Free CCNA | Rapid Spanning Tree Protocol | Day 22 | CCNA 200-301 Complete Course

Welcome to Jeremy’s IT Lab

In this video, Jeremy introduces the topic of spanning tree and focuses on rapid spanning tree, specifically Cisco's version called rapid per-VLAN spanning tree. He explains the importance of understanding classic spanning tree before diving into rapid spanning tree.

Comparing Different Versions of STP

• Classic Spanning Tree Protocol (IEEE 802.1D) is the original protocol but can be slow and does not support load balancing.

• Per-VLAN Spanning Tree Plus (PVST+) is Cisco's upgrade to 802.1D, allowing each VLAN to have its own STP instance for load balancing.

• Rapid Spanning Tree Protocol (RSTP or IEEE 802.1w) improves convergence time but still runs only one STP instance shared by all VLANs.

• Rapid Per-VLAN Spanning Tree Plus (Rapid PVST+) is Cisco's upgrade to RSTP, featuring improved speed and separate STP instances for each VLAN.

• Multiple Spanning Tree Protocol (MSTP or IEEE 802.1s) allows grouping multiple VLANs into different instances for better load balancing.

Summarizing Different Versions of Spanning Tree

Jeremy summarizes the different versions of spanning tree protocols, including industry standards and Cisco proprietary versions.

Classic Spanning Tree Protocol (IEEE 802.1D)

• The original spanning tree protocol published in 1990.

• All VLANs share one STP instance, limiting load balancing capabilities.

Per-VLAN Spanning Tree Plus (PVST+)

• Cisco's upgrade to 802.1D with separate STP instances for each VLAN.

• Allows load balancing by blocking different ports in each VLAN.

Rapid Spanning Tree Protocol (IEEE 802.1w)

• Faster convergence and adaptation to network changes compared to 802.1D.

• Runs only one STP instance shared by all VLANs, limiting load balancing.

Rapid Per-VLAN Spanning Tree Plus (Rapid PVST+)

• Cisco's upgrade to 802.1w with separate STP instances for each VLAN.

• Offers improved speed and load balancing capabilities.

Multiple Spanning Tree Protocol (IEEE 802.1s)

• Uses modified RSTP mechanics and allows grouping multiple VLANs into different instances.

• Provides load balancing capabilities and is superior to Cisco's rapid-PVST.

Conclusion

Jeremy concludes the video by highlighting the benefits of MSTP for networks with many VLANs and mentioning that Cisco devices run industry-standard MSTP without their own version.

Timestamps are approximate and may not be exact.

Understanding Rapid Spanning Tree Protocol (RSTP)

In this section, the instructor introduces RSTP and explains how it differs from the standard 802.1D STP. The benefits of learning RSTP after understanding classic STP and PVST+ are highlighted.

Introduction to RSTP

• RSTP is not a timer-based spanning tree algorithm like 802.1D.

• It offers an improvement over the 30 seconds or more that 802.1D takes to move a link to forwarding.

• The protocol uses a bridge-bridge handshake mechanism for faster port transition to forwarding state.

Similarities between STP and RSTP

• Both serve the purpose of blocking specific ports to prevent Layer 2 loops.

• Root bridge election follows the same rules as in STP, with the switch having the lowest bridge ID becoming the root bridge.

• Root port election also follows similar rules based on root cost, neighbor bridge ID, and neighbor port ID.

• Designated ports are elected using the same rules as in STP.

Differences between STP and RSTP

• Port costs were updated for rapid spanning tree to accommodate faster speeds.

• Classic spanning tree defines port speeds up to 10 Gbps, while RSTP's cost values were expanded for higher speeds.

• Port states in rapid spanning tree are simplified into three states: discarding (combining blocking and disabled), learning, and forwarding.

• Port roles remain unchanged for root ports and designated ports but introduce two new roles: alternate port role and backup port role.

Understanding Port Costs and States in RSTP

This section focuses on port costs in rapid spanning tree protocol (RSTP) compared to classic spanning tree. It also explains the simplified port states in RSTP.

Port Costs in RSTP

• Classic spanning tree assigns a cost of 1 to port speeds faster than 10 Gbps.

• RSTP expands the cost values for faster speeds, such as 10 mbps (2 million), 100 mbps (2 hundred thousand), and so on.

• A 10 terabit-per-second interface would have a cost of 2.

Simplified Port States in RSTP

• Rapid spanning tree simplifies the port states into three: discarding (combining blocking and disabled), learning, and forwarding.

• The listening state is no longer used in RSTP.

• Administratively disabled ports are in the discarding state, while ports blocking traffic to prevent loops are also in the discarding state.

Understanding Port Roles in RSTP

This section explains the different port roles in rapid spanning tree protocol (RSTP) and how they compare to classic spanning tree.

Root Port Role

• The root port role remains unchanged in RSTP.

• The port with the lowest root cost becomes the root port for a switch.

• The root bridge does not have a root port.

Designated Port Role

• The designated port role remains unchanged in RSTP.

• The segment's designated port is determined by sending the best BPDU on that segment, with only one designated port per segment.

Non-designated Port Roles

• In classic spanning tree, non-designated ports exist as a single role.

• In RSTP, non-designated ports are divided into two separate roles: alternate port role and backup port role.

Alternate Port and UplinkFast

This section discusses the concept of alternate ports in spanning tree protocol (STP) and how they function as backups to root ports. It also introduces the optional feature called UplinkFast, which is built into Rapid Spanning Tree Protocol (RSTP).

Alternate Port

• An alternate port serves as a backup to the root port.

• If the root port fails, the switch can immediately move its best alternate port to forwarding, becoming the new root port.

• This immediate transition to forwarding state is similar to the functionality of UplinkFast in classic STP.

UplinkFast

• UplinkFast is an optional feature in classic STP that has been incorporated into RSTP.

• It allows for rapid transitioning of blocking or discarding ports to forwarding without delay.

• No additional configuration is required when using RSTP or Rapid PVST+.

BackboneFast

This section explains another optional feature incorporated into RSTP called BackboneFast. It describes how it helps with rapid convergence when a switch's root port fails.

• BackboneFast is another STP optional feature built into RSTP.

• When a switch's root port fails, it assumes itself as the root bridge and starts sending its own BPDUs (Bridge Protocol Data Units) to other switches.

• Without BackboneFast, receiving switches would ignore these BPDUs until their non-designated ports transition to forwarding state and forward superior BPDUs back.

• BackboneFast allows for expiring the max age timer on interfaces and rapidly forwarding superior BPDUs from one switch to another.

Summary of UplinkFast and BackboneFast

This section provides a summary of UplinkFast and BackboneFast features in classic STP and their incorporation into RSTP.

• UplinkFast and BackboneFast are optional features in classic STP.

• They need to be configured on the switch when using classic STP, but they are built-in features of RSTP.

• If a switch is running RSTP, there is no need to configure UplinkFast and BackboneFast separately.

• It is not necessary to have a detailed understanding of these features for the CCNA exam. Knowing their names and basic purpose is sufficient.

Importance of Effective Google Search Skills

This section emphasizes the importance of developing effective Google search skills for network engineers and suggests using Google to find more information on specific topics.

• Learning how to effectively search on Google for information is essential for network engineers.

• Google searches can provide valuable resources for further learning about specific topics covered in videos or during daily work as a network engineer.

• While it's not necessary to have an in-depth understanding of UplinkFast and BackboneFast for the CCNA exam, utilizing good search skills can help expand knowledge beyond the basics.

Backup Port Role in RSTP

This section introduces the backup port role in Rapid Spanning Tree Protocol (RSTP) and explains its function as a backup for designated ports.

Backup Port Role

• The backup port role in RSTP applies to discarding ports that receive superior BPDUs from another interface on the same switch.

• This situation occurs when two interfaces are connected to the same collision domain via a hub (although hubs are not commonly used in modern networks).

• When SW2's designated port fails, its backup port immediately starts forwarding traffic as a designated port.

Determining Designated Port with Lowest Port ID

This section explains how the switch determines which port will be the designated port and which will be the backup port based on their port IDs.

• The interface with the lowest port ID is selected as the designated port, while the other interface becomes the backup port.

• In the provided network topology, SW4 chooses G0/1 as its root port over G0/0 because G0/1 has a lower neighbor bridge ID (SW2 has a lower MAC address).

Quiz Question: Identifying Root Bridge and Port Roles

This section presents a quiz question to identify the root bridge and RSTP port roles for each switch interface in the network.

• The root bridge in this network is SW1, elected due to its lowest MAC address.

• SW1's interfaces are designated ports, serving as root ports for each switch.

• SW2 and SW3 have obvious root ports with the lowest root cost.

• SW4's root port is G0/1 because it receives superior BPDUs from SW2 with a lower neighbor bridge ID.

Timestamps were used to associate bullet points with specific parts of the transcript.

New Section

This section discusses the STP modes and the roles of SW3's G0/1 and SW4's G0/0 interfaces.

STP Modes and Interface Roles

• SW3's G0/1 is a backup port as it receives the superior BPDU with a lower port ID from the same switch.

• SW4's G0/0 is an alternate port as it receives the superior BPDU from a different switch.

New Section

This section provides an overview of the CLI commands used to configure STP modes on Cisco switches.

CLI Configuration for STP Modes

• There are three STP modes available on Cisco switches: MST, PVST, and rapid-PVST.

• Rapid-PVST is the default mode on modern Cisco switches.

• The command "SPANNING-TREE MODE RAPID-PVST" can be used to ensure rapid-PVST mode is enabled.

• The command "SHOW SPANNING-TREE" can be used to confirm the spanning tree protocol in use.

New Section

This section explains how to verify and interpret the output of the "SHOW SPANNING-TREE" command.

Verifying Spanning Tree Protocol

• The output of "SHOW SPANNING-TREE" confirms that rapid PVST+ (Rapid STP) is running.

• The status of SW3's G0/1 interface is listed as BLK (blocking), which corresponds to discarding state in rapid STP.

• The output of "SHOW SPANNING-TREE" on SW4 shows that its G0/0 interface is an alternate port.

New Section

This section discusses the compatibility of rapid STP with classic STP and the operation of interfaces between switches running different STP versions.

Compatibility of Rapid STP with Classic STP

• Rapid STP is compatible with classic STP.

• Interfaces on a rapid STP-enabled switch connected to a classic STP-enabled switch will operate in classic STP mode.

• The operation, timers, and state process remain the same for these interfaces.

• In our network diagram, if SW4 was running classic STP, SW2 and SW3 would make their interfaces run in classic STP mode while their interfaces connected to SW1 would remain in rapid STP mode.

New Section

This section explains the differences between the BPDU for RSTP (Rapid Spanning Tree Protocol) and classic spanning tree.

Differences in RSTP BPDU

• The RSTP BPDU has a protocol version of 2, while the classic spanning tree has a version of 0.

• The RSTP BPDU uses all 8 bits for BPDU flags, whereas the classic spanning tree only uses two bits (1st bit and 8th bit).

• These flags are used in the negotiation process that allows rapid STP to converge faster than classic STP.

New Section

This section discusses additional differences between RSTP and classic spanning tree, including BPDUs originator, aging process, and topology changes handling.

Additional Differences in RSTP

• In rapid STP, all switches originate and send their own BPDUs from their designated ports. In contrast, only the root bridge originated BPDUs in classic spanning tree.

• Switches running rapid STP send their own BPDUs and age BPDU information more quickly compared to classic STP.

• In rapid STP, a switch considers a neighbor lost if it misses 3 BPDUs (6 seconds) and flushes all MAC addresses learned on that interface.

• Topology changes in rapid STP are handled by clearing MAC table entries and adjusting the path for traffic.

New Section

This section provides an overview of the differences between RSTP and classic spanning tree BPDUs.

Comparison of RSTP and Classic STP BPDUs

• The RSTP BPDU has a protocol version of 2, while the classic spanning tree has a version of 0.

• The RSTP BPDU uses all 8 bits for BPDU flags, allowing faster convergence.

• Understanding the details of the BPDU is not required for CCNA certification.

New Section

This section explains one major difference between RSTP and classic spanning tree regarding BPDUs originator.

Originator of BPDUs

• In classic spanning tree, only the root bridge originated BPDUs, while in rapid STP, all switches originate and send their own BPDUs from their designated ports.

New Section

This section discusses additional differences between RSTP and classic spanning tree, including sending own BPDUs, aging process, and flushing MAC addresses.

Additional Differences in RSTP

• All switches running rapid STP send their own BPDUs.

• Rapid STP switches age BPDU information more quickly compared to classic STP.

• A switch considers a neighbor lost if it misses 3 BPDUs (6 seconds) in rapid STP. It then flushes all MAC addresses learned on that interface.

New Section

This section provides a brief overview of how topology changes are handled in rapid STP.

Handling Topology Changes in Rapid STP

• When a connection is cut off, the switch clears all entries for that interface from its MAC table.

• The switch then designates the other interface as the root port.

• Traffic will follow a new path after relearning the MAC address on the new interface.

New Section

This section introduces RSTP link types and explains the concept of an edge port.

RSTP Link Types

• RSTP distinguishes between three link types: edge, point-to-point, and shared.

• An edge port is connected to an end host and moves directly to forwarding without negotiation.

• Portfast functionality is built into RSTP, making edge ports similar to portfast-enabled ports.

New Section

This section discusses different types of link types in spanning tree protocol and their configurations.

Edge Ports

• Edge ports are connected to end hosts.

• They can move straight to the forwarding state without the negotiation process.

• Configured by enabling portfast on the port.

• Command: spanning-tree portfast

Point-to-Point Ports

• These ports connect directly to another switch.

• Function in full-duplex mode.

• No need for explicit configuration, as the switch can detect the connection type automatically.

Shared Ports

• Shared ports connect to a hub.

• Must function in half duplex due to the likelihood of collisions.

• No need for explicit configuration, as the switch can detect the connection type automatically.

New Section

This section further explains point-to-point and shared link types and provides examples from a network diagram.

Edge Ports Configuration Example

• All ports connected to PCs should be configured as edge ports.

Point-to-Point Link Type

• These links connect switches directly.

• Full-duplex mode is used.

Shared Link Type

• These links connect to a hub.

• Half-duplex mode is used.

New Section

This section summarizes different versions of spanning tree protocols and focuses on Rapid Spanning Tree Protocol (RSTP).

Comparison of STP Versions

1. Classic STP (802.1D)

2. PVST+ (Cisco's upgrade with separate instances for each VLAN)

3. Rapid STP (802.1w)

4. Rapid PVST+ (Cisco's version with separate instances for each VLAN)

5. Multiple Spanning Tree Protocol (MSTP) - industry standard

RSTP Features

• RSTP is an evolution of classic STP.

• Uses a negotiation process instead of timers for rapid state transitions.

• Port states in RSTP: Discarding, Learning, and Forwarding.

New Section

This section explains the different port roles and link types in RSTP.

RSTP Port Roles

• Root and designated ports are the same as in classic STP.

• Alternate ports are discarding ports that receive a superior BPDU from another switch.

• Backup ports receive a superior BPDU from an interface on the same switch (rarely used).

Optional Features of Classic STP Built into RSTP

• UplinkFast, BackboneFast, and PortFast are built-in features of RSTP.

• UplinkFast provides fast convergence for uplink failures.

• BackboneFast speeds up convergence when the root bridge fails.

New Section

This section concludes the discussion on RSTP by explaining edge ports and summarizing link types.

Edge Ports

• Connected to end hosts (e.g., PCs).

• Configured by enabling portfast on the interface.

Link Types in RSTP

1. Edge Ports: Connected to end hosts, configured with portfast.

2. Point-to-point Ports: Directly connected to another switch, full-duplex mode.

3. Shared Ports: Connected to a hub, must use half-duplex mode.

Hubs are no longer commonly used in modern networks.

New Section

This section briefly mentions Boson Software's ExSim practice exams for CCNA preparation.

New Section

In this section, the video discusses quiz questions related to IEEE 802.1D and IEEE 802.1w standards, as well as configuring edge ports in RSTP.

Quiz Question 2 - IEEE 802.1D Optional Features in IEEE 802.1w Standard

• The question asks about the optional features built into the IEEE 802.1w standard that allow ports to move rapidly to the forwarding state.

• The correct answers are B, portfast; D, uplinkfast; and E, backbonefast.

• A, root guard; C, BPDU guard; and F, loop guard are spanning tree optional features but not built-in features of RSTP.

Configuring an RSTP Edge Port

• To configure an 802.1w edge port for immediate traffic forwarding from connected hosts, use the command spanning-tree portfast.

Identifying Root Bridge and Port Roles in a Network

• The root bridge in the network is SW1 with the lowest priority.

• The designated ports are determined based on factors such as bridge ID and root cost.

• SW4 selects its G0/0 interface as its root port because SW3 has a lower bridge ID than SW2.

• SW2's interface is selected as designated due to its lower root cost.

Link Types in RSTP Network

• Ports connected to end hosts should be configured as edge ports.

• Full-duplex connections between switches are point-to-point links.

• Half-duplex connections with a hub are shared links.

Boson ExSim Practice Question - Optional STP Features

• The question asks about the optional STP feature that reduces convergence time by immediately placing edge ports into a forwarding state.

• The correct answer is C, PortFast.

Boson ExSim Practice Exam Explanation

• Boson ExSim provides detailed explanations for practice exam questions, including summaries of other optional STP features such as loop guard, root guard, BPDU guard, and BPDU filter.

Conclusion and Recommendation

• Boson ExSim is recommended as a study resource for CCNA exams.

• Supplementary materials and flashcard decks are available for further study.

Timestamps are approximate and may vary slightly.

New Section

This section acknowledges and thanks the individuals who have supported the channel.

List of Supporters

• Yousif, Kone, Boson Software, the creators of ExSim, Sidi, Magrathea, Devin, Charlsetta, Lito, Yonatan, Mike, Aleksander, Vance, and Gerrard are thanked for their support.

New Section

The speaker addresses the JCNP-level members and encourages viewers to subscribe to the channel.

JCNP-Level Members

• The speaker mentions that this is a list of JCNP-level members as of May 27th 2020.

• Viewers who signed up recently and do not see their names on the list are assured that they will be included in future videos.

Call to Action

• Viewers are encouraged to subscribe to the channel, like the video, leave a comment, and share it.