Hi @toanpk. You have a lot of active checks running against the Juniper device, will already create some load. Now Checkmk is very powerful in it’s monitoring, which means, that there is a considerable amount of queries performed. The “Check_MK” service tells you, that there is a timeout. You want to read and understand the following blog post.
Monitoring with SNMP: Troubleshooting in God Mode | Checkmk