1. Install tftpd software on your machine
   
2. connect using a USB to serial cable to the switch (9600,8.n.1)
   
3. wait for it to boot
   
4. check for the installed ios version
   
5. sh version 
   
6. Now you need to configure an IP address for your switch that resides on the same broadcast domain as your machine will be
   
7. conf t
   
8. int vlan 225
   
9. IP address 10.10.10.100 255.255.255.0
   
10. exit
    
11. end
    
12. sh IP interface vlan 225 
    
13. now activate the vlan interface and associate it to a port of the switch
    
14. conf t
    
15. interface vlan 225
    
16. no shut
    
17. exit
    
18. interface gigabitethernet 1/0/1
    
19. switchport access vlan 225
    
20. no shut
    
21. exit
    
22. end
    
23. verify that the interface is up and running with the specified IP address
    
24. sh interface gigabitethernet 1/0/1 status
    
25. sh ip interface brief 
    
26. Now try to ping the host running the tftp server and ensure that network communication is ok
    
27. then run the following command to backup the current version of the flash
    
28. dir flash:
    
29. copy flash: tfp:
    
30. enter the source file name, for example : c3750-ipbasek9-mz.122-55.SE11.bin
    
31. enter the tftp server ip address : 10.100.0.99
    
32. then wait for the copy finish
    
33. when finished run
    
34. delete /force /recursive c3750-ipbasek9-mz.122-55.SE11.bin
    
35. check for the file you need to copy from the tftp server and run
    
36. copy tftp: flash:
    
37. enter the c3750-ipbasek9-mz.150-2.SE11.bin name
    
38. and wait for it to be copied to the flash
    
39. now check for the boot file
    
40. sh boot 
    
41. as you can see the file is the old one, you need to change it running the following commands
    
42. conf t
    
43. boot system switch all flash:c3750-ipbasek9-mz.150-2.SE11.bin
    
44. reload the switch and check for the updated version