Cisco Support Community
Showing results for 
Search instead for 
Did you mean: 

Welcome to Cisco Support Community. We would love to have your feedback.

For an introduction to the new site, click here. And see here for current known issues.

New Member

err-disable in ethernet


we are having cisco 2960 switch in our network and we are connected 7902 IP Phone and phones are working but when phone power on and off then that port is down and shown that err-disable, we are also do duplex setting on that port stil we are having same problem so how we can resolve this issues ???


Re: err-disable in ethernet

If you have enabled errdisable recovery, you can determine the reason for the errdisable status if you issue the show errdisable recovery command. Here is an example:

cat6knative#show errdisable recovery

ErrDisable Reason Timer Status

----------------- --------------

udld Enabled

bpduguard Enabled

security-violatio Enabled

channel-misconfig Enabled

pagp-flap Enabled

dtp-flap Enabled

link-flap Enabled

l2ptguard Enabled

psecure-violation Enabled

gbic-invalid Enabled

dhcp-rate-limit Enabled

mac-limit Enabled

unicast-flood Enabled

arp-inspection Enabled

Timer interval: 300 seconds

Interfaces that will be enabled at the next timeout:

Interface Errdisable reason Time left(sec)

--------- --------------------- --------------

Fa2/4 bpduguard 273

One you find the reason, you will be able to fix it.

New Member

Re: err-disable in ethernet


I am not enable errdisable recovery command still it's happen if i am enable then also same .?????

Re: err-disable in ethernet

if the port is err-disabled you can see the reason with:

sh int status err-disabled

New Member

Re: err-disable in ethernet


I cheked "sh int status err-disabled "

and shown that reason "loopback" on interface but the thing is that port coonected to cisco 7902 IP Phone .

Re: err-disable in ethernet

Loopback error

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:

Is the phone directly connected to the switch?

can you post STP related config + interface config

New Member

Re: err-disable in ethernet


Yes IP phone directly connected to switch and particular that port we are facing problem.? can you advice me which type of configuration i have to do ?

Re: err-disable in ethernet

for access port

if a pc is connected to the phone and in a different vlan

switchport mode access

spanning-tree portfast

spanning-tree bpdugard enable

switchport access vlan x

switchport voice vlan y

switchport nonegotiate

Re: err-disable in ethernet

it looks like this is your problem (old document from 2004); 2960 switch is not listed as affected device.

Which IOS are you running?

New Member

Re: err-disable in ethernet


Thank you for this but problem is that we have connected only IPPhone there is no pc ot like that ...only one IPPhone 7902 connected.

Re: err-disable in ethernet

see previous post