Table of Contents
Configuring Interfaces
These blog posts I created to help me as a reference tool, as well as a way of retaining the knowledge. If you find it useful that’s just a plus.
Configuration Commands
Interface
Changes from global configuration mode to interface configuration mode, allowing you to configure the specified interface.
Syntax:
interface Serial 0/0/0
Example:
Router1>enable
Router1#configure terminal
Router1(config)#interface GigabitEthernet0/1
Router1(config-if)#
IP Address
Assigns an IP address and subnet mask to an interface.
Syntax:
ip address [ip-address] [subnet-mask]
Example:
Router1>enable
Router1#configure terminal
Router1(config)#interface GigabitEthernet0/1
Router1(config-if)#ip address 10.1.1.1 255.255.255.0
No Shutdown
Enables an interface that was previously disabled.
Syntax:
no shutdown
Example:
Router1>enable
Router1#configure terminal
Router1(config)#interface GigabitEthernet0/1
Router1(config-if)#ip address 10.1.1.1 255.255.255.0
Router1(config-if)#no shutdown
Description
Assigns a description to an interface for easy identification.
Syntax:
description [description]
Example:
Router1>enable
Router1#configure terminal
Router1(config)#interface GigabitEthernet0/1
Router1(config-if)#ip address 10.1.1.1 255.255.255.0
Router1(config-if)#description Link to HQ
Hostname
Sets the device name (hostname) for easier identification of the router.
Syntax:
hostname [hostname]
Example:
Router1>enable
Router1#configure terminal
Router1(config)#hostname Router2
Router2(config)#
Interface Management
Clock Rate
Sets the clock rate for a Data Communications Equipment (DCE) interface.
Syntax:
clock rate [clock-rate]
Example:
Router1>enable
Router1#configure terminal
Router1(config)#interface GigabitEthernet0/1
Router1(config-if)#clock rate 128000
IP Host
Configures a static hostname-to-address mapping in the host cache of a device.
Syntax:
ip host [host-name] [ip-address]
Example:
Router1>enable
Router1#configure terminal
Router1(config)#ip host Webserver 172.16.0.1
Verification and Monitoring
Show IP Interface
Displays IP information for a specified interface.
Syntax:
show ip interface [interface] [interface-number]
Example:
Router1>enable
Router1#show ip interface GigabitEthernet 0/1
Show IP Interface Brief
Displays a brief summary of interface status and configuration.
Syntax:
show ip interface brief
Example:
Router1>enable
Router1#show ip interface brief
Show Running-Config
Displays the active configuration file, allowing you to verify interface settings.
Syntax:
show running-config
Example:
Router1>enable
Router1#show running-config
Show Controllers
Displays cable orientation for Serial interfaces.
Syntax:
show controllers [type number]
Example:
Router1>enable
Router1#show controllers Serial 0/0/0
Show Interfaces
Displays statistics for all interfaces configured on the router.
Syntax:
show interfaces [type number]
Example:
Router1>enable
Router1#show interfaces Serial 0/0/0
Ping
Sends an Internet Control Message Protocol (ICMP) echo request to the specified address to test connectivity.
Syntax:
ping [ip-address]
Example:
Router1>ping 8.8.8.8
EVE-NG Lab
In this lab, we will configure router interfaces using a simple topology that involves three routers (Router1, Router2, and Router3) connected via serial interfaces. The lab will cover configuring IP addresses, verifying connectivity with the ping command, and using the show commands to gather information about the interface configuration.
| Device | Interface | IP Address | Subnet Mask |
|---|---|---|---|
|
Router1 |
S0/0/0 |
10.1.1.1 |
255.255.255.0 |
|
Router2 |
S0/0/0 |
10.1.1.2 |
255.255.255.0 |
|
Router2 |
S0/0/1 |
172.16.10.2 |
255.255.255.0 |
|
Router3 |
S0/0/0 |
172.16.10.1 |
255.255.255.0 |
Configuring IP Addresses
Router1
Enter global configuration mode:
Router1>enable
Router1#configure terminal
Configure the IP address for S0/0/0 interface:
Router1(config)# interface Serial 0/0/0
Router1(config-if)# ip address 10.1.1.1 255.255.255.0
Router1(config-if)# no shutdown
Verify the configuration:
Router1(config-if)#do show ip interface brief
Exit the interface configuration mode:
Router1(config-if)# exit
Router2
Enter global configuration mode:
Router2>enable
Router2#configure terminal
Configure the IP address for S0/0/0 interface:
Router2(config)# interface Serial 0/0/0
Router2(config-if)# ip address 10.1.1.2 255.255.255.0
Router2(config-if)# no shutdown
Configure the IP address for S0/0/1 interface:
Router2(config)# interface Serial 0/0/1
Router2(config-if)# ip address 172.16.10.2 255.255.255.0
Router2(config-if)# no shutdown
Verify the configuration:
Router2(config-if)#do show ip interface brief
Exit the interface configuration mode:
Router2(config-if)# exit
Router3
Enter global configuration mode:
Router3>enable
Router3#configure terminal
Configure the IP address for S0/0/0 interface:
Router3(config)# interface Serial 0/0/0
Router3(config-if)# ip address 172.16.10.1 255.255.255.0
Router3(config-if)# no shutdown
Verify the configuration:
Router3(config-if)#do show ip interface brief
Exit the interface configuration mode:
Router3(config-if)# exit
Verifying Connectivity
All Routers
After configuring the IP addresses, it’s essential to verify that each router can reach the others by using the ping command.
Router1>enable
Router1#ping 10.1.1.2
Router2>enable
Router2#ping 10.1.1.1
Router2#ping 172.16.10.1
Router3>enable
Router3#ping 172.16.10.2
Display detailed information:
Router>enable
Router#show cdp neighbors detail