Good day, folks.
In Petr Lapukhov document "understanding-stp-and-rstp-convergence" in section where considered convergense process in case of root bridge failure
(see pic.1 and notice that bridge X and bridge Y have best priorities in corresponded side and will be elected as temporary bridge, btw X has better BID than Y)
Pic. 1
there is a possible pace of developments:
If the bridge “A” hears about “X” before it hears about “Y”, it will invalidate
cached information about “R” and reach an agreement with “X” about new
root bridge. At the moment when inferior information from “Y” reaches “A”,
the latter will properly synchronize with “Y”, and a new root bridge will be
elected. The extra synchronization time required to wipe out old root
bridge “R” information is no longer required, as this information is never
propagated to “Y”.
I cant get why "A" should invalidate cached information about “R”, if it has ALTN port and didnt hear on it any iferior information from "Y"? In my understanding when “A” hears about “X” it should make re-root operation (cos it still thinks that "R" alive on it ALTN port) - change it ROOT port to previoulsy ALTN and start sync process downside to "X" bridge propagading that it have path to "R".
Only after inferior information from “Y” reaches “A”, it will try to propagate this information again downside to "X" bridge. "X" will reject this and start anounce himself as the root and propagation wave will bounce back to "Y". After this topology will become converged.
So the question - who is right here? I bet on Petr Lapukhov but want clarifications. I cant get why bridge can accept inferior information still having ALTN port to previous root bridge.
