Switch downs second port of LAG when connected

[Kvothe42]

Hi there,

we've got two cisco cbs 350 24p 4x. Since a lot of traffic is going through them, I wanted to connect them via LAG.
Port 23 & 24 on each. As soon as I plug in the cable in the second port, the switch detects a possible loop and deactivates it. 
What follows is a series of up and down, even when the administrative status is set to "down".

I used the manual from cisco to set up the LAG, but somehow that wont do. Something I cant point my finger at, disrupts the setup.

I think I setup everything as it should be. Is there maybe something that needs to be deactivated for this to function properly?
I already took care of smartport config, STP and auto negotiation.

Best regards
Felix

[KJK99]

@Kvothe42 

Have you tried with the flow control disabled? Also, are your switches configured with VLANs?

[Kvothe42]

No, not yet. And yes, they have VLANs. But the two ports I tried to establish the link with, are accessports. I know there is a cli command to clear port config, but my cli does not have the option, when I type "show ?". 

[Kasun Bandara]

@Kvothe42 what are the logs you see when this happens? also try to get console output when issue occurs. and share it here.

[Kvothe42]

It just goes from up to down. 

[Kasun Bandara]

@Kvothe42 can you try remove those ports from LAG and confirm those are working properly without LAG?

[KJK99]

@Kvothe42 

Double check the port configuration. LACP does not like something about it. Make sure the port configuration meets the LACP requirements and is identical on those ports.