Loopback Detected Error
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SwitchingSpanning Tree ProtocolTroubleshoot and AlertsConfiguration Example and TechNotes Errdisable Port State Recovery on the Cisco IOS Platforms Download Print Available Languages Download pm-4-err_disable link-flap error detected Options PDF (143.8 KB) View with Adobe Reader on a variety of pm 4 err_disable bpduguard error detected devices ePub (82.1 KB) View in various apps on iPhone, iPad, Android, Sony Reader, or Windows Phone Mobi
%ethcntr-3-loop_back_detected: Loop-back Detected
(Kindle) (87.6 KB) View on Kindle device or Kindle app on multiple devices Updated:Mar 23, 2016 Document ID:69980 ContentsIntroductionPrerequisitesRequirementsComponents UsedBackground InformationPlatforms That Use ErrdisableErrdisableFunction of ErrdisableCauses of ErrdisableDetermine If Ports
Pm-4-err_disable Channel-misconfig (stp) Error Detected
Are in the Errdisabled StateDetermine the Reason for the Errdisabled State (Console Messages, Syslog, and the show errdisable recovery Command)Recover a Port from Errdisabled StateCorrect the Root ProblemReenable the Errdisabled PortsVerifyTroubleshootRelated Information 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 %ethcntr-3-half_dux_collision_exceed_threshold 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 switches should run Cisco IOSĀ® Software and each switch should have two Fast Ethernet ports that are capable of EtherChannel and PortFast. The information in this document was created from the devices in a specific lab environment. All of the devices used in this document started with a cleared (default) configuration. If your network is live, make sure that you understand the potential impact of any command. Backgr
to find this is in the output of show interfaces status. A switch port can end be error
Pm-4-err_disable Psecure-violation Error Detected
disabled if the software (IOS or CatOS) detects an error cscea46385 situation on the port. The port is effectively shut down until re-enabled manually or automatically if a disable keepalives in cisco switch recovery timer is specified for the error condition. One such error condition results from the existence of a loopback on the port. The switch sends keepalive packets http://www.cisco.com/c/en/us/support/docs/lan-switching/spanning-tree-protocol/69980-errdisable-recovery.html out all interfaces. If a keepalive packet is received on the same interface it was sent from, then a loop exists that has not been blocked by Spanning-Tree Protocol. If this occurs, these messages are generated (these specific messages are from a Cisco Catalyst 2940). %ETHCNTR-3-LOOP_BACK_DETECTED: Keepalive packet loop-back detected on FastEthernet0/3.
%PM-4-ERR_DISABLE: loopback https://slaptijack.com/networking/err-disabled-loopback-edition/ error detected on Fa0/3, putting Fa0/3 in err-disable state
To resolve the problem, you must investigate the network beyond the port that is complaining and discover what sort of logical loop might exist that was undetectable by STP. Often, less capable devices (inexpensive unmanaged switches or hubs) are the culprit. Related Reading: Cisco Field Manual: Catalyst Switch Configuration by David Hucaby, Stephen McQuerry Building Cisco Multilayer Switched Networks by Richard Froom, Balaji Sivasubramanian, Erum Frahim Related Posts UDLD In Radio-Based Metro Ethernet Rings Cisco Catalyst 3560 POST Output Allowing DHCP Option 82 in Cisco DHCP Relay Agents Brand New ME3400G Can't Ping! 3 Reasons You Should Be Using Rapid Spanning Tree (802.1w) Get Slaptijack updates delivered to your Inbox or RSS Reader for free! CATEGORIES Graphics Design Information Systems IT Management Networking Programming Software System Administration Uncategorized Voice / Voice over IP ARCHIVES 2016 2015 2014 2013 2012 2011 2010 2009 2008 2007 © 2016 Slaptijack All Rights Reserved · Wordpress
2008 Loopback detected, port went error-disabled suddenly Email ThisBlogThis!Share to TwitterShare to FacebookShare to Pinterest One working switch port on my Cisco http://showipprotocols.blogspot.com/2008/01/loopback-detected-port-went-error.html Catalyst 2950 suddenly went down by itself! Of course, my phone rang when I was having dinner, and then I had to tell my colleagues how to do a port http://www.networking-forum.com/viewtopic.php?f=33&p=243513 reset step by step. Luckily, after the port reset, the port went back on. I did not pay much attention to this event, until it happened to the same port again! error detected This time, I drilled in to check the log, and found something suspicious: .Jan 30 10:12:25: %ETHCNTR-3-HALF_DUX_COLLISION_EXCEED_THRESHOLD: Half-duplex loopback detected, collision threshold exceeded on FastEthernet0/24. .Jan 30 10:12:25: %PM-4-ERR_DISABLE: loopback error detected on Fa0/24, putting Fa0/24 in err-disable state .Jan 30 10:12:26: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/24, changed state to down .Jan 30 10:12:27: %LINK-3-UPDOWN: Interface FastEthernet0/24, changed state to loopback detected error down After my survey on Cisco.com, I found a workaround to this: just disable keepalive on that interface: Switch # config t Switch (config)# int f0/24 Switch (config-if)# no keepalive I believe that it is a software caveat. The phrase mentioned on the web page is: ..... The suggested workaround is to disable keepalives and upgrade to Cisco IOS Software Release 12.2SE or later. ..... References: Errdisable Port State Recovery on the Cisco IOS Platforms Do you like this post? You really should consider Subscribing by Email! Email ThisBlogThis!Share to TwitterShare to FacebookShare to Pinterest Tweet Posted by Li-Ji Hong at 5:24 PM Reactions: Location: Wanhua District, Taipei City, Taiwan No comments: Post a Comment Tip: you can also anonymously comment here. Newer Post Older Post Home Subscribe to: Post Comments (Atom) Popular Posts BGP sample practice, in the new Packet Tracer 5.3 I created this practice to test the Packet Tracer 5.3 features of BGP. Dual Stack IPv6 and IPv4 configuration (CNA-04-006) CCNA Exploration 4.0, Semester 4, "Dual Stack IPv6 and IPv4 configuration " Packet Tracer 5.0 practice file (C
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