Detailed Explanation:In a "one-armed routing" setup, a router with sub-interfaces can handle inter-VLAN routing by logically segmenting traffic within a single physical interface. In this configuration, each department (Administration and Finance) is assigned a different VLAN with separate sub-interfaces on Router R1.
In such a setup, communication between different VLANs (i.e., inter-VLAN routing) is handled by the router, even without Proxy ARP enabled. The router can directly route packets between the VLANs as it is aware of the different networks and performs Layer 3 forwarding based on the IP address of each VLAN's sub- interface.
Thus, even if ARP Proxy is disabled, devices in the Administration and Finance departments can communicate through the router because inter-VLAN routing takes place at Layer 3 without relying on ARP proxy functionality.

The Bridge ID, a combination of bridge priority and MAC address, is used to determine the root bridge in STP. The switch with the lowest Bridge ID becomes the root bridge. If bridge priorities are identical, the switch with the lowest MAC address is selected as the root bridge.

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