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lossless firmware upgrade on IRF(ed) TOR switches

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Trusted Contributor

lossless firmware upgrade on IRF(ed) TOR switches

Let´s imagine  racks with two TOR switches (A5120-EI, A5500-EI, A5500-HI, A5800, A5820) each, which are stacked using  IRF. Each server is connected to both switches, each of the TOR switches is connected via LACP to the core switch.

So, how to do a firmware upgrade on those top of rack switches with a minimum of service downtime? What about the following


First start with the normal upgrade steps:

  1. copy the boot-loader and the bootrom on each stack member
  2. commit the bootrom upgrade
  3. set the boot-loader file
  4. save
  5. But don´t "reboot" the whole switch now
  6. instead, remove the power cord on one of the switches
  7. put it in again, let the switch boot

It will hopefully get into the IRF stack without any problems? Without any connectivity interruption of the second switch? After that remove the power cord of the second switch and put it in again to upgrade that one.


Is this a good idea at all? It´s probably not HP´s best practice...I never tried that at all...

Honored Contributor

Re: lossless firmware upgrade on IRF(ed) TOR switches

not a good idea !


IRF is a complex protocol, which synchronizes a lot of control plane protocols in the stack.

This is why running multiple SW version in 1 stack is typically not supported (only for minor patch version differences).


The way to update is to use the ISSU process. (see manual).

This works for :

1/ compatible updates

minor firmware updates, which allow different versions to be online in the same stack

2/ incompatible updates

major updates, which does not allow different versions in the same stack (requires a "failover" when doing the update).


Sometimes neither of these 2 will be possible, so a manual update is required.

Attached some visio's I made in the past to explain the different steps for the different scenario's (and why using more than 2 units in the core/distribution/server edge is not recommended in my opinion, unless all connecting devices are connected to all IRF units).


The 2 ISSU docs explain the steps for the official ISSU process.

The manual procedure is just my own procedure in case you cannot use the official ISSU process,


Hope this helps,

Best regards,Peter