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I have some problems for understand RSTP. I read IEEE Std 802.1D™- 2004 and have some questions. In 17.3 I see this notes: Each Edge Port transitions directly to the Forwarding Port State, since there is no possibility of it participating in a loop.

But I don't see it in state machine schemes.

17.30 Port State Transition state machine doesn't have direct way for transit from Discarding state to Forwarding state with out Learning state.

and in 17.29.3 Designated Port states I don't see this behavior for Edge port. port with true operEdge first go to DESIGNATED_LEARN and then go to DESIGNATED_FORWARD.

Can you help me understand this moments?

TylerH
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janusak
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1 Answers1

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Please refer to Figure 17-22─Designated port role transtions in IEEE Std 802.1D™- 2004; 17.29.3 Designated Port states at page 176 as shown below.

In the case of an edge port (i.e,., operEdge == TRUE), when the link is up, the port state will transit from DESIGNATED_DISCARD to DESIGNATED_LEARN as the RED line and the condition 1. shown in below figure, and then it will move to DESIGNATED_FORWARD in the blink of an eye as the condition 2 and the BLUE line. It skips the fdWhile (forward delay) time.

Therefore, the note says that Each Edge Port transitions directly to the Forwarding Port State, since there is no possibility of it participating in a loop.

Figure 17-22─Designated port role transtions

Tomas
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