Question 372 - 220-1101 discussion

Port flapping, also known as link flapping, is a situation in which a physical interface on the switch continually goes up and down, causing intermittent connectivity for the devices connected to that port12. Port flapping can be caused by various factors, such as faulty or incompatible cables, hardware issues, configuration errors, or other network problems123.

The network logs show that interface 0/1 on the switch changes its status from up to down and vice versa several times within a short period of time. This indicates that the port is flapping and affecting the network connectivity. The log also shows that the switch was elected as the root bridge, which means that it is the central point of a spanning tree protocol (STP) network. STP is a protocol that prevents loops in a network by blocking some ports and creating a tree-like topology. Port flapping can cause STP to recalculate the topology and change the status of the ports, which can further disrupt the network performance2.

To troubleshoot port flapping, the technician should check the physical and hardware aspects of the device, such as cables, SFPs, gigabit interface converters, and power supplies. The technician should also check the configuration settings of the port, such as auto-negotiation, duplex mode, speed, power-saving features, and smartport. The technician should also check for other network issues that may cause port flapping, such as link synchronization and spanning tree issues123.