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Community Member

VSS upgrade from 12.2(33)SXH3a to 12.2(33)SXH6 - instructions?


My goal is to upgrade our 6509 VSS from 12.2(33)SXH3a to 12.2(33)SXH6 to mitigate a few bugs.

The best information i have found that documents the procedure is a white paper

The upgrade instructions that i believe i am to follow are pages 57-62 BUT these instruction only talk about the installing of the modular IOS not booting from the image.

My plan is

copy the new image to sup-bootdisk:

copy the new image to slavesup-bootdisk:

enter command boot system flash sup-bootdisk:s72033-ipservicesk9_wan-vz.122-33.SXH6.bin (command currently in config boot system flash sup-bootdisk:)

enter command wr

enter command redundancy reload shelf 2

wait for reload and check things out

enter command redundancy force-switchover

Does anyone have any issue with the above procedure, i can find any documentation that fits my scenario exactly.

Does anyone have any experience of upgrading VSS?

Can anyone point me in the direction of documentation?

Any pointers or tips appreciated.



VIP Super Bronze

Re: VSS upgrade from 12.2(33)SXH3a to 12.2(33)SXH6 - instruction

Hi Chris,

There are 2 ways to upgrade a VSS pair.

1-You copy the latest image (SXI3) into your sup-bootdisk and slavesup-bootdisk and delete the old boot variable command and add the new one and save config and reboot both boxes at the same time. This is very similar to what you already describe in your post.  If you do it this way there is a downtime of about 20 minutes until all the line cards came up and do the diagnostic and etc..... If you have an outage window, I would suggest doing it this way.  You reboot the set once and done.

2-If you do not want to have down time at all then you can use ISSU/eFSU to upgrade one device at the time with no downtime.  The way ISSU works is you upgrade the back up box first and then reboot it.  After the back up box comes up you force it to take over as the primary and then upgrade the old primary and reboot.

The entire process takes about 2 hours (because of multiple reboots).  If you decide to use ISSU, follow the instructions in this link carefully to make sure your upgrade is sucessfull

Good Luck


Community Member

Re: VSS upgrade from 12.2(33)SXH3a to 12.2(33)SXH6 - instruction


Thank you for your reply,

I dont believe the current IOS 12.2(33)SXH3a has the ability to perform ISSU/eFSU, i looked into this but i dont have the commands available.

The way i have documented in my post is described as FSU in the white paper, the down time is stated as 2 minutes whilst the backup switch transitions from RPR to SSO.

I'm interested in you thoughts between the reload (both at same time) to bring in the new IOS and the FSU reload (separate reloads but not the eFSU) process. You stated the reload was prefered, i need to minimise downtime but need to minimise risk also.

Thanks again for you reply


PS do you know where i can find what the difference between SXH and SXI

VIP Super Bronze

Re: VSS upgrade from 12.2(33)SXH3a to 12.2(33)SXH6 - instruction

Hi Chris,

Use the feature navigator to do a side by side comparison for different IOS images.

If your current IOS does not support it, I would defiantly use option number 1 I described.

Even though I like eFSU and we tested it in our lab and it really works well, if I have an outage window, I would prefer to reboot the boxes one time and be done with it.



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