Which statement about collision domains and broadcast domains is correct?

Each switch port in Junos operates as an independent half-duplex/ full-duplex Ethernet segment; therefore every port is its own collision domain. Unless VLAN tagging is configured, all ports on the same switch belong to one Layer-2 broadcast domain, so Ethernet broadcasts are flooded to every port.

A. Routers do not forward Layer-2 broadcasts, so they separate broadcast domains as well as collision domains.

B. VLANs segment broadcast domains; they do not reduce collision domains, which are already per switch port.

D. Broadcast domains exist at Layer-2; IPv6 simply uses multicast in place of broadcast, so the domain concept still applies.

1. Juniper TechLibrary, “Understanding Collision and Broadcast Domains,” Junos OS Enterprise Switching, Section: Ethernet LAN Fundamentals (2023-10-23), para. 1-3.

2. Juniper Day One: Switching Fundamentals, Ch. 2 “Layer-2 Forwarding,” p. 24-25.