%PM-4-ERR_DISABLE: loopback error detected on Gi0/2

[Tompeshwar Lal]

Dear Sir,

I have config. new cisco 2960 se Swtich on our LAN that is connected with another cisco switch with trunk with crass cable.

backbone link is down frequtly since i have installed it on network follwing Eror has shown in log

May 20 15:03:17.223 India: %ETHCNTR-3-LOOP_BACK_DETECTED: Loop-back detected on
GigabitEthernet0/2.
May 20 15:03:17.223 India: %PM-4-ERR_DISABLE: loopback error detected on Gi0/2,
putting Gi0/2 in err-disable state
May 20 15:03:18.229 India: %LINEPROTO-5-UPDOWN: Line protocol on Interface Gigab
itEthernet0/2, changed state to down

Can any body tell me whts prob.

...............................................................................................

and one more prob..

follwing cmd is automatically configured on new switch

!
crypto pki trustpoint TP-self-signed-1076337536
enrollment selfsigned
subject-name cn=IOS-Self-Signed-Certificate-1076337536
revocation-check none
rsakeypair TP-self-signed-1076337536
!
!
crypto pki certificate chain TP-self-signed-1076337536
certificate self-signed 01
  3082023F 308201A8 A0030201 02020101 300D0609 2A864886 F70D0101 04050030
  31312F30 2D060355 04031326 494F532D 53656C66 2D536967 6E65642D 43657274
  69666963 6174652D 31303736 33333735 3336301E 170D3933 30333031 30303030
  35305A17 0D323030 31303130 30303030 305A3031 312F302D 06035504 03132649
  4F532D53 656C662D 5369676E 65642D43 65727469 66696361 74652D31 30373633
  33373533 3630819F 300D0609 2A864886 F70D0101 01050003 818D0030 81890281
  8100AEE1 20B64C5B 4F831F44 AE90A8B7 5C60D1B1 4662B4B3 36865A3E 43F974F1
  9DA7521E 692A4F13 4F447483 868A0448 322006CA AA404B31 5ED05776 76BCC3A0
  0C15BF47 2176F5AC EAFB06E4 D8F49BB1 0A999AAE F3922648 63447BEC D31E1359
  4F8565C6 1CF5A066 7F9D43F3 F8E5FA3B 380AF1CB F5E630D5 53A921E2 E62A3560
  176B0203 010001A3 67306530 0F060355 1D130101 FF040530 030101FF 30120603
  551D1104 0B300982 07535732 5F47462E 301F0603 551D2304 18301680 145041F9
  C03F664F A1090118 0837DC12 90761ED4 F6301D06 03551D0E 04160414 5041F9C0
  3F664FA1 09011808 37DC1290 761ED4F6 300D0609 2A864886 F70D0101 04050003
  81810018 76970781 17981390 979FBA1E 9CA904AF 5050BAF1 5F2EE233 FACF7C69
  F57CE8F2 B1EF224F 126A3EB9 5A797456 00C11FA8 86E43C25 D74C0EB2 AF8A5EE7
  D45F14E7 C75FCA25 14250CFB A28507A1 66617E60 761A4F68 F1E9DD15 29B3D6FE
  32AC4BBE 887687CE 890D67F5 2BE050F8 CAAC237A 50177347 DB3E2C16 65FD0AEE 66490A
  quit
!

wht is this?????????????? and how do i remove it......

Thanks in adv...

Tom

[spremkumar]

Hi

Do check for the faulty cable, once you connect with a new cable then enable the ports on both the switches.

I think those config lines are related to SSH access onto your switch.

regds

[Tompeshwar Lal]

i have alredy changed 2-3 times

but still..prob is same.....

[spremkumar]

Hi

Can you post the output of show run pertaining to the particular switchport from both the switches and also the output of show version both the switches here?

regds

[narendrakumar1987in · Accepted solution]

Hi Tom

       Following is taken from a Cisco document and you might find this useful.

     A loopback error occurs when the keepalive packet is looped back to the port that sent the keepalive.

     The switch sends keepalives out all the interfaces by default. A device can loop the packets back to the source interface, which usually occurs because there is a logical loop in the network that the spanning tree has not blocked. The source interface receives the keepalive packet that it sent out, and the switch disables the interface (errdisable). This message occurs because the keepalive packet is looped back to the port that sent the keepalive:

%PM-4-ERR_DISABLE: loopback error detected on Gi4/1, putting Gi4/1 in
err-disable state

        Keepalives are sent on all interfaces by default in Cisco IOS Software Release 12.1EA-based software.

         In Cisco IOS Software Release 12.2SE-based software and later, keepalives are not sent by default on fiber and uplink interfaces.

         The suggested workaround is to disable keepalives and upgrade to Cisco IOS Software Release 12.2SE or later.

       Reference : http://www.cisco.com/en/US/tech/tk389/tk621/technologies_tech_note09186a00806cd87b.shtml

Hope this helps

Happy Networking!!!!

Regards

Narendrakumar B

[Mohamed Sayed]

hi narendrakumar1987in ,

i need to know how the switch with that IOS(that has this bug) receive its BPDU(keep alive) on the same interface where generate its BPDU from. while this switch is connected to another switch with only one port, how that ??

kindly advise please

[Amit Shahi]

Narendra,

Thank you for explaining the loopback-error. I just set the "no keepalive" on the interface which was keep getting in err-disable state. Hopefully that should fix the problem. Just for the curiosity can you please explain me when  a device can loop the keepalive packets back to the source interface?

Thank you for your help.

Amit

[legandry2]

Hi narendrakumar1987in

it happened with me again but my software release is 15.2(2r)

what could be the issue in my case?

[Giuseppe Larosa]

Hello Tom,

>> May 20 15:03:17.223 India: %ETHCNTR-3-LOOP_BACK_DETECTED: Loop-back detected on

GigabitEthernet0/2.

there is a known bug about this with the suggested workaround being to disable keepalive on interface

try

int g0/2

no keepalive

What IOS image is running on your switch?

>> crypto pki certificate chain TP-self-signed-1076337536

the switch has installed a certificate that is made of all those strange chars that you see, the certificate is self signed

crypto pki trustpoint TP-self-signed-1076337536
enrollment selfsigned
subject-name cn=IOS-Self-Signed-Certificate-1076337536
revocation-check none
rsakeypair TP-self-signed-1076337536
!

the device generates a pair of keys (RSA keys), a certificate is a way to publish the public key the private key is kept on the device.

This should not be a problem for you

Hope to help

Giuseppe

[felix.barrena.lison]

Hi,

I have a cisco 3560 se Swtich on our LAN that is connected with another cisco 3560 switch. The error:

Jun 21 19:19:26.927 METDST: %ETHCNTR-3-LOOP_BACK_DETECTED: Loop-back detected on FastEthernet0/3.

Jun 21 19:19:26.927 METDST: %PM-4-ERR_DISABLE: loopback error detected on Fa0/3, putting Fa0/3 in err-disable state

I have updated to c3560-ipservices-mz.122-50.SE5 IOS, because the only solution is disable the keepalive.

The problem is that interfaces need not always be up, There another solution to the problem?

[Mohamed Sayed]

hi 

i need to know how the switch with that IOS(that has this bug) receive its BPDU(keep alive) on the same interface where generate its BPDU from. while this switch is connected to another switch with only one port, how that ??

kindly advise please 

[smahaboob_basha]

I faced similar problem and the solution for it was to enter the following commands on the physical interfaces.

keepalive 10

no keepalive