Question

STP Loop Protect

  • 22 April 2021
  • 0 replies
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I was studying STP from the User guide , I came to this part of loop protect. My problem is that i don`t understand that part. i feel lost when i read this part.
Can anyone clarify that part for me and make it more simpler ?


“Loop Protect protects the network from loops. The Loop Protect feature is achieved by ports receiving
BPDUs (RSTP/MSTP only) on point-to-point ISLs before their states are allowed to become forwarding.
Further, if a BPDU timeout occurs on a port, its state becomes listening until a new BPDU is received. In
this way, both upstream and downstream facing ports are protected. When a root or alternate port
loses its path to the root bridge, due to message age expiration, it takes on the role of designated port
and will not forward traffic until a BPDU is received. When a port is intended to be the designated port
in an ISL, it constantly proposes and will not forward until a BPDU is received. It will revert to listening if
it stops getting a response. Loop Protect also overrides the port admin setting. This protects against
misconfiguration (such as disabling STP on a port) and protocol failure by the connected bridge.
Loop Protect has the capability to
• Control port forwarding state based on reception of agreement BPDUs
• Control port forwarding state based on reception of disputed BPDUs


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