Solved: Flapping of member of a port channel causes slow drain .

javedshaikh81 · ‎06-22-2016

We have one port channel configured in our Customer environment. This port channel has been configured with 4x16Gbps ports inside it. One of the switch port started flapping (up & down) continuously, which caused multiple alerts on many hosts as well as drastic performance slowness on one of the Business Critical application. It caused a major issue and later on after disabling this port administratively, the issue got resolved.

Could you let me know the cause of major impact and port-channel behavior in such rare cases, where because of one port flapping, whole port channel got affacted ? Is it a expected behavor of port-channel of kind of software bug in Cisco MDS 9710 switches running SAN OS ?

Walter Dey · ‎06-23-2016

No, error disable also works for E, resp. TE ports:

http://www.cisco.com/en/US/docs/storage/san_switches/mds9000/sw/rel_1_x/1_3/fm/configuration/guide/PortChnl.html

If you misconfigure PortChannels, you may receive the "Error disabled - Possible port channel misconfiguration" message. If you receive this message, the PortChannel's physical links are disabled since an error has been detected.

Please post output of

Switch# show errdisable recovery

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Walter Dey · ‎06-22-2016

What is the root cause of the port flapping ?

javedshaikh81 · ‎06-22-2016

bad cable

Walter Dey · ‎06-22-2016

The port-channel protocol is quite busy, handling a port joining / leaving the PC; this will definitely impact the performance.

javedshaikh81 · ‎06-23-2016

Thanks for your reply walter

My Only concerns is if the port is flapping why it did not go to errdisabled state by itself.

javedshaikh81 · ‎06-23-2016

I am assuming since the port was flapping it could have carried data frames since the portchannel sensed it ok and then after some time it went off and dropped the frames

javedshaikh81 · ‎06-23-2016

Hi, Will this command "errdisable detect cause bit error 5 60s" will help me set port guard on the trunk ports which are portchannel or will it only work on F ports

Walter Dey · ‎06-23-2016

No, error disable also works for E, resp. TE ports:

http://www.cisco.com/en/US/docs/storage/san_switches/mds9000/sw/rel_1_x/1_3/fm/configuration/guide/PortChnl.html

If you misconfigure PortChannels, you may receive the "Error disabled - Possible port channel misconfiguration" message. If you receive this message, the PortChannel's physical links are disabled since an error has been detected.

Please post output of

Switch# show errdisable recovery