logging event trunk
http://www.cisco.com/c/en/us/td/docs/ios/fundamentals/command/reference/cf_book/cf_l1.html
To enable trunk status messaging, use the logging event trunk-status command in interface configuration mode. To disable trunk status messaging, use the no form of this command.
udld port aggressive
http://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst6500/ios/12-2SX/configuration/guide/book/udld.html
Normal-mode UDLD classifies a link as unidirectional if the received UDLD packets do not contain information that is correct for the neighbor device. In addition to the functionality of normal mode UDLD, aggressive-mode UDLD puts ports into the errdisabled state if the relationship between two previously synchronized neighbors cannot be reestablished.
spanning-tree guard loop
http://www.cisco.com/c/en/us/support/docs/lan-switching/spanning-tree-protocol/10596-84.html
The STP loop guard feature provides additional protection against Layer 2 forwarding loops (STP loops). An STP loop is created when an STP blocking port in a redundant topology erroneously transitions to the forwarding state. This usually happens because one of the ports of a physically redundant topology (not necessarily the STP blocking port) no longer receives STP BPDUs. In its operation, STP relies on continuous reception or transmission of BPDUs based on the port role. The designated port transmits BPDUs, and the non-designated port receives BPDUs.
When one of the ports in a physically redundant topology no longer receives BPDUs, the STP conceives that the topology is loop free. Eventually, the blocking port from the alternate or backup port becomes designated and moves to a forwarding state. This situation creates a loop.
The loop guard feature makes additional checks. If BPDUs are not received on a non-designated port, and loop guard is enabled, that port is moved into the STP loop-inconsistent blocking state, instead of the listening / learning / forwarding state. Without the loop guard feature, the port assumes the designated port role. The port moves to the STP forwarding state and creates a loop.
load-interval 20
http://www.cisco.com/c/en/us/td/docs/ios/fundamentals/command/reference/cf_book/cf_l1.html
To change the length of time for which data is used to compute load statistics
