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umer zubairi

Catalyst 4500X ROMMON Upgrade for IOS Release 3.6.6E



I'm upgrading the IOS of my 4500X switches to version 3.6.6E and planning to run the VSS.


Do I need to upgrade ROMMON or not? Didn't find clear information in below release notes:


My currently running ROMMON version is 15.0(1r)SG12.


I look forward to hearing from you. Thanking you all in advance.


Kind Regards,


Leo L
VIP Community Legend

Upgrade not required, however, for future-proofing I'd recommend upgrading the ROMmon sooner rather than later.

Thanks Leo, can you please check the below syntax for upgrading 4500X boxes:

Procedure (1)

  1. 4500-X# copy tftp bootflash:
    Address or name of remote host []?
    Source filename []? cat4500e-universalk9.SPA.03.06.06.E.152-2.E6
    Destination filename [cat4500e-universalk9.SPA.03.06.06.E.152-2.E6]?
  2. 4500-X(config)#boot system flash bootflash:cat4500e-universalk9.SPA.03.06.06.E.152-2.E6
  3. 4500-X(config)#no boot system flash bootflash:old-file name XXX
  4. 4500-X(config)#config-register 0x2102
  5. 4500-X#wr mem
  6. 4500-X#reload

Do I need to add the forward slashes '/' ? like the syntax below:


Procedure (2) 


1) copy tftp://<TFTP IP address>/<filename.bin> bootflash:

(2) boot system flash bootflash:/<filename.bin

(3) no boot system flash bootflash:/<old filename.bin


Kindly, let me know which one is correct. Procedure 1 or 2

Please also tell me that with config-register 0x2102 if the switch will boot from old IOS if new one fails to boot. 

Leo L
VIP Community Legend

Make sure your boot statement shows BOTH:
boot system bootflash:NEW_IOS.bin
boot system bootflash:OLD_IOS.bin

This way, if the new IOS is unable to be loaded, the switch will fall back to the old IOS.

But then which statement switch will read to boot? I thought this has to be done by the configuration register.

BTW Leo did you check forward slashes are needed in the syntax or upgrade procedure is exactly the same like 4500E. check the procedure(1) that I shared earlier and let me know if that is correct. I don't want the switches to go into ROMMON mode :(

Leo L
VIP Community Legend

The forward slashes would look like this: boot system flash bootflash:/filename.bin or boot system flash bootflash:filename.bin

During the bootup, if the config register is set to 0x2102, then the appliance will read the boot variable statement (found in the configuration) from top to bottom.