Broadcast domains and collision domains are two important concepts you need to understand if you’re preparing for the Network+ exam. I recently added some new simulated performance-based questions in the Network+ premium site and this post includes some of that content.
Broadcast Domains and Collision Domains Sample Question
Here is an example of a performance based question you might see on the Network+ exam.
The following table lists common networking components. The second table lists different types of domains such as a single, multiple, and none. In a drag and drop question, you would be asked to drag the correct choice to the correct location in the first table. Here are three examples:
- None. If you think the hub doesn’t have any collision domains, you would drag None to the location under the Hub in the Collision domain row.
- Single. If you think the hub has a single collision domain, you would drag Single to the location under the Hub in the Collision domain row.
- Multiple. If you think the hub has multiple collision domains, you would drag Multiple to the location under the Hub in the Collision domain row.
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Collision domain | ![]() | ![]() | ![]() | ![]() | ![]() |
Broadcast domain | ![]() | ![]() | ![]() | ![]() | ![]() |
Domain choices
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Broadcast Domains and Collision Domains Sample Question
What type of domains are created by a router? (Choose TWO.)
A. Single collision domain
B. Single broadcast domain
C. Multiple broadcast domains
D. Multiple collision domains
E. No collision domains
F. No broadcast domains
Broadcast Domains and Collision Domains Explanation
Here are some basic definitions:
- Collision domain. A portion of a network where transmitted data from one device can collide with transmitted data from another device. When a collision occurs, both transmissions fail and both devices must transmit their data again. More collisions result in more traffic, and an overall slower network.
- Broadcast domain. A portion of a network where broadcast data from one device can reach all other devices in the same broadcast domain.
These domains are created on network segments. A network segment is a portion of a network that is separate from other portions of a network. In many instances, it is a single cable, such as between a computer and a switch. In other instances, it includes multiple cables, such as between a hub and devices connected to the hub.
Broadcast Domains and Collision Domains Sample Question Answer
The correct answer is C and D (multiple broadcast domains and multiple collision domains).
- Routers do not pass broadcast traffic, so they create multiple broadcast domains.
- Routers also create multiple collision domains.
This graphic shows the full answer:
Devices | ![]() | ![]() | ![]() | ![]() | ![]() |
Collision domain | ![]() | ![]() | ![]() | ![]() | ![]() |
Broadcast domain | ![]() | ![]() | ![]() | ![]() | ![]() |
Broadcast Domains and Collision Domains for a Hub
Hubs forward data they receive on any single port to all other ports. This includes both unicast and broadcast data. A hub creates a single segment, a single collision domain, and a single broadcast domain.
Broadcast Domains and Collision Domains for a Switch (layer 2)
Switches pass broadcast traffic so they create a single broadcast domain.
However, they create separate segments between each device and switch ports. This creates multiple segments and multiple collision domains.
Broadcast Domains and Collision Domains for a Router
Routers do not pass broadcast traffic, so they create multiple broadcast domains.
Routers also create multiple collision domains. Traffic between the router and any other device connected to the router (such as a hub, switch, or another router) creates a separate collision domain.
Broadcast Domains and Collision Domains for a Wireless Access Point (WAP)
A WAP connects wireless devices to a wired network. It passes broadcast transmissions just as hubs and switches pass broadcasts so it creates a single broadcast domain.
Wireless devices transmit data over the air and these transmissions can collide with each other. Because of this, a WAP creates a single collision domain.
Broadcast Domains and Collision Domains for a Wireless Router
A wireless router (or WAP with wireless capabilities) creates multiple broadcast domains and multiple collision domains.
It’s worthwhile looking at the inner workings of a wireless router as shown in the following diagram. The top part of the diagram shows the connections the way you’d see them on the wireless router. The bottom part of the diagram shows the logical way they are connected.
- The switch component passes broadcasts creating a single broadcast domain.
- The switch component creates multiple collision domains for the wired devices and a single collision domain for the wireless devices.
- The router component does not pass broadcasts creating multiple broadcast domains.
- The router component creates multiple collision domains with one collision domain between the WAN connection and the ISP modem, and a second collision domain between the router component and the switch.