I found the same question has been asked before (https://forum.opnsense.org/index.php?topic=4288.msg1594) - but no answers at that time:
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Quote from: toysareforboysit would be a lot easier to see big traffic spikes if the traffic graph didn't auto scale. I would like to lock it at 50/10 so the minor traffic doesn't show up as big spikes and attract my attention unnecessarily.
Personally I would prefer to be able lock the scale to the max throughput possible for the interfaces, and 100% for the CPU (as it was in the previous interface). And I think that it should be possible on dashboard, and on all other performance graphs.
I find that the current display is more for showoff than actually useful. I wonder if the new Dashboard interface will have the possibility in the future, or if I can add this feature to wish list?
+1 from me.
Until I get a more infra-wide dashboard in place I have same report up on a spare monitor and would love to ignore spikes from re-scaling the Y axis.
At least CPU should definitely be fixed to 100% IMHO. It's not relevant if it's 4% or 6% - the fact that the line is "really low" is good enough and should be quickly discernible.