Solution:

Those 2 jumpers were used for network termination. Here're some information for your reference. A CAN-bus system must be terminated at each end of the trunk line. The host controller and the last CAN-bus repeater or other DeviceNet device on the network must always be terminated to eliminate reflections, even if only two nodes are present. Follow the information below when using an ADAM-4515. Trunk line use: For the purpose of network termination, the ADAM-4515 is treated as the last node on the section of the trunk network to which it is connected. Therefore, when an ADAM-4515 is used directly in a trunk line, it must be terminated on both the Network A and Network B sides. You must also place a terminating resistor on the other end of the device of Network A and on the last device on the Network B side of the trunk line. Drop line use: When the ADAM-4515 is used in a drop line (with the Network A side towards the main trunk), the Network A connection is not terminated. The Network B side is now considered as an independent bus line electrically. The ADAM-4515, as the first node in this new bus line, must be terminated and the last device on the line must also be terminated. So, JP2 for CAN1 end, JP1 for CAN0 end. We should improve the description for easy to use JP1 and JP2. The line is terminated when jumper CLOSE.