Hands-On Lab: Backing Up and Restoring Router Configuration Files

Lab Objective

Back up a router's current configuration to a TFTP server, make a deliberate unwanted change to the configuration, then restore the router to its previously backed-up state and verify the unwanted change is gone.

Lab Purpose

A configuration backup taken before a risky change is standard practice before any significant maintenance activity, providing a fast, reliable way to revert if something goes wrong rather than manually reconstructing a configuration from memory or scattered notes.

Lab Topology

R1 ---- Gi0/0: 192.168.85.1/24

TFTP server: 192.168.85.100/24

Task 1: Configure Basic Addressing

Configure R1's interface connecting to the TFTP server's segment.

Task 2: Back Up the Current Configuration

Copy R1's running configuration to the TFTP server.

Task 3: Make an Unwanted Configuration Change

Deliberately change R1's hostname and remove a loopback interface, simulating an unintended or mistaken configuration change.

Task 4: Verify the Unwanted State

Confirm the hostname has changed and the loopback interface is gone.

Task 5: Restore from the Backup

Copy the backed-up configuration from the TFTP server back onto R1.

Task 6: Verify the Restoration

Confirm the hostname and loopback interface match the original backed-up state.

Solution and Verification

R1(config)# interface gigabitethernet0/0
R1(config-if)# ip address 192.168.85.1 255.255.255.0
R1(config-if)# no shutdown
R1(config-if)# exit
R1(config)# interface loopback0
R1(config-if)# ip address 10.99.1.1 255.255.255.255
R1(config-if)# exit
R1(config)# end

R1# copy running-config tftp:

Address or name of remote host []? 192.168.85.100
Destination filename [r1-confg]? R1-backup.txt

Writing R1-backup.txt !!
1284 bytes copied in 1.294 secs

R1(config)# hostname R1-BROKEN
R1-BROKEN(config)# no interface loopback0
R1-BROKEN(config)# end

R1-BROKEN# show ip interface brief | include Loopback
-- (no output -- loopback0 is gone)

R1-BROKEN# show running-config | include hostname
hostname R1-BROKEN

R1-BROKEN# copy tftp: running-config

Address or name of remote host []? 192.168.85.100
Source filename []? R1-backup.txt
Destination filename [running-config]?

Accessing tftp://192.168.85.100/R1-backup.txt...
Loading R1-backup.txt from 192.168.85.100
1284 bytes copied in 1.156 secs

R1# show running-config | include hostname
hostname R1
-- Hostname restored

R1# show ip interface brief | include Loopback
Loopback0    10.99.1.1    YES manual up    up
-- Loopback interface restored

Key Takeaway

Restoring from a backup with copy tftp: running-config merges the backup into the currently running configuration rather than fully replacing it — any configuration added after the backup was taken but not present in the backed-up file may still remain, so verifying the final state after a restore, as done here, is essential rather than assuming a restore perfectly recreates the exact backed-up state.