Upgrading bootloader on catalyst switches

[salemmahara]

Hello everyone

We all know Bootloader will be upgraded when you upgrade your IOS ( Not all time ).

Could you tell me how to upgrade or downgrade bootloader manually? ( Catalyst 2960S or X or any other catalyst series)

I think we should downgrade IOS and again upgrade it to change bootloader. Is it true and the only way?

[Leo Laohoo]

Bootloader is upgraded automatically during an IOS upgrade, for example from 12.2(55)SE (and earlier) to 12.2(58)SE (and later).

[salemmahara]

Hi Leo

Thanks for replying.

As you mentioned, Bootloader is upgraded automatically. But recently we found, sometimes Upgrading IOS (Which affects bootloader too), will cause some problems. So we have to use another version of IOS.

But every new IOS version is not equal to a new Bootloader version. And system failure wont be solve unless you change Bootloader too!

So if your Current IOS is 15x(y)z ( last version ) and you have problem, it means there is no other and new ios and bootloader version. Sooo imagine you upgrade to the newest version and it upgrades bootloader to a new version (Or last version) and there is a system failure. What is your solution to change IOS and bootloader TOGETHER? Downgrading to a specific IOS version? I'm pretty sure "changing both IOS and bootloader is the only way"

[Leo Laohoo]

Don't worry about what version of bootloader because it won't affect the operation of the appliance.

[salemmahara]

Thank you Leo

But imagine its necessary to change bootloader because we have a system failure. 

Bootloader affects IOS because it's its role.

[Leo Laohoo]

---

@salemmahara wrote:

But imagine its necessary to change bootloader because we have a system failure. 

---

I don't understand the obsession about upgrading the bootloader.  On a Catalyst 2K and 3K, it is not necessary because the IOS will upgrade/downgrade when necessary.  

[salemmahara]

OK, let me make it more clear.

Imagine you upgrade your switch and found that there are some instabilities. You then decide to downgrade. After downgrading your system comes up with Syst error. In this case some specialist say: It's caused by firmware incompatibility! So you'll try to downgrade to another version of IOS regarding to downgrade Bootloader too.

What's your idea?

[andresfr]

Hello  Salemmahara!

I hope you're doing well.

We all know Bootloader will be upgraded when you upgrade your IOS ( Not all time ). <--- This is correct, the bootloader is normally upgraded automatically when you perform a major software upgrade, or when you move from one software train to a different one. Not all software upgrades will cause the bootloader to also be upgraded, and depending on the platform, a software downgrade will not cause the bootloader to be downgraded: 

Ex. Catalyst 3850 - IOS-XE 16.3.x

" When you upgrade from any prior IOS 3.xE release to an IOS XE 16.x.x release for the first time, the boot loader may be automatically upgraded, based on the hardware version of the switch. If the boot loader is automatically upgraded, it will take effect on the next reload. If you go back to an IOS 3.xE release, your boot loader will not be downgraded. The updated boot loader supports all previous IOS 3.xE releases.

For subsequent IOS XE 16.x.x releases, if there is a new bootloader in that release, it may be automatically upgraded based on the hardware version of the switch when you boot up your switch with the new image for the first time"

My recommendation is that you always check the Cisco release notes corresponding to the software version and platform on which you're planning to perform the software upgrade to find information about bootloader upgrade.

Reference links:

Release Notes for Cisco Catalyst 3850 Series Switches, Cisco IOS XE Denali 16.3.x

https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst3850/software/release/16-3/release_notes/ol-16-3-3850.html#pgfId-1127089

Release Notes for the Catalyst 3750, 3560, 3560-C, 2960, 2960-S, 2960-C, and 2960-Plus Switches, Cisco IOS Release 15.0(2)SE and Later

https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst3750/software/release/15-0_2_se/release/notes/OL25301.html#pgfId-1042738

Also, not all the platforms allow to perform a manual bootloader/rommon upgrade. Catalyst 4500 Series will allow you to do this and rommon software is available at Cisco.com. However, this is not the case for platforms like Catalyst 2960-X, 3750, 3850 among others.

Upgrading the Supervisor Engine ROMMON from the Console - Catalyst 4500

https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst4500/release/note/OL_24829.html#pgfId-178803

I hope you find this information useful.

Regards,

[salemmahara]

Hi andresfr

Thanks for replying.

I'm actually looking for an exact and practical answer about this question:

If we upgrade our catalyst switch to the newest version and then try to downgrade to a version like 15.0(2)EX, does it make any change in bootloader (Downgrade) ?

Next, is it possible to upgrade or downgrade from an IOS to the other one and it makes any problem because of firmware incompatibility? I'm talking about series like 2960S , X , 3750, 3850 or any platforms which there is no separate firmware upgrading procedure designed for them. EX. downgrading from 15.2(2) to 15.2(1) or .... .

If yes, what would be the result? ( how switch shows this incompatibility?) . What is the solution in this case ?

[andresfr]

Hi salemmahara,

Could you please be more specific? What particular Cisco Catalyst platform/model are you talking about?

Regards,

[andresfr]

Sorry salemmahara,

I didn’t see you other post.

Again, this would depend on the platform. Some switches will upgrade the bootloader when performing a major upgrade, but then, if you decide to rollback to a previous software version the bootloader will remain the same since normally the new bootloader is compatible with the previous IOS/IOS-XE software version. This is the case of the Cisco Catalyst 3850 if you go from IOS-XE 3.xE to 16.x.x and then back to 3.xE:

“When you upgrade from any prior IOS 3.xE release to an IOS XE 16.x.x release for the first time, the boot loader may be automatically upgraded, based on the hardware version of the switch. If the boot loader is automatically upgraded, it will take effect on the next reload. If you go back to an IOS 3.xE release, your boot loader will not be downgraded. The updated boot loader supports all previous IOS 3.xE releases.”

I’m providing the previous example because is one that you can find publicly available at Cisco.com. For other platforms line 2960-X and 3750 and not finding the details but I’m assuming the behavior is similar considering that no manual bootloader upgrade is possible.

For Catalyst 3750, the only explicit mention to boot loader upgrade is related to FIPS:
https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst3750/software/release/15-0_2_se/configuration/guide/scg3750/swipaddr.html#19741


Also, normally those platforms that could have a compatibility issue between the bootloader and the IOS will allow to perform a manual rommon upgrade so you can guarantee compatibility. This is the case of Cisco Catalyst 4500 series, just to give an example. You can even find release specific Rommon Release Notes for a particular supervisor on this platform:

ROMMON Release Notes for WS-X45-SUP8-E, WS-X45-SUP8L-E, and WS-X45-SUP9-E
https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst4500/release/note/OL_30306-01.html
Regards,