Upgrading IOS Version
You will need a tftp server on which to put the latest IOS version and to which to can backup the old one. A Windows based one is easy . This assumes that the switch already has an IP set, otherwise follow this link . Below works for Catalyst 29XX and 37XX models. For Catalyst 49XX models, change flash to bootflash.
1. Determine the boot image on the switch:
switch# show flash
2. Backup the flash image to the tftp server
switch# copy flash:flashimagename tftp://192.168.X.X/flashimagename
where 192.168.X.X is the IP address of the TFTP server.
3. If there is room, leave the old image in place. Otherwise do OPTIONAL and DANGEROUS:
switch# delete flash:imagename
If the flash image is in a directory:
switch# delete /force /recursive flash:flashdirectory
4. Upload the new flashimage
switch# copy tftp://192.168.X.X/newflashimage flash:newflashimage
5. Make the new image the boot image and reboot
switch# config t switch(config)# no boot system flash:oldflashimage switch(config)# boot system flash:newflashimage switch(config)# exit switch# wr mem
6. Reboot the switch