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spanning tree timer
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| "spanning tree timers are consistent throughout the bridge/switch topology and their value are set by the root bridge" (icnd from cisco press) page160
included the forward delay or just the hello time ?
frans | |
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| stp timers are set on the root bridge because non root bridges do not send configuration bpdu's. This includes hello timi, forward delay and max age.
Hello time default is 2 sec.
forward delay is default 15 sec and
max age default is 20 sec for a total of
50 seconds for spt convergence in case of failure.
I would be real weiry of changing it until you have an outstanding understanding of stp.
This can cause MAJOR PROBLEMS if you don't know what you are doing. Refer to the Cisco Press CCIE Lan Switching ch. 6 and 7 on spantree and advanced spantree and tuning.
I hope I answered your Q | |
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| thanks for your reply
it means that i just have to change these timers on the root bridge to modify the froward delay on all the non root bridges.
regarding the changes in network topology.
i understand why when the root bridge fails, an spt recalculation is initiated (no bpdu are sent> the nonroot bridges wait for the max age timer to expire>stp recalculation is initiated)(by the wait, who sends a signal for recalculation, and which kind of signal?)
but if the network topology is changed due to a failed nonroot bridge, what happen?
assuming that a nonroot bridge is not supposed to send bpdu, how the spt recalculation is it triggered?
thanks for your help
frans | |
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| the root sends config bpdu's and non root's send Topology change bpdu's back to root.
IF root fails, they go through max age and the next switch with lowest bid wins the election for root bridge and starts sending the config bpdu's. You can manually set the id's so that in case of failure, you guarantee the switch you want as backup is indeed the one that picks up the root.
Does that help? |
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