This post highlights an issue when connecting an S6720 to the server. Please read further down for more details.
There is an issue connecting the switch to the server - after restarting the server, the port of the switch which was connected is staying down.
The switch connected to the server via a Huawei SFP+ Passive cable was experiencing issues after the server had been restarted.
After the server has restarted, the connection to the same port is impossible - the port is staying down and is working only when changing it with another port.
Also, a lot of Auto port-defend logs with the Attack Protocol as ARP-REQUEST are spotted.
Solution
The issue was on the switch that was using the Huawei SFP+ Passive cable (copper). The copper cables should not be used for connecting with any devices other than another switches from the subseries in a stack module.
The fix to this issue was that, in this case, an optical module should be used for the switch connection to the server. This doesn't have any issues because they were designed for this.