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Friday, May 21, 2010

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

We have configured a new cisco 2960 se Swtich on our LAN that is connected with another Cisco switch with trunk with crass cable. The backbone link is down frequtly since we have installed it on network follwing Eror has shown in log

%ETHCNTR-3-LOOP_BACK_DETECTED: Loop-back detected on GigabitEthernet0/2.

Can somebody help us resolve the issue?

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

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:

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.

Please click here for more details on Errisable Port State Recovery on the Cisco IOS Platforms.

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