A simple example is both ends of a single Ethernet patch cable connected to a switch.
In some cases, a broadcast storm can be instigated for the purpose of a denial of service (DOS) using one of the packet amplification attacks, such as the smurf attack or fraggle attack, where an attacker sends a large amount of ICMP Echo Requests (ping) traffic to a broadcast address, with each ICMP Echo packet containing the spoof source address of the victim host.
The initial Echo Request is multiplied by the number of hosts on the network.
[3] In wireless networks a disassociation packet spoofed with the source to that of the wireless access point and sent to the broadcast address can generate a disassociation broadcast DOS attack.
One approach to alleviate the broadcast storm problem is to inhibit some hosts from rebroadcasting to reduce the redundancy, and thus contention and collision.