Module 3: Configuring Interfaces and Switches

Module 3: Configuring Interfaces and Switches

• This module covers networking devices, interfaces, Ethernet switching features, and transceiver switching issues.
• Learning objectives include deploying networking devices, explaining network interfaces, deploying Ethernet switching features, and troubleshooting transceiver switching issues.

Lesson 3.1: Network Interfaces

• Network interfaces act as a connection point for a host to a transmission medium (wired or wireless).
• Network Interface Cards (NICs) are a key component of network interfaces, housing the transceiver component.
• A NIC can have multiple ports on the same card.
• A unique MAC address identifies each NIC.
• NICs operate at the Data Link layer of the OSI model.

Symptoms of NIC Issues

• Common symptoms of NIC problems include network connectivity failure, slow network speeds, intermittent connectivity, and error messages (device manager or network settings).

Modular Transceivers

• Modular transceivers support different cable and connector types.
• They operate at the Data Link layer.

Symptoms of Transceiver Issues

• Mismatched ports can lead to no link or intermittent connection loss.
• Signal strength issues may cause intermittent connections, packet loss, and poor network performance.

Ethernet Frame Format

• The Ethernet frame consists of multiple parts: preamble (7 bytes), start frame delimiter (SFD), destination MAC address, source MAC address, Ethernet Type, payload, and frame check sequence (FCS).
• Preamble synchronizes devices.
• SFD indicates the start of the frame.
• Source and destination MAC addresses identify sending and receiving devices.
• Ether Type specifies the protocol of the payload.
• Payload carries data.
• FCS verifies data integrity.

MAC Address Format

• A MAC address is a unique identifier for a network interface card (NIC)
• It's a 48-bit alphanumeric identifier (pairs of hexadecimal digits separated by colons or hyphens).
• The first few bytes (OUI) define the organization associated with the device's manufacturer.

MAC Broadcast Address

• A MAC broadcast address (all 1s) targets all devices on a network.
• All devices on the network receive and process a packet with a broadcast address.

Lesson 3.2: Ethernet Switches

• Hubs send transmissions from one port to every other port.
• Bridges separate physical network segments while maintaining a logical network.
• Switches send transmissions from one port only to the destination port. They are more efficient than hubs by reducing network congestion.

Ethernet Switch Types

• Unmanaged: Have limited configuration options.
• Managed: Offer configuration settings for enhanced management.
• Modular: Offer different port numbers and types.
• Fixed: Have a fixed number of ports.
• Desktop: Freestanding switches.
• Rack: Designed to fit into networking racks.
• Stackable: Multiple switches can be connected as a single unit.

Activity: Matching

• Hub: Operates primarily at the physical layer.
• Switch: Intelligently directs data to a specific port based on MAC addresses, reducing network congestion and improving efficiency by dividing a network into smaller, manageable sections.
• Bridge: Improves network efficiency by dividing it into smaller, manageable sections.

Lesson 3.3: Switch Port Configuration

• Link Aggregation/NIC Teaming: Combines multiple links into a single logical channel, offering redundancy and cost-effectiveness.

Maximum Transmission Unit (MTU)

• Standard Ethernet frames have a maximum transmission unit (MTU) of 1,500 bytes.
• Jumbo frames allow larger payloads (up to 9216 bytes) but are not compatible with all Ethernet standards.

Spanning Tree Protocol (STP)

• A Layer 2 protocol that prevents bridge loops and provides fault tolerance by creating a single, optimal path.

Power over Ethernet (PoE)

• Allows transmitting both data and power through a single cable.
• Facilitates network installation and expansion.

Lesson 3.4: Switch Troubleshooting

Hardware Failure Issues

• Power Issues: Verify stable power supply, install UPS (uninterruptible power supply), check for damaged ports/connectors, and check the drivers.
• Network Adapters: Visually inspect for damage, check indicator lights, inspect power supply and wiring connections, and restart the device to resolve issues.
• Switches/Routers/Modems: Visually inspect for damage, check indicator lights, and verify power supply/cabling connections and update or reinstall drivers.
• Overheating: Check for proper ventilation, remove dust, and ensure cooling systems are functional.

Port Status Indicators

• Solid green: Link is connected, no traffic.
• Flickering green: Link is operating normally, with traffic.
• No light: Link is not working, or the port is shut down.
• Solid amber: Port is blocked by the spanning tree algorithm.
• Blinking amber: Fault detected.

Switch Show Commands

• Show config: Displays current switch configuration.
• Show startup-config: Shows the configuration used after a reset.
• Show running-config: Shows the actively running switch configuration.
• Show interface: Provides detailed information about the switch's interfaces.

Switch Show Command Status

• Down/down: Layer 1 (physical) and Layer 2 (data link) connections are inactive. The interface is manually disabled or is experiencing a network error.
• Down/error disabled: The interface is disabled due to a network error or policy violation.
• Up/down (suspended): Physical layer is operational, inactive data link layer due to admin settings or errors.

Interface Error Counters

• Link state: Checks if the interface is up or down, alerting for downtime.
• Resets: Monitors manual and automatic restarts, with high frequencies requiring attention.
• Discards/drops: Detects and reports issues with checksum errors, mismatch MTUs, size anomalies, high load, or ACL/VLAN errors, aiding in troubleshooting.

Common Interface Errors

• Cyclic Redundancy Check (CRC) errors: Indicate noise, interference, or equipment malfunctions.
• Runt Frame errors: Frames smaller than the minimum size, often due to collisions or damaged hardware.
• Giant Frame errors: Frames exceeding the maximum size, usually caused by misconfiguration or malfunctions.

Network Loop and Broadcast Storm

• Network Loops: Caused by redundant connections or end-device issues. Solutions include proper configuration of redundant connections and implementing STP.
• Broadcast Storms: Caused by DHCP issues or oversized broadcast domains. Solutions include monitoring DHCP traffic and segmenting the network.

Power Over Ethernet Issues

• Cabling: Requires Cat 5e or better (Cat6A recommended). Thick conductor is important (23 AWG or better). Shielded cables help efficiently disperse heat.
• Standard Compatibility: Devices necessitate correct PoE mode (alternative A, B, or Four-pair); challenging devices may only support the first standard.
• Power Budget Management: Switches have limited budget (300-400W). The "show power inline" command monitors the budget.

Activity: What Would You Do?

• (Example/Placeholder) Identify the problem, Check power source/connections, Check cables and connections, and check the device switch configuration.