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Server E9000 internally loop causing the service down on S7700.

Publication Date:  2014-10-31 Views:  175 Downloads:  0

Issue Description

When the switch board CX310 of E9000 connect the S7700 ,the CPU usage will be very high  and cp-car  have many packets loss alarms,The bandwidth usage of  corresponding interfaces are reaching 100%, When the server connect the switch ,on switch there are many alarms.

Alarm Information

We can see many  high CPU usage alarms ,MAC flapping alarms ,it seems  that there is a loop in the S7700.

Handling Process

Topology is shown below , 2 switchboards  CX310 from 1  server  connect to the core switch S7706,And between the CX310,there is a cable connected them directly ,when I shutdown one of the  interfaces  on  S7706 which is connected to server ,
There are still amount of alarms.

When login the CX310 to check the interface status ,I can see the bandwidth usage is 100% for this 10G port ,
But the strange thing is that another 40GE port on CX310 also has 98% bandwidth usage, so there may be a loop in the server internally.

Root Cause

There is a inner cable for 40GE port between 2  switch board CX310,so there is no need to connect a cable between them.Also on the CX310 switches ,the STP is not enabled  causing the loop between 2 CX310.


By disconnected the cable  or shutdown the  interface and the  alarms disappeared ,everything is recovery .


If  Switch connect to server or other devices ,please make sure that  there is no loop internally  on those devices, or the loop will affect the service on switch.