Module 3: Configuring Interfaces and Switches

Module 3: Configuring Interfaces and Switches

• This module focuses on networking devices, network interfaces, Ethernet switching, and transceiver switching troubleshooting.

Learning Objectives

• Deploy networking devices.
• Explain network interfaces.
• Deploy common Ethernet switching features.
• Troubleshoot transceiver switching issues.

Lesson 3.1: Network Interfaces

• Network Interface Cards (NICs):

  • A crucial component.
  • Connects a host to a transmission medium (wired or wireless).
  • Can have multiple ports on a single card.
  • Operates at the Data Link layer.
  • Each NIC has a unique Media Access Control (MAC) address.

• Symptoms of NIC Issues:

  • Network connectivity failure.
  • Slow network speeds.
  • Intermittent connectivity problems.
  • Device manager error messages.
  • Network setting error messages.

Modular Transceivers

• Allows termination of multiple cable and connector types.
• Operate at the Data Link layer.

Symptoms of Transceiver Issues

• Mismatched ports:
  • No link.
  • Intermittent connection loss.
• Signal strength problems:
  • Intermittent connections.
  • Packet loss.
  • Poor network performance.

Ethernet Frame Format

• Preamble (7 Bytes): Synchronization sequence.
• Start Frame Delimiter (SFD) (1 Byte): Signals the start of the frame.
• Destination MAC Address (6 Bytes): Address of the recipient device.
• Source MAC Address (6 Bytes): Address of the sending device.
• Ether Type (2 Bytes): Protocol of the payload.
• Payload (46-1500 Bytes): Data being transmitted.
• Frame Check Sequence (FCS) (4 Bytes): Error-checking code.

MAC Address Format

• Consists of an Organizationally Unique Identifier (OUI).
• Composed of 48-bit alphanumeric identifiers.
• Pairs of hexadecimal digits separated by colons or hyphens.

MAC Broadcast Address

• All bits set to 1 (e.g., FF:FF:FF:FF:FF:FF).
• All hosts on the network receive and process the packet addressed to this.

Lesson 3.2: Ethernet Switches

• Hubs: Transmit transmissions from one port to every other port.
• Bridges: Separate physical network segments while maintaining a common logical network.
• Switches: Transmit transmissions from one port only to the destination port (based on MAC addresses).

Ethernet Switch Types

• Unmanaged: No configuration options.
• Managed: Configurable switches.
• Modular: Configurable with different numbers and types of ports
• Fixed: Come with a fixed number of ports.
• Desktop: Free-standing.
• Stackable: Can be connected together as one unit.

Activity: Matching

• Matching tasks relating to the characteristics and functionalities of hubs, switches, and bridges.

Lesson 3.3: Switch Port Configuration

• Link Aggregation/NIC Teaming: Combines two or more separate cable links to create a single logical channel to improve redundancy and cost-effectiveness.
• Maximum Transmission Unit (MTU): Standard Ethernet frame MTU size is 1,500 bytes.
• Jumbo Frames: Support payloads up to 9,216 bytes, reducing transmitted frames.

Lesson 3.4: Switch Troubleshooting

• Hardware Failure Issues:

  • Power issues: Verify stable power, use UPS, check connections.
  • Network adapters: Check for damage, test alternative devices, install drivers.
  • Switches/Routers/Modems: Visual inspection, power supply verification, cabling connection verification.
  • Overheating: Check ventilation, remove dust, ensure cooling systems are operational.

• Port Status Indicators:

  • Solid green: Link connected, no traffic.
  • Flickering green: Link operational, with traffic.
  • No light: Link or port not functioning.
  • Solid amber: Port blocked by Spanning Tree Algorithm.
  • Blinking amber: Fault detected.

Switch Show Commands

• Show config: Displays the current configuration.
• Show startup-config: Shows the configuration that the device will use after restarting.
• Show running-config: Shows the active configuration of the device.
• Show interface: Displays in-depth information about the device's network interfaces.

Switch Show Command Status

• Down/down: Both layer 1 and layer 2 connections are inactive.
• Administratively Down/Down: Interfaced administratively disabled.
• Down/Error disabled: Interface automatically disabled due to network error or policy violation.
• Up/down (suspended): Physical, layer 1 is operational, but layer 2 is inactive.

Interface Error Counters

• Link state: Checks if the interface is up or down.
• Resets: Counts manual and automatic interface restarts.
• Discards/Drops: Caused by checksum errors, mismatched MTUs, size/high-traffic, ACL or VLAN config errors.

Common Interface Errors

• Cyclic Redundancy Check (CRC) Errors: Frame's checksum mismatch.
• Runt Frame Errors: Frames shorter than the minimum frame size.
• Giant Frame Errors: Data frames exceeding the maximum size.

Network Loops and Broadcast Storms

• Network Loops: Redundant connections, end-device side.
• Network Loops - Solutions: Proper redundant configuration, implement spanning tree protocol (STP), educate users.
• Broadcast Storms - Causes: DHCP issues, very large broadcast domains.
• Broadcast Storms - Solutions: Monitor DHCP traffic, segment the network.

Power Over Ethernet (PoE) Issues

• Cabling Considerations: Cat 5e or better cables, conductor thickness (23 AWG or better), shielded cabling.
• Standard Compatibility: Device must negotiate correct PoE mode (Alternative A, B, or Four-pair). Challenges with devices only supporting the first PoE standard.
• Power Budget Management: Switches have a limited power budget (300-400W). Use "show power inline" command for monitoring.

Activity: What Would You Do?

• Troubleshooting steps when a switch fails to power on.

Summary

• NIC vs. Transceiver: NIC connects to the network, while the transceiver adapts cable types.
• Hub vs. Switch: Hub broadcasts, switch directs.
• Spanning Tree Protocol (STP): Prevents bridge loops, ensures network redundancy.