Network Consulting - Undocumented Cisco Commands. Cisco/Juniper Commands. Disabling Dynamic Trunking Protocol (DTP) Cisco's Dynamic Trunking Protocol can facilitate the automatic creation of trunks between two switches. When two connected ports are configured in dynamic mode, and at least one of the ports is configured as desirable, the two switches will negotiate the formation of a trunk across the link. DTP isn't to be confused with VLAN Trunking Protocol (VTP), although the VTP domain does come into play. DTP on the wire is pretty simple, essentially only advertising the VTP domain, the status of the interface, and it's DTP type. These packets are transmitted in the native (or access) VLAN every 60 seconds both natively and with ISL encapsulation (tagged as VLAN 1) when DTP is enabled.
DTP is enabled by default on all modern Cisco switches. First, it's simply bad design; trunks should be present where they were intended, and only where they were intended. ! However, even when a port is statically configured in such a manner, DTP is still active on the port. Switch(config-if)# switchport nonegotiate. Errdisable Port State Recovery on the Cisco IOS Platforms. Introduction This document defines the errdisabled state, describes how to recover from it, and provides examples of errdisable recovery. This document uses the terms errdisable and error disable interchangeably. Customers often contact Cisco Technical Support when they notice that one or more of their switch ports have become error disabled, which means that the ports have a status of errdisabled. These customers want to know why the error disablement happened and how they can restore the ports to normal.
Note: The port status of err-disabled displays in the output of the show interfaces interface_number status command. Prerequisites Requirements There are no specific requirements for this document. Components Used In order to create the examples in this document, you need two Cisco Catalyst 4500/6500 Series Switches (or the equivalent) in a lab environment with cleared configurations. The information in this document was created from the devices in a specific lab environment. Conventions.