Refer to the exhibit. If host A sends an IP packet to host B, what will the destination address be in the frame when it leaves host A?

When Host A sends a packet to Host B, and they are on different networks, Host A will need to send the packet to its configured gateway so it can be routed to Host B’s network. The destination MAC address in the frame as it leaves Host A will indeed be the MAC address of its default gateway, which is the interface on Router R1 that is on the same subnet as Host A.

Given the network diagram, the correct destination MAC address for the frame leaving Host A should be the MAC address of R1’s interface on the same network as Host A, which is BB:BB:BB:BB:BB:BB if R1 is the gateway for Host A.

The previous response incorrectly identified the MAC address of R1. The correct MAC address for the gateway router’s interface, according to the exhibit, is indeed BB:BB:BB:BB:BB:BB. Host A will send the frame with this MAC address as the destination to reach its default gateway (R1), which will then route the packet towards Host B.