Spanning tree loop guard

  • US 7,061,875 B1
  • Filed: 12/07/2001
  • Issued: 06/13/2006
  • Est. Priority Date: 12/07/2001
  • Status: Active Grant
First Claim
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1. In an intermediate network device having a plurality of ports for forwarding network messages within a bridged network, a method for preventing the formation of loops within the bridged network, the method comprising the steps of:

  • executing a spanning tree protocol (STP) at the intermediate network device so as to elect a root of the bridged network and to transition at least one of the device'"'"'s ports among a plurality of spanning tree port states, including a discarding state, a listening state and a forwarding state;

    periodically receiving configuration bridge protocol data unit (BPDU) messages at one or more of the device'"'"'s ports;

    in response to the periodic receipt of BPDU messages being stopped on a given port, (1) preventing the given port from transitioning to the forwarding spanning tree port state, if the given port is in a spanning tree port state other than the forwarding spanning tree port state, or (2) precluding the given port from forwarding or receiving network messages, if the given port is in the forwarding spanning tree port state.

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