10-18-2005 01:31 AM - edited 03-03-2019 12:28 AM
Hy,
one of my 3550 catalyst switch Port get always the message "LOOP_BACK_DETECTED: Keepalive packet loop-back d
etected on GigabitEthernet0/11". This Port goes then in the err-disable state. When I take the syntax "no errdisable detect cause loopback" then I get on an another switch the message "LOOP_BA..." too. What can I do?
10-18-2005 01:58 AM
Hi
In most cases its the faulty cable or the bad patching done which triggers this error log in the catalyst switch and also put the port in errordisable mode.
do revert what kinda equipment is getting connected on the other end of this switchport.
regds
10-19-2005 03:51 AM
Hi,
On Switches there is not much use of keepalives . Keepalives are just used as hellos between the 2 switches.They are not used to check the link reliability or error detection on the link as used in case of routers. You can safely remove the Keepalives from your switch interface and enabled UDLD inturn to check the uni-directional link problem.
UDLD is designed to work specially on GIG interfaces.
To remove the keeplaives:
conf t
int gig 0/11
no keepalive
To enable the UDLD:
http://www.cisco.com/univercd/cc/td/doc/product/lan/c3550/12225sec/3550scg/swudld.htm
HTH,
-amit singh
10-19-2005 07:30 AM
It has been my understanding that you typically use keepalives for copper ports and UDLD for fiber ports. Is this not correct?
10-19-2005 09:39 AM
that is right. It is not advisable to remove keepalives from the copper ports.Loopback detection through keepalives was a mechanism that was put in place to detect loops in the network
caused by Type1a or tyep2 copper cabling. While it is a good mechansim for those special
situations , there seems to be no need for having it enabled on the Gig ports where you
can use features like UDLD to detect a fiber loop or unidirectional fiber.
Salman Z.
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