How Do Routers Create A Broadcast Domain Boundary?


Broadcast domains are a powerful tool that routers use to manage traffic. They’re also one of the more complex features of your router, and understanding how they work can help you make better decisions about how to use them. In this article, we’ll explain what broadcast domains are and how routers create them.

What is a Broadcast Domain?

A broadcast domain is a designated area in which all devices within the broadcast domain are allowed to send and receive broadcasts. Broadcast domains are important for ensuring communication between devices in a controlled environment, such as when setting up a home network. Routers create broadcast domains by assigning an IP address to a network interface card (NIC) and configuring the NIC to send and receive broadcasts.

What is a Broadcast Domain Boundary?

Broadcast domains are a set of networks that share a common broadcast domain. A broadcast domain is a specific area in which all network devices can receive broadcasts from each other. Routers use broadcast domains to create a boundary between networks.

Routers create a broadcast domain boundary by configuring the router’s output port to send broadcasts only to devices on the same subnet as the router. When you configure a router to send broadcasts, it creates a broadcast domain boundary.

The output port on most routers is configured with a default address of, which means that the router sends broadcasts to all devices on the network. To create a broadcast domain boundary and send broadcasts only to devices on your subnet, you need to change the router’s output port address.

You can change the output port address on most routers by following these steps:

  1. Step 1: Open the router’s configuration page.
  2. Step 2: Under the Networking tab, locate the Output Interface section and click Edit.
  3. Step 3: In the Output Interface window, locate the Default Address field and enter the IP address of your subnet in this field.

How Routers Create a Broadcast Domain Boundary

Routers create a broadcast domain boundary by using the network address translation (NAT) feature. NAT allows routers to translate an individual computer’s local IP address into a unique public IP address that is used by the router to send packets to and from the computer. Routers use NAT to create a broadcast domain boundary because all computers on the same subnet can view and send packets to any other computer on the subnet. Additionally, routers use NAT to keep unauthorized users from accessing systems behind the router.

How to Remove a Domain from a Router

When you are configuring a router, it is important to understand the concept of domain boundaries. Routers create broadcast domains by default. This means that all broadcasts (packets sent out on all interfaces) will be sent to all devices within the broadcast domain. This can be a problem if you want to remove a device from the broadcast domain.

To remove a device from a router’s broadcast domain, you need to first configure the router to use a perimeter network. A perimeter network is a virtual network that sits outside of the router’s existing network. You then need to configure the router so that broadcasts are not sent out on its external interfaces. To do this, you need to enable routing on the external interface and configure the router’s serial interface as an access point. The device that you want to remove from the broadcast domain then needs to be connected to the access point on the external interface.


Routers create a broadcast domain boundary by filtering packets that are destined for specific machines on the network. Routers use two primary criteria to determine which packets should be forwarded: the destination IP address and the source IP address. By understanding how routers create a broadcast domain boundary, you can better configure your network so that all machines on it can communicate with each other.

Leave a Reply

Your email address will not be published. Required fields are marked *