Verify the Configuration of RSTP
The 802.1d and PVST+ spanning-tree protocols have convergence times between 30 and
50 seconds. The RSTP and PVRST+ spanning-tree protocols have convergence times
within one or two seconds. A slow convergence time may indicate that not all of the
switches in your network have been con?¬?gured with RSTP, which can slow the convergence
times globally in your network. Use the show spanning-tree command to verify the
spanning tree mode.
Summary of Troubleshooting Switched Networks
The list that follows summarizes the key points that were discussed in this section.
?– Effective switched-network troubleshooting begins by understanding what makes a
network function correctly.
?– Hardware issues and port con?¬?guration errors can cause port connectivity issues.
?– Native VLAN mismatches and trunk mode mismatches can prevent a trunk link from
being established.
88 Chapter 2: Medium-Sized Switched Network Construction
?– Understanding how VTP works is the best defense when troubleshooting VTP
problems.
?– One of the primary objectives when dealing with an STP failure is to break the loop
and restore connectivity as soon as possible.
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