How to Upgrade Cisco IOS Software in a Router or a Switch
Upgrading IOS on buy cisco routers and switches is highly recommendable because of the following reasons
Patch critical vulnerabilities: Just like any other network device or application, Cisco routers and switches are also prone to security holes. And because routers and switches are critical to network infrastructure, you should plug these security holes as soon as possible.
Incorporate new features: Unless an update is simply a bug fix, every new release of the Cisco IOS includes new features. Upgrading your buy used router and switches in a timely manner means youll have more features to potentially make your job easier.
Stay current: Staying current with the latest IOS may sound like a flimsy justification to upgrade, especially when you consider your daily task list. However, when you consider the many different tools that communicate with the routers IOS, staying current can take on a new importance. For example, if youre using a SNMP network management tool, it may require your router to run a certain version of the IOS.
Procedure to upgrade cisco IOS NOTE:Before doing any upgrades plesae take a complete backup of your cisco device configuration for safer side
Download the Correct version of Cisco IOS for you from here
Write Unsaved configurations
ciscorouter# write memory Building configuration [OK]
Check space on Flash Memory
ciscorouter# show flash
Make sure you have the space left on your cisco device.
Backup Startup Configuration
Setup a TFTP server in the same IP range as the refurbished cisco router device to backup the configs, IOS image and also for later to upload the new IOS image.
testrouter# copy startup-configtftp Address or name of remote host []? 10.10.10.2 Destination filename [startup-config]? !! 1278 bytes c opied in 0.100 secs
Backup Current IOS Image
testrouter# copy flash: tftp: Source filename []?xxxxx-xx-xx.121-x.XB Address or name of remote host []? 10.10.10.2 Destination filename [xxxxx-xx-xx.121-x.XB]?
Now, Load the new IOS image from the TFTP onto the flash
ciscorouter#copytftp: flash: Address or name of remote host []? 10.10.10.2 Source filename []?c3560-ipbasek9-mz.122-40.SE.bin Destination filename [c3560-ipbasek9-mz.122-40.SE.bin]? Accessing tftp://10.10.10.2/c3560-ipbasek9-mz.122-40.SE.bin Loading c3560-ipbasek9-mz.122-40.SE.bin from 10.10.10.2 (via Vlan1): !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!! [OK - 8295106 bytes]
8295106 bytes copied in 124.571 secs (66589 bytes/sec)
Now you need to make sure you are booting with the correct version of IOS image for this you need to use the following command to set.
testrouter(config)#boot system flash:/c3560-ipbasek9-mz.122-40.SE.bin
