Module 10: Basic Router Configuration - In-depth Notes

Module Objectives

  • Title: Basic Router Configuration
  • Objective: Implement initial settings on a router and end devices.

Configure Initial Router Settings

  • Configure initial settings on an IOS Cisco router including:
    • Device name
    • Privileged EXEC mode security
    • User EXEC mode security
    • Remote Telnet/SSH access security
    • Encryption of plaintext passwords
    • Legal notification and save configuration.
Basic Router Configuration Steps
  • Commands to configure the devices:
    • Router(config)# hostname <hostname>
    • Router(config)# enable secret <password>
    • Router(config)# line console 0
    • Router(config-line)# password <password>
    • Router(config-line)# login
    • Router(config)# line vty 0 4
    • Router(config-line)# password <password>
    • Router(config-line)# login
    • Router(config-line)# transport input {ssh | telnet}
    • Router(config)# service password encryption
    • Router(config)# banner motd # <message> #
    • Router(config)# end
    • Router# copy running-config startup-config
Basic Router Configuration Example
  • Example commands for a router R1:
    • R1(config)# hostname R1
    • R1(config)# enable secret class
    • R1(config)# line console 0
    • R1(config-line)# password cisco
    • R1(config-line)# login
    • R1(config-line)# line vty 0 4
    • R1(config-line)# password cisco
    • R1(config-line)# login
    • R1(config-line)# transport input ssh telnet
    • R1(config-line)# exit
    • R1(config)# service password encryption
    • R1(config)# banner motd # Enter TEXT message. End with a new line and the #
    • R1(config)# exit
    • R1# copy running-config startup-config

Configure Interfaces

  • Commands to configure a router interface:
    • Router(config)# interface <type-and-number>
    • Router(config-if)# description <description-text>
    • Router(config-if)# ip address <ipv4-address> <subnet-mask>
    • Router(config-if)# ipv6 address <ipv6-address>/<prefix-length>
    • Router(config-if)# no shutdown
  • Description command adds clarity on network connections. The no shutdown command activates the interface.
Example Interface Configuration
  • Configure interface G0/0/0 on R1:
    • R1(config)# interface gigabitEthernet 0/0/0
    • R1(config-if)# description Link to LAN
    • R1(config-if)# ip address 192.168.10.1 255.255.255.0
    • R1(config-if)# ipv6 address 2001:db8:acad:10::1/64
    • R1(config-if)# no shutdown
  • Output will show link state and protocol status:
    • %LINK-3-UPDOWN: Interface GigabitEthernet0/0/0, changed state to down
    • %LINK-3-UPDOWN: Interface GigabitEthernet0/0/0, changed state to up

Verify Interface Configuration

  • Use following commands to verify interface settings:
    • show ip interface brief
    • show ipv6 interface brief
Summary of Verification Commands
CommandDescription
show ip interface briefDisplays all interfaces, their IPs, and current status.
show ipv6 interface briefSimilar to IPv4 but for IPv6 interfaces.
show ip routeDisplays the IP routing table stored in RAM.
show ipv6 routeDisplays the IPv6 routing table.
show interfacesDisplays statistics for all interfaces.
show ip interfacesDisplays IPv4 statistics for all interfaces.
show ipv6 interfacesDisplays IPv6 statistics for all interfaces.

Configure the Default Gateway

  • Default Gateway: Used when a host sends packets to a different network.
  • The gateway address is typically the router interface connected to the local network.
Default Gateway Configuration
  • On a host needing to send to another network, use:
    • ip default-gateway <ip-address> for switches.

Conclusion

  • Recap of tasks completed when configuring initial settings:

    • Device name, EXE mode security, remote access security, password encryption, notifications, and configuration save.

  • Reminder: To reach external networks, routers must be configured, and interfaces activated with the no shutdown command.

  • Importance of verifying interface configurations and ensuring default gateways are set correctly to ensure connectivity across different networks.