When a packet has passed through a router, the _____ of the outbound interface is used as the source, and the MAC address of the next hop router interface becomes the _____ MAC address.

In networking, when a packet traverses a router, there are specific roles that the IP and MAC addresses play. When the outbound interface of a router sends the packet, the MAC address of that interface becomes the source MAC address. This is essential for the delivery mechanism within the local area network (LAN) because devices in the same LAN use MAC addresses to communicate effectively.

The destination MAC address, in this scenario, is set to the MAC address of the next hop router interface. This is crucial because routers forward packets to each other until they reach their final destination. The next hop's MAC address ensures that the packet ultimately makes its way through the correct path.

By understanding these principles, one can see how the structure of the network layer (where the IP addresses operate) and the data link layer (where MAC addresses are used) work together to ensure that data packets are routed correctly and efficiently across networks. The correct identification of these addresses is fundamental for proper telecommunication and data transfer within Ethernet networks.