Kinglsey, The configuration of both is valid. UDLD will detect miswiring issues whereas LoopGuard will detect STP failures in software.
Here is a link to the comparison: http://www.cisco.com/en/US/tech/tk389/tk621/technologies_tech_note09186a0080094640.shtml#loop_guard_vs_uld Also take a look at this excerpt from http://www.cisco.com/en/US/prod/collateral/switches/ps5718/ps708/prod_white_paper0900aecd805457cc.html While UDLD can be used to detect "directionality" problems on any Ethernet link, another feature should be used in synergy with UDLD to guarantee greater STP robustness: the feature in question is called STP Loopguard. The main advantage of Loopguard is that it is part of the STP algorithm and so it proactively acts and reacts to STP events at the same speed of the STP protocol. Its main disadvantage is that it runs on logical links, as STP does, whereas other features like UDLD and PAgP/LACP run on the individual physical links and so have a lower level type of visibility into connectivity problems. As a generic principle, feature combinations can offer a better protection than the individual features alone, and it is therefore recommended to fully exploit feature synergies when possible. Regards, Brandon Carroll - CCIE #23837 Senior Technical Instructor - IPexpert Mailto: [email protected] Telephone: +1.810.326.1444 Live Assistance, Please visit: www.ipexpert.com/chat eFax: +1.810.454.0130 IPexpert is a premier provider of Classroom and Self-Study Cisco CCNA (R&S, Voice & Security), CCNP, CCVP, CCSP and CCIE (R&S, Voice, Security & Service Provider) Certification Training with locations throughout the United States, Europe and Australia. Be sure to check out our online communities at www.ipexpert.com/communities and our public website at www.ipexpert.com. On Thu, Jan 7, 2010 at 9:13 AM, Kingsley Charles <[email protected]> wrote: > Hi all > > In switch, we have two features loop guard and UDLD that can detect an > uni-directional port/link. > > UDLD transmits UDLD packets to check for link bi-directional status and > shutdowns (errdisable) the port when it finds unidirectional > Loop guard checks for BPDUs and puts the port in loop-inconsistent state > when the port is unidirectional which automatically recovers when BPDU is > recieved. > > > Now, the switch allows to configure both the features on a port. > > > If a port becomes uni-directional both the features will be triggered. Which > feature will take precedence and take the action. Will the port be shutdown > or in loop inconsistent state. > > Is it valid configuring both the feature on a port? > > > > > > With regards > Kings > _______________________________________________ > For more information regarding industry leading CCIE Lab training, please > visit www.ipexpert.com > > _______________________________________________ For more information regarding industry leading CCIE Lab training, please visit www.ipexpert.com
