To enable inter-tenant communication with tenant system, you need to use an external router or a logical tunnel interface.
The other options are incorrect because:
A) Interconnecting EVPN switch is not a valid solution for inter-tenant communication with tenant system.
EVPN (Ethernet VPN) is a technology that provides layer 2 connectivity over an IP network. It can be used to connect different logical systems on the same device, but not tenant systems. Tenant systems are isolated from each other and do not share the same layer 2 domain1.
B) Interconnecting VPLS switch is also not a valid solution for inter-tenant communication with tenant system. VPLS (Virtual Private LAN Service) is another technology that provides layer 2 connectivity over an IP network. It can also be used to connect different logical systems on the same device, but not tenant systems. Tenant systems are isolated from each other and do not share the same layer 2 domain1.
Therefore, the correct answer is C and D. You need to use an external router or a logical tunnel interface to enable inter-tenant communication with tenant system.
To do so, you need to perform the following steps:
For external router, you need to connect the external router to the interfaces of the tenant systems that you want to communicate with. You also need to configure the routing protocols and policies on the external router and the tenant systems to exchange routes and traffic. The external router acts as a gateway between the tenant systems and provides layer 3 connectivity2.
For logical tunnel interface, you need to create a logical tunnel interface on the device and assign it to a tenant system. You also need to configure the IP address and routing protocols on the logical tunnel interface and the tenant systems that you want to communicate with. The logical tunnel interface acts as a virtual link between the tenant systems and provides layer 3 connectivity3.
Reference: Tenant Systems Overview
Example: Configuring Inter-Tenant Communication Using External Router
Example: Configuring Inter-Tenant Communication Using Logical Tunnel Interface