Switching, STP, and WANs

• The study notes cover advanced switching concepts, Spanning Tree Protocol (STP), and Wide Area Networks (WAN).

Basic Concepts of Layer 2 Switching

• Layer 2 switching operates at the data link layer of the OSI model.
• MAC addresses are used to forward frames between devices.
• Switches learn MAC addresses of connected devices.
• Switches forward frames based on the MAC address table.

MAC Address Learning

• Switches dynamically learn MAC addresses.
• The MAC table is built and updated as devices send frames.
• If a device moves to another port, the MAC address table is updated.

Introduction to VLANs

• A VLAN is a logical network that groups devices regardless of their physical location.
• VLANs improve network performance, security, and management.
• A physical network can contain multiple VLANs, separating traffic between them.

Assigning VLANs to Switch Ports

• Switch ports can be assigned to access VLANs or trunk VLANs.
• Access ports allow connected devices to belong to one VLAN only.
• Trunk ports allow multiple VLANs to share a link between switches.

Trunk Link Configuration

• Trunk links carry traffic for multiple VLANs.
• The 802.1Q standard tags the frames to identify the VLAN to which they belong.
• Trunk links interconnect switches.

Native VLAN and 802.1Q

• The native VLAN is the default VLAN for untagged traffic.
• The 802.1Q standard adds a VLAN tag to the frames.
• Frames of the native VLAN are not tagged, but those of the other VLANs are.

What is EtherChannel?

• EtherChannel combines multiple physical links into one logical channel.
• It provides greater bandwidth and redundancy.
• EtherChannel is compatible with LACP and PAgP for link negotiation.

EtherChannel Configuration Modes

• On Mode: Manual EtherChannel configuration without negotiation.
• Desirable Mode: The switch tries to form an EtherChannel using PAgP.
• Active Mode: The switch tries to form an EtherChannel using LACP.
• Auto and Passive Modes: Automatic configuration that waits for the other device to start negotiation.

Dynamic Trunking Protocol (DTP)

• DTP is a protocol used to negotiate trunk links between switches.
• DTP can be configured in Desirable, Auto, On, or Nonegotiate mode.

Configuring VLANs: Creation and Assignment

• VLANs are configured by VLAN ID.
• Ports are assigned to VLANs using switchport access vlan.
• Each VLAN has an associated IP address range.

Data VLANs and Voice VLANs

• Data VLAN: For normal network traffic.
• Voice VLAN: To separate voice traffic, guaranteeing quality of service (QoS).

Trunk Link and Native VLAN Configuration

• Trunk links allow traffic from multiple VLANs.
• A native VLAN is assigned for untagged traffic.

Trunk Link Configuration

• 802.1Q tags are used in trunk links to distinguish VLANs.
• Switches can tag the traffic to transmit multiple VLANs over a single link.

EtherChannel: Mode of Operation and Advantages

• EtherChannel combines multiple links into one logical channel.
• It Improves bandwidth and redundancy.

Introduction to Spanning Tree Protocol (STP)

• STPprevents network loops in switched networks.
• It identifies a single active path for traffic.

STP Algorithm

• STP uses the Spanning Tree Algorithm (STA).
• The root bridge is the primary switch in the tree.

STP Port Status: Blocking, Listening, Learning and Forwarding

• Blocking: The port does not send or receive frames.
• Listening: The port listens to frames but does not forward them.
• Learning: The port learns MAC addresses.
• Forwarding: The port actively sends and receives frames.

PortFast Configuration in STP

• PortFast accelerates the port's transition process from blocking to forwarding state.
• It is helpful in ports that connect to end devices such as computers.

BPDU Guard Configuration

• BPDU Guard protects the network from unwanted devices.
• It blocks ports that receive unauthorized BPDUs.

Basic WAN Concepts

• WAN connects geographically dispersed devices.
• MPLS, VPN and Internet protocols are key technologies in WAN.

WAN Topologies

• Point-to-Point, Star, Mesh, and Ring are common WAN topologies.
• Topology selection depends on redundancy and cost.

PPP and Authentication Protocols

• PPP is a point-to-point link protocol.
• PAP and CHAP are authentication methods.

GRE Tunnel Configuration

• GRE enables the creation of secure tunnels between devices.
• Tunnels encapsulate layer 3 protocols (IP, IPX, etc.).

VLAN Trunking Protocol (VTP) Concept

• VLAN Trunking Protocol manages VLAN configuration across a network.
• It reduces the manual configuration of VLANs on multiple switches.

Troubleshooting Practice in STP

• Identification and resolution of common STP problems.
• Diagnostic tools like show spanning-tree can be used to troubleshoot STP

Use of MPLS in WAN

• MPLS (Multiprotocol Label Switching) is an advanced protocol for directing and accelerating data traffic on the network.
• It optimizes routing and reduces latency.

Redundancy in EtherChannel and STP

• EtherChannel provides redundancy without the need for STP.
• STP is still useful for preventing loops in complex networks.

Monitoring VLANs and STP in Large Networks

• Monitoring tools are used to verify network integrity.
• Network management commands and systems (NMS) are valuable.

Security Practices in VLANs and STP

• STP Security: Configuration of BPDU Guard, Root Guard, and Loop Guard to protect the network.
• VLAN Protection: Isolation of critical VLANs.