Router Configuration and Modes

Router Configuration Modes

• User Mode:
  • Identified by Router> prompt.
  • Command to enter: enable (or en).
• Privilege Mode:
  • Identified by Router# prompt.
• Configuration Terminal Mode:
  • Command to enter: config t.
  • Used for configuring router settings.
• Configuration Interface Mode:
  • Enter by specifying an interface (e.g., interface fastEthernet 0/0).
  • Used to configure specific interfaces.

Configuring a Fast Ethernet Interface

1. Enter configuration interface mode: interface fastEthernet f0/0.
2. Assign an IP address with subnet mask: ip address <ip_address> <subnet_mask>
   • Example: ip address 10.0.0.1 255.0.0.0
3. Enable the interface: no shutdown.

Default Gateway

• The router's IP address on the LAN.
• Configured on computers to allow them to communicate outside their local network.
• Example: 10.0.0.1 (configured on the router's fast Ethernet interface).

Configuring IP Address on Computer

1. Go to desktop.
2. Select IP configuration.
3. Choose the "Static" tab.
4. Enter IP address, subnet mask, and default gateway.

Router Configuration Methods

• GUI Method:
  1. Click on "Config" tab.
  2. Select the interface to configure.
  3. Set port status to "On".
  4. Enter IP address and subnet mask.
  • Equivalent CLI commands run automatically.
• CLI (Command Line Interface) Method:
  1. Access CLI.
  2. When prompted to enter initial configuration dialog, type no.

CLI Configuration Steps

1. Enter enable mode: enable (or en).
2. Enter configuration terminal mode: config t.
3. Select the interface: interface fastEthernet 0/0.
4. Assign IP address and subnet mask: ip address 10.0.0.1 255.0.0.0.
   • If an invalid input error occurs, ensure proper spacing in the command.
5. Activate the interface: no shutdown.

Connectivity Check

• Use the ping command to check reachability.
  • Example: ping 10.0.0.2 (from the router to the computer).

Router Initial Configuration Dialog

• When the router boots, it asks: "Would you like to enter the initial configuration dialog?"
• Answer no to configure manually.
• Answering yes leads to a series of questions that may be unfamiliar.

Command Assistance

• Use the question mark ? to get help and see available commands.
  • Example: interface ? shows available interface types.

Invalid Input Errors

• Occur due to incorrect syntax or incomplete commands.
• Read the error message to identify the problem.

Adding Modules to Routers

• Some routers (e.g., 2620) are modular and require interface cards to be added.
• To add a module:
  1. Power off the router.
  2. Drag the desired module (e.g., NM-4A/S) to an available slot.
  3. Power on the router.

Connecting Two Routers

• Use a serial connection (WAN link).
• Ensure both routers have appropriate serial interface modules installed.

IP Addressing for Multiple Networks

• Routers connect different networks.
• Each interface on a router must have an IP address in a different network.
• Example:
  • Router 1: 10.0.0.1 (connected to LAN 10.0.0.0/8), 30.0.0.1 (connected to WAN)
  • Router 2: 20.0.0.1 (connected to LAN 20.0.0.0/8), 30.0.0.2 (connected to WAN)

Incorrect IP Configuration

• Machines on the same LAN must have IP addresses in the same network.
• Example: If a router's fast Ethernet interface has IP 10.0.0.1, all computers on that LAN must have IPs like 10.0.0.2, 10.0.0.3, etc.
• Trying to connect two computers with different network IDs (e.g., 10.0.0.2 and 20.0.0.2) directly will not work.

Show Running Config

• In privileged mode, the command show run displays the router's current configuration.

Key Takeaways

• Initial configuration dialog.
• Configure at least one computer, one router. Understand each of the modes.
• How to configure it, how to delete the configuration of the routers, where to write the IP address.