When Spanning Tree is converging no data is being sent?

No data will be forwarded until convergence is complete. says on page 521 of CCNA Study Guide 7th edition.

Is this between host on different switches connected by a cable? Or is this between host on the same switch?

For example, I have a Switch A and Switch B which are connected together by a crossover cable. I have 2 hosts connected to switch A. Suddenly there was another switch or cable connected between switch A and B causing STP to try to converge. Does this mean that the two host on Switch A won't be able to talk to each other while the STP is trying to converge?

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Coolhandluke

vazurahan wrote: »

For example, I have a Switch A and Switch B which are connected together by a crossover cable. I have 2 hosts connected to switch A. Suddenly there was another switch or cable connected between switch A and B causing STP to try to converge. Does this mean that the two host on Switch A won't be able to talk to each other while the STP is trying to converge?

No. Hosts connected to the same switch will be fine. data will still flow between them. Only ports that potentially create a loop will try to converge.

STP has various stages that it must go through to ensure no loops exist in the network. In your example when you connect the second cable between the switches, the switches will both start the new connection ports in the "Blocking" state. When they receive a BPDU from each other they will compare the original connection BPDU with the new BPDU for the new connection. If the original is superior, the connection will be maintained and the second connection will remain in a "Blocked" state (on one side of the second connection). If the second connection has a superior BPDU then the port must progress through the STP port states (Listening, Learning, Forwarding). The original connection will be moved into a "Blocking" state on one side of the connection to prevents loops. This all seems like a slow process (at least 30 seconds) but there are many methods to accelerate the process.

I realise that it may be a long answer to a short question as you may not have got that far into your reading yet but the process can get confusing.

hope this helps, If not keep reading it will start to make more sense.

luisYme

agree with coolhandluke (awesome movie!)... but just to add, if the two hosts on switch A are in different VLANs then there is a chance they could be negatively impacted by the STP convergence if switch A isn't performing any layer 3 functions. i'm not sure if that's the case in your example, but just something to keep in mind.

good luck!

vazurahan

Thank you very much. Finally understand it now.