Updating IOS On Cisco Switch or Router

Exact command entries written in {This format}

Updating an IOS on a Cisco Switch/Router using TFTP

1. Install PuTTy or a similar Telnet application to be able to access the Switch/Router (S/R) through an ethernet connection.
2. Install SolarWinds TFTP server or similar TFTP application to be able to send the IOS image to the S/R.
3. Configure TFTP with the correct IP address (192.168.0.0/24) and change your computer’s ethernet interface adapter the right address range. (Verify the adapter appears in TFTP)
   

   IP configuration for the TFTP server.
   

   IP configuration for the PC interface.
4. Ensure that the correct IOS images are installed on your computer in the designated TFTP folder. (IOS images will have different names from the one pictured below.)
   

   Verification of IOS Images (May be DIFFERENT depending on when you are updating.)
5. Use a computer with a serial cable or similar console connection (COM1) in order to connect to the console port on the S/R.
   

   COM1 Connection using Tera Term (Serial).
6. Enter privileged executive mode and verify the Flash: filesystem has enough space for the new image. {#show flash:}
   

   Verify Flash: directory size and current IOS while In privileged executive.
7. Configure the S/R as follows:
   • Enter configuration terminal mode.
   • Configure the console and vty lines (0 4) for remote access to the S/R. (Use password Cisco to make things easy.)
   • {#config t --> (c)#line con 0 --> (c-line)#password cisco --> (c-line)#login --> (c-line)#logging syn --> (c-line)#line vty 0 4 --> (c-line)#password cisco --> (c-line)#login --> (c-line)#logging syn}
     

     Line console and vty 0 4 configurations.
   • Configure the appropriate IP on the VLAN1/Interface (192.168.0.0/24 Network).
   • Exit back to privileged executive mode. {(c)#int vlan 1 --> (c-if)#ip address 192.168.0.2 255.255.255.0 --> (c-if)#no shut --> (c-if)#end}
     

     IP address configuration on a switch (Will be an INTERFACE on a router).
   • Clear the Flash: filesystem (This takes several minutes and it might seem frozen at first, it is working, I promise.) {#erase flash:}
     

     Erasure of Flash: filesystem.
8. Use a telnet connection over ethernet on your computer to connect to the address configured on the S/R.
   

   IP connection to the S/R using Tera Term (Telnet).
9. Start the TFTP server.
   

   A running TFTP server.
10. Enter commands to send a TFTP file over the connection. (Using the computer address as the source. The filename of the IOS must also be EXACT.) {#copy tftp flash --> host []? 192.168.0.1 --> S filename []? c3750-ipservicesk9-mz.122-55.SE9.bin --> D filename []? (Just hit enter)}
    

    Commands used to copy 3750 IOS to a switch.
11. After the install has finished verify the file is now on the S/R. {#show flash:}
    

    Verification of correct image in Flash: filesystem.
12. Reload the S/R and do not save the configuration. {#reload}
    

    Reloading S/R without saving.
13. Wait for the reboot and verify that the S/R is a blank configuration with the correct IOS installed in Flash:.

Updating an IOS on a Cisco Switch/Router Using HyperTerminal

ROMMON COMMANDS ARE DIFFERENT FROM REGULAR CLI FOR S/R. CHECK YOUR SYNTAX.

1. So you’re the idiot that reloaded an S/R without an IOS on the flash and it only boots into ROMMON? (i.e. switch: )
2. Install HyperTerminal using a Windows XP disc. (Find instructions on how here.)
3. Connect to the S/R using a console connection over COM1 (Run the .exe file to access HyperTerminal (HT). BAUD rate may also be an issue. The usual default is 9600 bits/sec. If the connection is not working try matching the default BAUD rate of the S/R and, if you want it to be faster, then use CONFREG command to change the rate (Higher rates may run into problems).)
   

   Connecting using HyperTerminal using COM1 (Serial).
4. Check the Flash: filesystem to verify it can fit the new IOS. {dir flash:}
   

   Checking size of Flash: using {dir flash:} command.
5. Use {copy xmodem: flash:FILENAME} command to copy the IOS from the computer. {copy xmodem: flash:c3750-ipservicesk9-mz.122-55.SE9.bin}
   

   Copying IOS using {copy xmodem: flash:*} command.
6. Click the transfer button and then send file while the previous command is still running to send the file (Use xmodem or xmodem-1K)
   

   Sending the exact file path using 1K Xmodem.
7. Once the install has finished verify the IOS has been installed to the Flash: filesystem. {Dir flash:}
8. Reset the switch and then verify the correct IOS is installed once more. {Reset}

Signature

Written 2/23/2021 by Nicholas A. Perez.