https://www.cisco.com/c/en/us/td/docs/switches/lan/cisco_ie3000/software/release/12-2_52_se/configuration/guide/ie3000scg/swudld.html
Cisco IE 3000 Software Configuration Guide, Release 12.2(52)SE - Configuring UDLD [Cisco Industrial...
https://www.cisco.com/c/en/us/td/docs/switches/connectedgrid/cgs2520/software/release/12_2_53_ex/configuration/guide/scg2520/swudld.html
CGS 2520 Switch Software Configuration Guide, 12.2(53)EX - Configuring UDLD [Cisco 2500 Series...
This chapter describes how to configure the UniDirectional Link Detection (UDLD) protocol on the Cisco CGS 2520 switch.
https://www.cisco.com/c/en/us/support/docs/lan-switching/spanning-tree-protocol-stp-8021d/218321-configure-stp-with-loop-guard-and-bpdu-s.html
Understand STP Loop Guard and UDLD Features - Cisco
This document describes Spanning Tree Protocol features that are intended to improve the Layer 2 network stability.
understandstploopguardfeatures