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IOS Upgrade for 4500X & 4948E

umer zubairi


I've to upgrade the IOS of 4500X and 4948E switches but couldn't find the clear steps in Cisco's official documentations.

Versions selected to be used are:

(1) 4500X = 3.3.6E

(2) 4948E = 15.2.2E6

Please note that I'd like to upgrade without ISSU as it sometimes causes issues on the catalyst series.

**Kindly, also let me know if the ROMMON is also required to be upgraded on both the nodes.

Looking forward to hearing from you.

23 Replies 23

No worries Bro, as always it was a pleasure talking to you.


Hi Umer,

Did you complete your upgrade? If so, how did it go, and were you able to do it without interruption? Lastly, did you upgrade your ROMMON along with the IOS in one shot?

I'd like to go through the same process ... I'm at 3.4.0 and want to go to 3.9.2 Unfortunately ISSU is not an option so I need to do it manually, and I'd like to go about it without interrupting the network.



Hello Dan,

Not yet mate, but planning to do in the coming weeks I've around 12 boxes and all have to be VSS enabled.

Good that you decided to go with the manual upgrade. ISSU really sucks sometimes!!

IOS upgrade procedure is pretty simple, you just have to follow the below steps:

(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

(4) config-register 0x2102 (check the config register if it's already 0x2102)

(5) wr mem

(6) reload

Leo has shared the link above for the ROMMON upgrade I'm gonna follow the provided procedure. Here's the link:

To be honest I couldn't find a way to upgrade both in one shot and thinking to upgrade them one by one. 

Leo Laohoo
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There is no way to perform an IOS upgrade without interrupting a service.  There will be a downtime.  

The ROMmon upgrade alone will take around 20 minutes.

Hi Leo,

I am going to do software upgrade from 3.9.00 to 3.9.2.


My 4500x are running in vss.The default config-register is 0x2101 (i thought the default is always 0x2102).


Things not clear to me are



1: is there any difference between 0x2101 vs 0x2102? (should i change it to 0x2102 before boot? And changing it on active should be enough or do i have to do it on standby switch as well) 



2: show version is showing boot image as unknown.
System image file is "flash1:unknown"
ROM: 15.0(1r)SG12

However running config is showing.



3. should i follow the standard upgrade procedure
- copy image to flash of both switches
- Change boot system variable (should i keep the old version or remove it and if i want to keep it how to make sure new one is always preffered on both switches? Is there any command to set the order?

-boot the switch from cli of active switch (or is there boot command for stanby switch as well?).