Please be a bit more accurate in describing actual topology of your environment.
The internal and external interfaces of VSX units should be connected to the switches (or VLANs), not routers and MDS as depicted in your diagram.
Additionally, your MDS is assigned IP address in the same network as the interfaces connected to the router on the right side, while VSX interfaces connected to it are in a different network.
192.168.43.1 should be assigned to a VLAN interface, if you are connecting to a L3 switch or to the upstream router, if you are connecting to L2 VLAN.