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We need replace to a pair of switches with new ones without interrupting traffic.

In order to do that , for some minutes all 4 switches will be interconnected between them - but we need to avoid stp recalculations - has anybody done that? any ideas how to design the migration without any stp recalculations ?

Some info:

We got 2 dc and we can work on backup while traffic flows to dc 1 and then we need to switch traffic to dc2 and work on dc1 with replacements - please see the basic design:topology

  • Sorry, but any changes will cause STP convergence. That will actually save your network from developing a loop and crashing the entire network. – Ron Maupin May 20 '18 at 6:57
  • Did any answer help you? If so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively, you can provide and accept your own answer. – Ron Maupin Dec 25 '18 at 8:33
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This is not possible with M/R/STP. RSTP, MSTP, or RPVST reconverge very quickly but not instantly.

Reconverge time is minimal when the root bridge doesn't change (which is probably the case in you scenario). When the root bridge changes it should only change once, set your priorities accordingly - connect the new root with default priority and once it's integrated, set the priority lower than the old root.

For an instant L2 replacement you'd need shortest path bridging, TRILL or similar (and probably some fiddling).

Another approach is to use routing over redundant links, these can be rerouted without delay.

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