Posted on October 6, 2021 3:19 pm
 |  Asked by David Kim
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I have two old switches (DCS-7050S) in MLAG pair that needs to be replaced soon.

I’m wondering if I can take out one of the MLAG pair and replace it with a newer model switch (DCS-7050SX3)

Then take out another old MLAG pair and replace with a newer model. Basically take the old switch out put new in, one by one.

If this isn’t possible, I’ll need to come up with another plan to minimize the impact.

Posted by John Gill
Answered on October 6, 2021 9:15 pm

It is possible, assuming you are running the same code.  We support different code during MLAG ISSU (upgrades) for a short period of time, but you're already changing hardware and the fewer variables you can introduce, the better.  You should approach running MLAG between different platforms similarly.  It doesn't stop you from forming, but we do not have a test matrix where N to N platform combinations are tested.  You can connect it, let MLAG form, and wait for the MLAG port-channels to come up and pass traffic.  Be vigilant at this point, and config changes affecting the forwarding path or control plane should be avoided.  Just focus on the reboot and replacement of the remaining switch, ideally immediately.

Posted by Aniket Bhowmick
Answered on October 7, 2021 3:11 am

Hi David

You can bring up the MLAG between the 7050S and 7050SX3 model as long as the software supports it, but it can have inconsistencies or abnormal behaviours. Brining MLAG between two different Hardware Model is not officially recommended.

If you plan on doing this in a production setup then we would recommend to not use MLAG between the different models as it may lead to some impact.



Posted by David Kim
Answered on October 8, 2021 7:33 pm

I've tested two different versions in MLAG pair in GNS3 and did notice the inconsistencies but wanted to confirm what'd be like with two different model switches. The goal here is to make sure the traffic pass while replacing the old switches with the new ones and minimize the impact as much as possible. I'll make sure to match the code on all 4 switches (2 old, 2 new). Thank you both for your responses.

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