Which attribute of a host is used to route packs to a non-local subnet?

A host's default gateway is the IP address of a router on its local network segment. When a host needs to send a packet to a destination IP address that is not on its local subnet, it forwards the packet to the default gateway. The gateway is responsible for routing the packet to the next hop on the path toward the final destination. This is the fundamental mechanism for a host to communicate with devices on other networks or the internet. The host determines if a destination is non-local by comparing the destination IP address against its own IP address and subnet mask.

A. VLAN trunk: A VLAN trunk is a network link that carries traffic for multiple VLANs, typically between switches, not a host attribute for routing.

C. NTP server: An NTP server is used for synchronizing system clocks across a network and is not involved in the process of packet routing.

D. DNS server: A DNS server resolves domain names to IP addresses; it does not route the actual data packets to those addresses.

1. NetApp ONTAP 9 Documentation: In the "Networking" documentation for ONTAP 9.13.1, the section on "Configure a default or static route" states: "A default route is used when no other route to the destination is known. Typically, the default route points to a gateway router that can forward packets to the rest of the network." This confirms the role of the gateway for non-local traffic.

Source: NetApp ONTAP 9.13.1 Documentation Center, "Networking > Network and LIF management > Routing and gateways > Configure a default or static route".

2. University Courseware: MIT OpenCourseWare provides lecture notes that explain this core networking principle. In the notes for a course on digital communication systems, it is explained that a host's forwarding table typically contains an entry for the local subnet and a default entry that directs all other traffic to a gateway router.

Source: MIT OpenCourseWare, Course 6.02, "Introduction to EECS II: Digital Communication Systems," Fall 2012. Lecture 20 Notes, Section 20.2 "Routing".

3. Academic Publication (Textbook): In the widely used networking textbook "Computer Networking: A Top-Down Approach," the role of the default gateway (referred to as a default router) is explicitly defined as the router to which a host sends all packets destined for outside its local subnet.

Source: Kurose, J. F., & Ross, K. W. (2021). Computer Networking: A Top-Down Approach (8th ed.). Pearson. Chapter 4, Section 4.4.2, "The Forwarding Table".