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200-301.STP ConvergenceSTP brings every RP and DP into a forwarding state, while non-RP or DP ports become blocking. These states can remain for days, weeks, or months. However, there are times when some switch or link will fail, a particular link will change speed (changing STP overhead), or the STP configuration will change. Any of these factors can cause switches to duplicate their STP algorithms, which in turn can change their own RPs and any ports that act as DPs.When STP converges due to some change, not all ports must change their state. For example, for a port that is forwarding, if it still needs to forward, then it will remain in the forwarding state. A port that is being blocked and still needs to be blocked will also remain in the blocking state. But something happens when a port needs to change state, and the rules are as follows./speechboard. No change occurs for interfaces in the same STP state. 1 rinse . For an interface that needs to change from the forwarding state to the blocking state. the switch changes it to the blocking state immediately. For interfaces that need to change from the blocking state to the forwarding state, the switch first changes the interface to the listening state, followed by the learning state, each for the time specified by the forwarding delay timer (approximately 15 seconds). The interface is then placed in the forwarding state only. Since the transition from the blocking state to the forwarding state requires no additional steps, only some preparation is required for the concept of such a transition. The preparation can be done by reviewing Chapter 1 of this book.Troubleshooting Ethernet ChannelsThere are several reasons why you might encounter special challenges when troubleshooting an Ethernet channel. First, you must be careful to match the correct configuration, and there are more actual misconfigured combinations than correct ones. Second, many interface settings must match the physical link before the switch can add a physical link to the channel, including the local switch and the adjacent switch. The last part of this chapter covers both topics. incorrect options in the channel-group commandA small list of working configuration options for the channel-group command was listed in the "Configuring EtherChannels" section earlier in this book. For a single EtherChannel, these rules can be summarized as follows. F S(1) On the local switch, all physical interfaces must use the same channel-group number for the channel-group command. 1. calyx point (2) The channel-group numbers on adjacent switches may be different.(3) If you use theon keyword, it must be used on the corresponding interfaces on both switches.-4