VLAN Trunking and Tagging

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Questions and Answers

What is the primary function of Spanning Tree Protocol (STP) in a network?

To manage VLAN configurations on multiple switches

To optimize network performance by directing traffic through the shortest path

To provide a redundant path for data transmission between switches

To prevent Layer 2 loops by blocking redundant paths (correct)

What is the purpose of the broadcast frame mentioned in the context of Layer 2 loops?

To establish a connection between two devices on the same VLAN

To inform switches of network topology changes

To create a loop by replicating itself across redundant paths (correct)

To test the availability of all network devices on the VLAN

Why are commercial switches equipped with Spanning Tree Protocol by default?

To prevent Layer 2 loops and ensure network stability (correct)

To facilitate faster data transfer between switches

To enhance security by restricting access to specific VLANs

To ensure compatibility with legacy network devices

What happens when a switch receives a broadcast frame while running Spanning Tree Protocol?

It blocks the broadcast frame if the port is in a blocking state Signup and view all the answers

In the example scenario of two switches with two connections, what would happen if Spanning Tree Protocol were not running?

Broadcast frames would be endlessly duplicated, causing a broadcast storm Signup and view all the answers

Which of the following statements about Spanning Tree Protocol is TRUE?

It is a Layer 2 protocol that prevents network loops by blocking redundant paths Signup and view all the answers

Which of these is NOT a benefit of using Spanning Tree Protocol?

Simplified network management by eliminating the need for manual configuration Signup and view all the answers

What is the main reason why Spanning Tree Protocol is essential for network stability?

It prevents broadcast storms caused by endless frame replication Signup and view all the answers

In a Spanning Tree environment, which device is responsible for identifying the best port to use for forwarding towards the root?

Losing switch Signup and view all the answers

What are the two elements that make up the bridge ID?

Priority and Base MAC address Signup and view all the answers

When multiple paths to the root bridge have identical costs, what is the next factor used to determine the best port?

The upstream switch bridge ID Signup and view all the answers

What is the purpose of Spanning Tree Protocol (STP)?

To prevent layer 2 loops Signup and view all the answers

What is the role of a designated port in a Spanning Tree environment?

To forward traffic to the root bridge Signup and view all the answers

How is the cost of a port determined in Spanning Tree?

Based on the bandwidth of the interface Signup and view all the answers

If a switch has two paths to the root bridge with different costs, what path will it choose?

The path with the lower cost Signup and view all the answers

What is the significance of a switch advertising its cost to itself as 0?

It indicates the switch is directly connected to the root bridge Signup and view all the answers

What is the role of BPDUs in Spanning Tree Protocol?

To establish the root bridge Signup and view all the answers

Which of the following statements is NOT true about Spanning Tree Protocol?

It is responsible for routing traffic between networks Signup and view all the answers

What is the primary purpose of Spanning Tree Protocol?

To prevent loops in a network by blocking redundant paths. Signup and view all the answers

Which of the following statements accurately describes the role of the root bridge in Spanning Tree Protocol?

The root bridge is the switch with the lowest bridge ID and determines which paths are allowed for traffic flow. Signup and view all the answers

What is the role of a designated port in Spanning Tree Protocol?

A designated port is a port that is responsible for forwarding traffic to other switches in the network. Signup and view all the answers

Which of the following statements correctly describes the process by which Spanning Tree Protocol determines the root bridge?

The root bridge is the switch with the lowest bridge ID, determined by its MAC address and priority. Signup and view all the answers

What is the significance of the Bridge Protocol Data Units (BPDUs) in Spanning Tree Protocol?

BPDUs are used to communicate information about the Spanning Tree topology, including bridge IDs and port states. Signup and view all the answers

How does Spanning Tree Protocol handle traffic forwarding on ports that are not designated ports?

Non-designated ports are in a blocking state, preventing traffic forwarding, to avoid creating loops in the network. Signup and view all the answers

What is the term for a port that is forwarding traffic away from the root bridge in Spanning Tree Protocol?

Designated port Signup and view all the answers

Why is Spanning Tree Protocol considered an essential component of a network infrastructure?

It prevents network loops and broadcast storms, ensuring reliable and efficient data transmission. Signup and view all the answers

How does Spanning Tree Protocol handle the scenario where two switches have the same bridge ID?

The switches negotiate a new bridge ID based on their MAC addresses and priority values. Signup and view all the answers

What is the impact of Spanning Tree Protocol on the latency of data packets?

Spanning Tree Protocol can slightly increase latency due to the time it takes for switches to learn the network topology. Signup and view all the answers

What would happen if a layer 2 switch sees Bridge Protocol Data Units on multiple ports?

It would disable and put one of the ports into a blocking state Signup and view all the answers

What is the role of the non-root bridge in Spanning Tree protocol?

It elects one root port on that device and blocks parallel paths Signup and view all the answers

What is the purpose of root guard in Spanning Tree protocol?

To train the switch to not change its root port Signup and view all the answers

What happens when a hacker sends crafted BPDUs to a switch?

The switch thinks the hacker has a lower bridge ID Signup and view all the answers

What is the purpose of BPDU guard in Spanning Tree protocol?

To aggressively shut down the functionality of a port if it sees BPDUs Signup and view all the answers

What is the limitation of Spanning Tree protocol in terms of network bandwidth?

It shuts down one of the links to prevent loops Signup and view all the answers

What is the purpose of link aggregation in networking?

To use all available bandwidth and prevent loops Signup and view all the answers

What is the role of the root bridge in Spanning Tree protocol?

All its ports for that VLAN will be forwarding Signup and view all the answers

What is the purpose of BPDU filter in Spanning Tree protocol?

To ignore BPDUs on specific ports Signup and view all the answers

What happens when a switch sees BPDUs on multiple ports?

It identifies parallel paths and takes action to prevent loops Signup and view all the answers

If two upstream switches have the same cost and the same bridge ID, what is the next tiebreaker used to determine the root port?

The interface's priority Signup and view all the answers

What is the main purpose of the Spanning Tree Protocol?

To prevent network loops by blocking redundant paths Signup and view all the answers

Which of the following statements is TRUE about a designated port in the Spanning Tree protocol?

It is a port that is forwarding traffic away from the root bridge Signup and view all the answers

In the context of the Spanning Tree Protocol, what does a 'blocking state' refer to?

A port that is preventing traffic from passing through it to avoid loops Signup and view all the answers

Why is the root bridge's bridge ID important in the Spanning Tree Protocol?

It is used to establish the hierarchy of the network and guide the path for traffic towards the root bridge Signup and view all the answers

What is the primary reason why a switch might be forwarding traffic on one port but not on another port that connects to the same device?

The Spanning Tree Protocol has determined that the inactive port is redundant and needs to be blocked Signup and view all the answers

What is the role of the 'root port' in a switch that is not the root bridge?

To forward traffic towards the root bridge, creating a path for communication Signup and view all the answers

Which of the following is a key difference between layer 1 hubs and layer 2 switches in relation to the Spanning Tree Protocol?

Hubs do not support the Spanning Tree Protocol, while switches use it to prevent loops Signup and view all the answers

How is the Spanning Tree Protocol able to determine which paths are redundant and should be blocked?

By exchanging Bridge Protocol Data Units (BPDUs) between switches Signup and view all the answers

What is the implication of a switch having a designated port associated with a specific VLAN?

The switch is forwarding traffic for that VLAN away from the root bridge Signup and view all the answers

Study Notes

VLANs and Trunking

Trunking and tagging frames are essential for maintaining traffic separation across VLANs, ensuring broadcasts remain confined to individual VLANs.
Multiple connections between switches (fiber and copper) can introduce the risk of Layer 2 loops in networking.

Spanning Tree Protocol (STP)

STP is implemented by most commercial switches (e.g., Cisco, HP, Juniper) to prevent Layer 2 loops and manage parallel paths.
The protocol identifies and disables one of the parallel paths, allowing only one active link to prevent broadcast storms.
BPDUs (Bridge Protocol Data Units) are exchanged between switches to facilitate loop prevention and election of the root bridge.

Root Bridge

The root bridge is determined by the lowest bridge ID among switches, with its ports forwarding traffic.
All ports of the root bridge for a given VLAN are designated ports, forwarding away from the root.

Election Process

When two switches compete for root bridge status, they send BPDUs comparing their bridge IDs (combination of priority and MAC address).
The switch with the lowest bridge ID becomes the root bridge, while the other switch is considered a non-root bridge, which will identify its best path (root port) to the root.

Non-Root Bridge Behavior

Each non-root switch has exactly one root port used for forwarding to the root bridge.
Other ports leading towards the root are placed in a blocking state to prevent loops, thus allowing only one forwarding path per VLAN.

Forwarding and Blocking States

In a typical scenario, a switch will forward traffic through its root port and block any additional links that may introduce redundancy.
Designated ports on non-root switches forward traffic away from the root bridge.

Security Measures in STP

Root Guard: Prevents switches from accepting higher bridge IDs that could alter the root bridge status.
BPDU Guard: Disables ports that receive unexpected BPDUs, preventing unauthorized influence on the network.
BPDU Filter: Ignores incoming BPDUs on specific ports to avoid processing unauthorized messages.

Limitations of STP

STP can limit bandwidth by disabling one link in a multi-link connection; it operates on the principle of redundancy prevention rather than maximizing throughput.

Advanced Techniques

Link aggregation can be utilized to combine multiple physical connections into a single logical link while avoiding loops, thereby enhancing bandwidth without compromising network integrity.

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Description

Learn how to set up trunking and tagging of frames between switches to ensure broadcast traffic stays within a VLAN. This video explains the importance of separating traffic and challenges of multiple connections between switches.