Enhanced Interior Gateway Routing Protocol (EIGRP) uses bandwidth and delay as its primary metrics to determine the best path for routing traffic. EIGRP is an advanced distance-vector routing protocol, which is proprietary to Cisco systems, making it highly efficient in a variety of network designs. It can also utilize load, reliability, and maximum transmission unit (MTU) as additional metrics, but bandwidth and delay are the primary considerations in its composite metric calculation. Other protocols listed, such as RIP, OSPF, and BGP, use different metrics like hop count (RIP) and cost based on link state (OSPF), or make decisions based on path attributes and policy (BGP).

MAC address reservation is the technique that allows a device to maintain the same IP address lease based on the physical address of a network card. MAC address reservation is a feature of DHCP that allows network administrators to assign specific IP addresses to specific devices based on their MAC addresses. A MAC address is a unique identifier that is assigned to each network interface card (NIC) by its manufacturer. A MAC address reservation can ensure that a device always receives the same IP address from the DHCP server, regardless of its location or connection time. This can be useful for devices that need consistent network access or configuration, such as servers, printers, or cameras. Reference: [CompTIA Network+ Certification Exam Objectives], How to Reserve IP Addresses with DHCP Server

A broadcast storm is a situation where a network is flooded with broadcast packets, which are sent to all devices on the network. This can consume bandwidth, cause congestion, and degrade performance. A broadcast storm can be caused by improper network configurations, such as loops or misconfigured switches. In this scenario, the old switches may have created loops or failed to filter broadcast packets, resulting in a broadcast storm that overwhelmed the network.

One of the features that can be configured to ensure that GRE overhead does not affect payload is A. jumbo frames. Jumbo frames are Ethernet frames that have a payload size larger than 1500 bytes, which is the standard maximum transmission unit (MTU) for Ethernet. By using jumbo frames, more data can be sent in each packet, reducing the overhead ratio and improving efficiency.
Auto medium-dependent interface (MDI), interface crossover, and collision detection are features related to Ethernet physical layer connectivity, but they do not affect GRE overhead or payload.

VLAN hopping is a type of attack that allows an attacker to access or manipulate traffic on a different VLAN than the one they are connected to. One way to prevent VLAN hopping is to change the default VLAN on a switch. The default VLAN is the VLAN that is assigned to all ports on a switch by default, usually VLAN 1. If an attacker connects to an unused port on a switch that has not been configured with a specific VLAN, they can access or spoof traffic on the default VLAN. By changing the default VLAN to an unused or isolated VLAN, the network administrator can prevent unauthorized access or interference with legitimate traffic on other VLANs. Reference: https://www.comptia.org/training/books/network-n10-008-study-guide (page 308)