Cisco Support Community
Showing results for 
Search instead for 
Did you mean: 

Licence upgrade for 4500X VSS

My user distribution layer consists of a pair of 4500X-32 running XE 3.4.2.SG configured as VSS.  I want to upgrade the license from IP base to enterprise (because I need vrf-lite), and I want the upgrade to be seamless.  I also want to do it online, not through the console port.  I have searched around for documentation, and none of it seems very clear.  Mostly it deals with dual-supervisor ISSU, which is a different scenario.  I am aware of the white paper on Software Activation Licensing Deployment, and of the section at the end of Chapter 5 of the Software Configuration Guide, but they are not very reassuring.

This is the procedure I am proposing.  Is there someone out there with real experience of this scenario who can tell me if this will work?

Starting off with chassis #1 as the active control plane, and chassis #2 as the standby:

  1. Copy .lic file for chassis #1 from tftp to bootflash:
  2. license install bootflash:<xxx.lic>
  3. redundancy force-switchover (to chassis #2)
  4. Do I need to log back in, or will my telnet switch over statefully?
  5. redundancy reload peer (this should reload chassis #1 only)
  6. Copy -lic file for chassis #2 from tftp to bootflash:
  7. license install bootflash:<xxx.lic>
  8. redundancy force-switchover (back to chassis #1)
  9. Do I need to log back in, or will my telnet switch over statefully?
  10. redundancy reload peer

So ... will this work, and will it be seamless?

Thanks in advance for any comments.

Kevin Dorrell



Hall of Fame Super Gold

My opinion:  You'll need to

My opinion:  You'll need to break VSS, copy and update the license files to each unit, upgrade the feature set individually and then resume the VSS.

So can that be done

So can that be done seamlessly, with no interruption to the user service?  At what point would you reload each chassis, and how would you ensure that the other one is ready to take over the traffic?



Hall of Fame Super Gold

Hi Kevin, No, not possible.

Hi Kevin, 

No, not possible.  When you break VSS, you break "things".  

VIP Super Bronze

Kevin,The answer to questions


The answer to questions 4 and 9 is, yes you will lose connection and so you have to log back in to the active sup.

I have never done this but I am afraid you will break VSS if you do it the way you described it above.

And the reason I think it will break VSS is because as soon as you apply step-3 you will have 2 switches with different license levels and VSS may not like that.

One thing you don't want do is not to be sure exactly how VSS behaves in this situation and not have access to console in case something goes wrong.


Thank you Reza and Leo for

Thank you Reza and Leo for your contributions.

It is a pity ... I was rather hoping that VSS would give me some workable procedure to do an ISSU.  My distribution switch is almost entirely VSS except for one port on each chassis that is a loop to a remote site, controlled by RSTP.  I have tested the VSS by brutally switching off one chassis or the other, and the VSS seems to work perfectly with no user interruption, and only about 3 seconds convergence on the RSTP ports.

It is a pity if you cannot leverage that resilience to perform a seamless software/licence upgrade.  All the published ISSU procedures are based on 4500 chassis and dual supervisors.   There does not seem to have been any effort to develop an ISSU procedure for the VSS topology.  Indeed, there does not seem to be any consensus of opinion exactly how VSS will behave in this situation (as Reza observes in his last paragraph). Even the Software Configuration Guide, page 5-83, seems uncertain how it will behave: "Shutting down the VSL ports on the VSS active detaches the standby, which might transition to the VSS active.)

That is really why I asked the question in the first place: I was wondering whether anyone here had any direct experience of this.

Thanks for your contributions anyway guys.  I shall book a maintenance slot and see if I can find an ISSU procedure that works for VSS.  I shall post back if I feel it would be useful.

Kevin Dorrell


Hall of Fame Super Gold

OMFG, please DO NOT use ISSU.

OMFG, please DO NOT use ISSU.   You are asking for trouble.  


I've tried iSSU on a Sup7E, let me tell you, it's painful.  I had to do the upgrade the old-fashion way:  Copy the IOS, change the boot statement and then reload the chassis.  

CreatePlease to create content