CCNA | Switch Interfaces | 9

Overview of Switch Interfaces

• Introduction: Shift in focus from IP addresses to switch interfaces.

• Comparison with Router Interfaces:

  • Router interfaces require configuration for activation.

  • Switch interfaces are enabled by default (not requiring a shutdown command).

Key Concepts

Layer 1 Characteristics

• Speed:

  • Defines data rate in bits per second (e.g., 10, 100, or 1000 Mbps).

• Duplex:

  • Determines if devices can send and receive data simultaneously:

    • Half Duplex: Cannot send and receive at the same time.

    • Full Duplex: Can send and receive simultaneously.

• Auto Negotiation:

  • Devices automatically negotiate speed and duplex without manual configuration.

Interface Status

• Understanding Status Indicators:

  • Command show IP interface brief shows layer one (status) and layer two (protocol) states.

  • Typical statuses include:

    • Up/Up: Connected and operational.

    • Down/Down: Not connected to any device.

    • Administratively Down: Manually configured to be disabled.

Interface Counters and Errors

• Interface Statistics:

  • Cisco devices count various traffic statistics:

    • Errors, received packets, and frame issues are monitored.

  • Common counters include:

    • Runs: Frames smaller than 64 bytes.

    • Giants: Frames larger than 1518 bytes.

    • CRC Errors: Frames that fail cyclic redundancy check.

    • Input and Output Errors: Overall error counts.

Differences Between Routers and Switches

• Router Interfaces:

  • Default state is administratively down; requires configuration to activate.

• Switch Interfaces:

  • Default state is up if connected; no manual setup needed for basic operation.

Example Network Configuration

Network Topology

• Single LAN Overview:

  • Network with 1 router (R1), 2 switches (SW1 and SW2), and 4 PCs.

• Focus: Configuring Switch 1 interfaces (F0/1 to F0/4).

Working with Switch CLI

1. Entering Privileged Exec Mode:

   • Use command enable.

2. Checking Interface Status:

   • Command show IP interface brief reveals interface statuses:

     • Connected interfaces report up/up.

     • Not connected interfaces report down/down.

3. Command for Detailed Status:

   • show interfaces status lists:

     • Port names, status, VLANs, duplex, speed, and other interface details.

Manual Configuration of Interfaces

• Configuring Speed and Duplex:

  • Commands used to set speed (10 or 100 Mbps) and duplex (auto, full, half).

  • Example command sequence:

    interface f0/1  
    speed 100  
    duplex full  
    description Connected to R1

• Bulk Configuration:

  • Use interface range command to configure multiple interfaces at once:

    interface range f0/5 - f0/12  
    shutdown

Collision Domains and Duplex Modes

• Half Duplex:

  • Concept of collision domains; devices cannot send and receive simultaneously.

  • Example usage with hubs.

• Full Duplex:

  • Modern switches operate in full duplex, eliminating collisions.

Auto Negotiation Process

• Understanding Auto Negotiation:

  • Both routers and switches support automatic speed and duplex negotiation.

  • Example scenarios clarifying how devices respond based on settings.

Conclusion and Review

• Key points covered include:

  • Differences in switch vs. router interfaces regarding activation and default states.

  • Importance of speed and duplex settings for network performance.

  • Interface monitoring via show command statistics.

• Prepare for upcoming quiz on concepts discussed.