switch and use this information to determine the network's loop-free topology. A switch becomes the root switch by being elected as such by the other switches in the network. The election process is based on the bridge ID of each switch, which is a unique identifier consisting of a priority value and the MAC address of the switch. The switch with the lowest bridge ID is elected as the root switch. If multiple switches have the same priority value, the switch with the lowest MAC address is elected as the root switch. The election process occurs when the network is initialized, and the root switch is periodically re-elected to ensure that the network remains stable. In summary, a root switch is the designated central reference point in the network, and a switch becomes the root switch by being elected based on its unique bridge ID. 8. Explain the following varieties of STP. Identify differences between them: a. STP - Spanning Tree Protocol (STP) - STP is a network protocol that is used to prevent loops in a network by disabling redundant links. STP operates by electing a root switch and determining the best path to the root for all other switches in the network. STP uses a bridge ID to identify each switch, and the switch with the lowest bridge ID is elected as the root switch. STP is a basic protocol and has a slow convergence time, making it less efficient for modern networks. b. RSTP - Rapid Spanning Tree Protocol (RSTP) - RSTP is an improvement over the original STP and provides faster convergence times. RSTP uses a more efficient election process and supports faster transition to forwarding state, leading to a more stable network. RSTP also includes support for edge ports, which are ports that are not connected to other switches and can transition directly to a forwarding state. c. Rapid PVST+ - Rapid PVST+ - Rapid PVST+ is a proprietary version of RSTP that is used by Cisco systems. Rapid PVST+ provides rapid convergence times and supports per-VLAN spanning tree (PVST), allowing for multiple spanning trees in a single network. d. MSTP - Multiple Spanning Tree Protocol (MSTP) - MSTP is an extension of RSTP that provides support for multiple spanning trees in a single network. MSTP allows for the creation of multiple instances of STP, each with its own root switch and topology, leading to improved network scalability. e. PVST+ - Per-VLAN Spanning Tree Plus (PVST+) - PVST+ is a proprietary version of STP that is used by Cisco systems. PVST+ provides support for multiple spanning trees, one for each VLAN in the network. This allows for improved network scalability and more efficient use of network resources.

In summary, the differences between these STP varieties are primarily related to the speed of convergence, support for multiple spanning trees, and vendor-specific features. RSTP and Rapid PVST+ provide faster convergence times compared to STP, while MSTP and PVST+ provide support for multiple spanning trees. 9. Based on the above graphic, identify the following: a. Root Bridge - Root Bridge - The Root Bridge is the switch with the lowest bridge ID in the network and is used as a reference point for all other switches. In the graphic, the Root Bridge is labeled as "Switch 1". b. Root Ports - Root Ports - Root Ports are the ports on non-root switches that provide the best path to the Root Bridge. In the graphic, the Root Ports are labeled as "RP". c. Designated Ports - Designated Ports - Designated Ports are the ports on each switch that provide the best path to the root for a particular segment. In the graphic, the Designated Ports are labeled as "DP". d. Blocked/Alt ports - Blocked/Alt Ports - Blocked/Alt Ports are ports that are not forwarding traffic in order to prevent network loops. In the graphic, the Blocked/Alt Ports are labeled as "BP". These ports remain in a blocked state until a failure is detected on the network, at which point they can transition to a forwarding state. 10. What are the STP states? The Spanning Tree Protocol (STP) has five states: Blocking - In this state, the port does not participate in forwarding traffic and is effectively disabled. This state is used to prevent network loops. Listening - In this state, the port prepares to participate in forwarding traffic. This state is used to ensure that the network has stabilized and that there are no loops. Learning - In this state, the port learns the MAC addresses of devices connected to the network. This information is used to build the forwarding database. Forwarding - In this state, the port participates in forwarding traffic and can send and receive data. Disabled - In this state, the port is physically disabled and does not participate in forwarding traffic. This state is typically used for maintenance or troubleshooting purposes. In summary, the STP states represent the different stages in which a port transitions from a blocked state to a forwarding state and are used to prevent network loops and ensure a stable network topology. 11. What are the RSTP states? Rapid Spanning Tree Protocol (RSTP) has three main states:

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Discarding - In this state, the port does not participate in forwarding traffic and is effectively disabled. This state is used to prevent network loops. Learning - In this state, the port prepares to participate in forwarding traffic by learning the MAC addresses of devices connected to the network. This information is used to build the forwarding database. Forwarding - In this state, the port participates in forwarding traffic and can send and receive data. In comparison to STP, RSTP has fewer states and faster convergence times, making it more efficient for modern networks. The main difference between STP and RSTP is that RSTP uses a more efficient election process and supports faster transition to the forwarding state. 12. What are the port roles defined by RSTP? RSTP (Rapid Spanning Tree Protocol) defines the following port roles in a network: Root Port: The port on a non-root switch that provides the fastest path to the root bridge. Designated Port: The port on a network segment that is responsible for forwarding traffic to and from the segment. Alternate Port: A backup port that provides an alternative path to the root bridge in case of failure of the designated port. Backup Port: A port that provides backup connectivity to the root bridge in case of failure of the root port or designated port. Disabled Port: A port that is not participating in the spanning tree and is not forwarding traffic. 13. What command displays the status of STP for all VLANs? The command to display the status of STP (Spanning Tree Protocol) for all VLANs on a Cisco device is: show spanning-tree vlan [vlan- id ] Where vlan-id is an optional parameter that specifies the VLAN number for which you want to display STP information. If the vlan-id is not specified, STP information for all VLANs will be displayed. 14. What technology allows one to increase the bandwidth of an uplink between and access layer switch and a distribution layer switch? One technology that can increase the bandwidth of an uplink between an access layer switch and a distribution layer switch is Link Aggregation (LAG) or EtherChannel. It allows multiple physical links to be combined into a single logical link, providing higher bandwidth and redundancy. 15. Explain the two main protocols used for link aggregation? The two main protocols used for link aggregation are Link Aggregation Control Protocol (LACP) and Static Link Aggregation. LACP: LACP is a dynamic protocol that is part of the IEEE 802.3ad standard. It allows the switch and the endpoint device to negotiate and automatically bundle multiple physical links into a single logical link. LACP continuously monitors the physical links to ensure they are functioning properly, and if a link fails, it will automatically reroute traffic over the remaining links. Static Link Aggregation: As the name suggests, Static Link Aggregation involves manually configuring the bundle of physical links into a single logical link. This method does not provide

any automatic monitoring or failover capabilities but is simple to configure and is often used in smaller networks where the risk of link failure is low. 16. What settings need to be identical for a port channel to be successfully implemented? For a port channel to be successfully implemented, the following settings need to be identical: Mode: Both ports must be configured to operate in the same mode, either access or trunk mode, to ensure they are both sending and receiving the same type of traffic. VLANs: Both ports must be configured with the same VLANs to ensure they are passing the same set of VLAN tagged frames. Speed and Duplex: Both ports must be configured with the same speed and duplex setting to ensure they are operating at the same speed and using the same duplex method. Link Aggregation Protocol: Both ports must be configured to use the same Link Aggregation Protocol, either LACP or static link aggregation, to ensure they are bundling the links in the same way. Port Channel number: Both ports must be assigned to the same port channel number to ensure they are part of the same logical link. Ensuring that these settings are identical on both ports is critical for successful implementation of a port channel. 17. Identify the configuration modes for PAgP, LACP. PAgP (Port Aggregation Protocol) and LACP (Link Aggregation Control Protocol) are both Link Aggregation protocols used to bundle multiple physical links into a single logical link. The configuration modes for these two protocols are as follows: PAgP Configuration Modes: Auto: The port will accept aggregation with any PAgP-enabled port. Desirable: The port will initiate aggregation with PAgP-enabled ports that are configured as "Auto" or "Desirable". Passive: The port will not initiate aggregation but will accept aggregation if initiated by another PAgP-enabled port that is configured as "Desirable". LACP Configuration Modes: Active: The port will actively initiate negotiations with other LACP-enabled ports to form a link aggregation. Passive: The port will not actively initiate negotiations but will respond to negotiations initiated by other LACP-enabled ports. 18. Explain the problem in the output above.

The output signifies that Port channel 1 is currently down on layer 2 and that Fa0/1-3 are all singular ports that aren’t bundled into a port channel. Also, the flags signify the state of each port.

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SRWE Section 2 STP Etherchannel (mod5-6) Study Guide

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