3.4.6 - Network Loop and Broadcast Storm Issues

CompTIA 3.4.6

A network loop

• Is where flooded frames circulate the network perpetually

Broadcast storm

• Will cause network utilization to go to near maximum capacity and the CPU utilization of the switches to jump to 80% or more

• Makes the switched segment effectively unusable until the broadcast storm stops

If there is a loop

• Spanning Tree Protocol should shut down the port

What should you do after isolating the problem to a segment of the network?

• Inspect physical ports that correspond to the disabled interfaces for looped connections

• At the patch panel, this could mean a patch cable that connects two ports on the same switch.

• On the office floor, it could mean a patch cable between two wall ports

If a broadcast storm occurs on a network where spanning tree is already enabled, you should investigate the following potential causes:

• Verify compatible versions of Spanning Tree Protocol or Rapid Spanning Tree Protocol are enabled on all switches.

• Verify the physical configuration of segments that use legacy equipment, such as Ethernet hubs.

• Investigate networking devices in the user environment and verify that they are not connected as part of a loop. Typical sources of problems include unmanaged desktop switches and VoIP handsets.