The plug-and-play Spanning Tree protocol (STp), a layer 2 protocol that ensures a loop-free topology in bridged laNs, has been around for decades.
Loop protection Loop protection mechanism is used to prevent accidental loops that can occur when an unmanaged non-spanning-tree-capable equipment is connected and drops spanning-tree packets. When loop protection is enabled on a port, it sends out a loop protocol packet; if it then receives the same ...
Spanning-Tree Protocol Enhancements with Loop Guard and BPDU Skew Detection Features Contents Introduction Prerequisites Requirements Components Used
A failure in the STA generally leads to a bridging loop (not a spanning tree loop, as you do not need STP to have a loop). Most customers that call Cisco Technical Support for spanning tree problems suspect a bug, but
The following diagram depicts switch behavior with STP enabled. With spanning tree, traffic cannot loop because only one path is in forwarding state.
CHAPTER 9-1 Catalyst 6500 Series Switch Software Configuration Guide—Release 8.7 OL-8978-04 9 Configuring Spanning-Tree PortFast, UplinkFast, BackboneFast, and Loop Guard
Spanning-Tree Protocol Enhancements with Loop Guard and BPDU Skew Detection Features Document ID: 10596 Introduction Prerequisites Requirements Components Used Conventions Feature Availability Brief Summary of STP Port Roles STP Loop Guard Feature Description Configuration ...
But practically, if all users in a certain bridging domain have connectivity issue at the same time, you can already suspect a bridging loop. Check the port utilization on your devices and look for abnormal values.
The worst case scenario is when a bridge sending BPDUs is configured for half-duplex on a link whereas its peer is configured full duplex. In the above example, the duplex mismatch on the link between bridge A and B can easily lead to a bridging loop.
Understanding Loop Protection for STP, RSTP, VSTP, and MSTP on EX-series Switches EX-series switches provide Layer 2 loop prevention through Spanning Tree Protocol