I have a relatively large layer 2 network where port flapping is not uncommon. I am using Juniper EX 2200 switches, which clear out the mac-forwarding table on a topology change. It is not uncommon for ports to flap in our network, devices reboot, etc.. Each time a port flaps, a TC is sent throughout the network and all of my EX switches flush out the ethernet-switching tables. This creates a pretty large flood while the switches re-learn. Has anyone experienced an issue similar to this? Do you have any suggestions to limit the flooding that happens after an STP TC? Is there anything that I can configure on the EX switches to limit the flood?


  • @Robert answer should be enough. Moreover, remember that a Topology change not always implies a recalculation of spanning tree.
    – KorXo
    Mar 20, 2015 at 9:26
  • 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 could provide and accept your own answer.
    – Ron Maupin
    Aug 11, 2017 at 14:41

1 Answer 1


TCNs are only generated from non-edge ports when they receive a BPDU. Verify that your access ports are configured as edge ports under your spanning-tree config.

set protocols rstp interface ge-0/0/0 edge

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