We have 2x 10Gb aggregation switches at the core of our network and linking those 2 switches together is a pair of 25Gb QSFP DAC cables.
This evening we upgraded our 2x 10Gb aggregation switches to version 5.64.8.13083, which on a separate note i’m hoping will allow us to create more than the 6 aggregated links.
We upgraded the 2 switches one at a time but we noticed after a while the switches lost connection with each other.
Turns out that the 2x25Gb links don;t come up if the switches are on different FW levels, and because our Cloud key was connected through one of them via another switch, we lost connection to our entire stack.
In the end I had to put another cable in our network to join the 2 halves back together again to restore connectivity, then upgraded the FW on the other switch, and then our link came back up again.
Just wanted to give everyone a heads up on that in case they have a similar setup.
Moving forward I think i’m going to keep the 2x temporary 10Gb links in place, just in case i run into that issue again in the future, then at least I have multiple paths across our network, and just let spanning tree disable one of them. Just hoping it disables the slowest one though 